The life history of two species of plant-lice inhabiting both the witch-hazel and birch

Material Information

The life history of two species of plant-lice inhabiting both the witch-hazel and birch
Series Title:
Technical series / U.S. Dept. of agriculture. Division of Entomology ;
Portion of title:
Species of plant-lice
Pergande, Theodore, 1840- 1916
Sullivan, Lillie
Place of Publication:
Washington, D.C.
U.S. G.P.O.
Publication Date:
Physical Description:
44 p. : ill. ; 23 cm.


Subjects / Keywords:
Aphids ( lcsh )
Aphids -- Speciation -- History ( lcsh )
Aphids -- Life cycles ( lcsh )
Witch hazels -- Diseases and pests ( lcsh )
Birch -- Diseases and pests ( lcsh )
federal government publication ( marcgt )
non-fiction ( marcgt )


General Note:
"Drawings made by Mrs. L. Sullivan under the writer's supervision"--P. 7.
Statement of Responsibility:
by Theo. Pergande.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
Resource Identifier:
029625126 ( ALEPH )
27915950 ( OCLC )
agr09003101 ( LCCN )
SB945.A5 P47 1901 ( lcc )
595.7 ( ddc )

Full Text

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Entomologist: L. 0. Howard. 'i. .:^
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rst Asstant Entomologist: .C. L. Marlatt. ; ." :"
Assistant Entomoloqists: Th. Pergande, F. R. Chittenden, ftsrlsiteintoop:^^
Ivestigators: E. A. Schwarz, D. W. Coquillett..
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Washington, D. C., July 16, 1901.
SIR: I have the honor to transmit herewith the manuscript of a
short but full paper entitled "Life history of two species of plant-
lice inhabiting both the witch-hazel and birch," by Theodore Per-
gande, an assistant entomologist in this Division. I recommend that
this paper be published as Technical Series No. 9. As explained in
the letters transmitting earlier bulletins of this series, papers of this
character, while only indirectly of interest to farniers, fruit-growers,
and foresters, are of especial value to economic entomologists who are
engaged in making practical applications of scientific entomology.
In the present case plant-lice form a group of insects which are very
destructive, economically considered. Their life histories are very
remarkable and little understood. This is especially the case with
those forms (and they are many) which have alternate food plants.
The practical value of this kind of work was admirably illustrated in
the investigation of the hop plant-louse, carried on under this Division
some years since. In the discovery of the alternation of the food
plants and the exact details of the life history was found a suggestion
for an easy and practical remedy. The present paper well illustrates
the remarkable phenomena which are to be ascertained in this group
of insects and will be a guide to methods of investigation and to the
results to be expected from the study of forms of greater economic
importance, although one species here considered has in fact been
known to kill young birch trees.
Respectfully, L. 0. HOWARD,
Secretary of Agriculture.

Digitized by the Internet Archive
in 2013


Introduction .--------------. ---------------- .------.-- ------------ 7
Hormaphis hamamelidis Fitch ----------------------------------------- 9
First generation ..--- .......------------.---. -..---------..--..- 10
Second or migratory generation---.-. ...----------------------...... 13
Hamnamelistes spinosus Shimer -......------..---------..---.. -- -- 25


Fig. 1. Hormaphis hamamelidis. galls .....---...-----.-................... 10
2. Hormaphis hamamelidis. young larvae on bud, young stem-mother.
antenna, etc . --. --. --..----.. ---.-...-.-.-......... 11
3. Hormaphis hamamelidis, second stage of stem-mother .-.-- 12
4. Hormaphis hamamelidis. adult stem-mother .----.-...-..--- 13
5. Hormaphis hamamelidis. second generation, young larva, pupa,
migrant .... .. ---.. .. .. .. .. .......--- ---- - 14
6. Hormaphis hamamelidis. third generation, young larva- ...----.. 17
7. Hormaphis hamamelidis, third generation, third stage ............ 18
8. Hormaphis hamamelidis. third generation, fourth or final stage... 19
9. Hormaphis hamamelidis. sixth generation, second stage----- ...-----... 21
10. Hormaphlis hamnamelidis. sixth generation, return migrant ........ 22
11. Hormaphis h imamelidis, sexual generation .. -. .......... 22
12. Haminamelistes spinosus. winter eggs, eggs in position on flower buds- 27
13. Hamamelistes spinosus. twig of witch-hazel with young galls .... 28
14. Hamamelistes spinosns. mature gall-- ..--------...----------. 29
15. Hamamelistes spinosus. mature stem-mother ......---.......--- 30
16. Hamamelistes spinosus. spring migrant ......................... 32
17. Hamamnelistes spinosus. hibernating larva, antenna, etc------.. 34
18. Hamameli.stes spinosus. adult female, third generation.--.-. .---- 35
19. Hamamelistes spinosus, pseudo galls or corrugations on leaves of
birch ................ . ....... ..... ......... ...... . 36
20. Haminamelistes spinosus. young larva, fourth generation -------. 37
21. Hamamelistes spinosus, young larva, first stage, fifth generation .. 39
22. Hamamelistes spinosus, young larva, sixth or sexual generation.. 42
23. Hamamelistes spinosus, male and female antennae -------------..... 43


The study of the life history of the Aphididm or plant-lice, in con-
nection with their peculiar and frequently destructive habits as well
as the remarkable traits of many of the species, has offered a most
fascinating field for research and study to many naturalists, and their
labors have brought to light numerous interesting facts regarding the
habits and economy of various species. Much is still to be learned
concerning the annual migrations and the intermediate habits and
changes of the majority of our P-,mphigini, the architects of galls or
excrescences on the leaves and other portions of certain trees and
shrubs, which they desert, at the opportune time, to vanish com-
pletely from sight. These migrations and sudden disappearances of
the gall-makers leave the observer in doubt as to the whereabouts of
the connecting links of the fleeting migrants, of which very few have
thus far been discovered. During autumn and early winter the
return migrants make their r appearance, as suddenly and mysteriously
as the spring migrants disappear, without bearing a clue as to their
former habitations. This is for the purpose of restocking their origi-
nal ]lost plants with their eggs, 14) enable the species to commence a
new cycle of existence the followiing- spring.
Interesting as the life history of all these inse(cts is, there are few
or none among them which have a more remarkable or a more diver-
sified cycle of existence th an two species belonging to the genera Hor-
mapli.. and H(nin elsi.s/'s, both of which, alternately, inhabit the
witch-hazel, Hmnminelis rirgiliira, and the birch, Bef ida nira. The
study of the life history of these, after numerous failures and disap-
pointments, covering a space of nearly twenty-two years of patient
labor, the writer has been fortunate to bring to a successful conclusion.
The drawings were all made by Miss L. Sullivan under the writer's
The synonymy of the oldest of the two species, as it will now
stand, is:
Hormaphis hiamamelidis Fitch.
Byrsocrypta hainamelidis Fitch, N. Y. Cat. of Horn. Insects, 1851, p. 69.
Hormaphis hamamelidis Osten Sacken, Stett. Ent. Zeitung, 1861. p. 422.
Hormaphis hamamelidis Walsh. Proc. Ent. Soc. Philad., VI, 1866-67, p. 281.
Hamamelistets cornu. Shimer, Trans. Am. Ent. Soc., I, 1867, p. 283.
Hormaphis hamamnelidzs Thomas, Trans. Ill. State Hort. Soc., 1876-77, p.

The earliest, a rather brief record and description of this interest-
ing Aphid, was published by Dr. Asa Fitch in 1851, in his "Cata-
logue of the IIomniopterous Insects of the State of New York," under
the name .of Byrsocrypta hamnamelidis. Ten years later it was
redescribed by Baron von Osten Sacken in the Stettiner Entomologische
Zeitung (p. 422, 1861), under the generic name of Horinaphis, using
the identical specific name adopted by Fitch, though not being aware
of its having been described by Fitch under the same name, and
erecting for it a new genus. A translation of this description, by B. D.
Walsh, will be found in the Proceedings of the Entomological Society
of Philadelphia, 1866(-67 (p. 281). In 1867 it was again described by
Dr. Henry Shimner, in the Transactions of the American Entomolog-
ical Society of Philadelphia (vol. 1, p1). 283), under the name of Hama-
melisle.s corniu, with a rather full description of the gall and its archi-
tects. Excepting a short description of the gall and the winged insect,
by Prof. Cyrus Thomas, in the Transactions of the Illinois State Hor-
ticultural Society for 1876, published in 1877 (p. 199), nothing addi-
tional regarding the history of this interesting species has been
The writer's observations regarding this species were begun at
Washington, D. C., in the spring of 1878, and were continued with
varying success ::ntil the end of 1S99, when they reached a successful
termination( n.
As with other gall-producing plant-lice, the study of the galls and
their architects is comparatively easy, but, with the departure of the
winged minigrants, contilnuIous observations are suddenly interrupted
and the track lost, leaving no trace as to the whereabouts of the inter-
mediate generations. Migration irom the host plant takes place gen-
erally during spring or summer, th,. i rurn migritnts making their
reappearance from early in September ti .1 late in the fall, to restock
their host with eggs.
What becomes of this particular species during the intervening
time after leaving its gall remained a profound mystery to the writer for
many years, notwithstanding continuous efforts to solve the problem.
Accidentally, while on a collecting trip near Tacoma, D. C., in Sep-
tember, 1890, the writer observed a peculiar Aphid inhabtiug the
under side of the leaves of a small shrub of Betuliu nigra, b-it failed
at that time to recognize it as the missing link of Hormaphis. During
the following seven years nothing additional was discovered to cause
me to continue observations, this being due in a great measure to the
destruction of large numbers of witch-hazel bushes and young birches,
and the consequent scarcity of galls in the woods surrounding the city
of Washington. Fortunately, however, I discovered in September,
1897, a number of witch-hazel trees and bushes, as well as young
birches, in a narrow and protected valley near the edge of a small
creek at Cabin John Bridge, Md., where I found numerous old and

dry galls on the leaves of the witch-hazel. Here I began again my
search for the evading generations of this species, and in examining
the leaves of birches rediscovered on many of them the same peculiar
Aphid which had previously been found at Tacoma. It was in
various stages of development, including the winged migrants, which
proved, after a thorough examination and comparison with the spring
migrants of the witch-hazel, to be identical with Hormaph is hawma-
melidis. To be sure of no mistake an examination was made of the
leaves of witch-hazels near the birches with the result that the under-
sidec of numerous leaves was found to be almost completely covered
with larvam of various stages, and among them numerous specimens
of the migrants from birch, actively engaged depositing their progeny,
which later on proved to be the sexual generation. This settled the
previously ol)scure question as to the secondary host of the intermie-
diate generations, and enabled me to continue and to complete my
pr( tracted observations of the life history of this remarkable little
species and the strange transformations it undergoes on the birches,
which will be recorded in the following pages.


(Tall (Fig. 1).-The more or less rapid development of the galls pro-
Iduced by this species on the leaves of the witch-hazel depends entirely
on the advancement or retaliation of the season. In the latitude of
Washington, D. C., they usually start about the middle of April,
attaining their full growth and development toward the end of May.
To be in time and ready for the duty assigned to them by nature, the
young stemi mothers hatch about :t week or more in advance of the
appearance of the young leaves, when they frequently congregate in
considerable numbers on the still closed buds, patiently awaiting
their bursting. During this critical period maiiy of them perish,
either for want of food or from the inclemency of the weather. The
survivors settle at once on the underside of the tender and unfolding
leaves, generally along the midrib or the lateral veins, and insert at
once their sucking bristles into the tender substance of the young
leaf. The presence of the young gall-maker soon becomes apparent on
the upper side of the leaf by a pale yellowish-green discoloration, and
within a few days the first symptoms of the growth of the new gall
are observable in a small, blister-like swelling on the upper side and
a corresponding depression beneath. From now on the development
of the new gall is quite rapid, in order to keep pace with the growth
of the leaf, so that at the beginning of May they have become quite
convex or slightly conical above with the underside almost closed and
protected by numbers of rather stiff, white, and radiating hairs to
prevent the entrance of enemies. The color of these young galls,
above and below, is of a greenish yellow, with the most elevated
portion of a more or less pronounced vinous shade and surrounded


at base with a purplish or vinous ring, which is also more or less dis-
tinct on the underside. By the middle of May the galls are about
two-thirds grown, showing the peculiar conical formation clearly and
reaching full development toward the end of May, when they measure
from 10 to 12""1 in length by4 or 511"1 in diameter at base. They are
obliquely conical, or of the shape of a dog's tooth, and somewhat con-
stricted at base, the underside forming an elevated and rather stout
rim around the more or less circular opening which is densely covered
with a pale pubescence. The opening has by this time become large
enough to allow the migrants to escape. They are now of a firm,
leather-like consistency and of a uniform pale yellowish-green or
greenish-yellow color.
If not numerous, as in
some years, there is
generally but one or at
4 most two galls on a
leaf, whereas in favor-
-able years there may
6 be from two to eight or
more galls on a single
S /,f / eaf, which then be-
coites more or less
/ ^ dwarfed and much dis-
torted. These galls,
/ even after their archi-
/ _._ I- tects have departed,
I /-) ~remain fresh and suc-
culent for a considera-
ble length of time, but
gradually turn brown
a and dry up.
Itinter f~q y.--The
FIG. I.-Hornuphis hatiuinamelidlis: t, galls, natural size: ib, sev- iter e .-The
tion of gall-much enlarged (original). winter eggs of this
Aphid, as in someother
species of plant-lice inhabiting trees and shrubs, are deposited on the
branches and twigs, especially those bearing the leaves, and generally
around or near the base of the buds or near the scars left after the
dropping of the leaves in October, or as late as any of the leaves bear-
ing the sexed generation remain on the shrubs. The eggs resemble
greatly those of Aphis mnali, though they are considerably smaller, and
measure about 0.,2mn in length. They are of a slightly pyriform shape,
bluntly pointed at the posterior end and highly polished, being at first
yellowish or orange but changing gradually to a deep black.

Sflem-mother, first stage (Fig. 2).-The young stem-mother on hatch-
11ng is ]Mt slightly larger than the egg, and makes her appearance

about the middle of April, generally about a week or so in advance
of the appearance of the young leaves, during which time they con-
gregate on the buds, on some of which I observed as many as 24 larvae.
Many of-themn doubtless perish before the leaves burst forth. They
are of a dull black color, covered with a delicate film of a slightly
bluish secretion. The eyes are dark purplish and the antenna and
legs blackish. They are provided with short, stout, and truncate
dorsal and lateral secretary tubercles or pores, of which there are
about 18 to 20 on the upper surface of the head, 2 medio-dorsal groups
of 6 to 8 on the prothorax, a group of 4 to 6 pores or tubercles each
side of the median line of the meso- and metathorax, and 1 or 2 pores
each side of the median line on the abdominal segments. There are
also about 8 pairs of tubercles
along the front margin of the (
head, half of them ventro-lat- ,
eral, I or 6 each side of the tho-
racic, and 2 each side of the ab-
dominal segments, with an equal -
number on the ventral side near
the lateral margin which, when c
the insect is living, can not be j
seen from above. From each of
these pores or tulbercles issues .-
a. rather stout and straight, or 0 a
slightly curved, transparent and 1(1c
iridescent white and truncated I' d
waxy rod. which gives to the d,
insect a rather bristly, though ~ "
pretty, appearance.-
The dorsum is but slightly e -
convex and surrounded with a P'G. 2.-Hormaphis /ia.ntrmci.ii.: o, twig and
groove-like depression near the bud with young larvae in position: b, young
ma n. Te ae r stem-mother; c, iantenna: d, tarsus: e, ros-
margin. The antenna are three- trum; f, waxy rod-much enlarged (origin. al).
jointed, with the third joint much
the longest, which is rather more than twice the length of the two
basal joints combined and about as long as the hind tibie. It grows
slightly stoutest toward the end and is indistinctly and irregularly
annulated, bearing one or two short and colorless, movable, sensorial
thumbs near the apex, and two or three short, stiff bristles at the tip.
The legs are rather stout and long, and all the tarsi provided with
four long and capitate digitules, of which the upper pair are longest.
There are also two long and stout backward-curved bristles near the
apex of the posterior tibiae, one or two such bristles about the middle,
externally, of the second joint of the hind tarsi, and a finer and straight
bristle at the apical angle of the first joint. The rostrum is long and
reaches 1)eyond the base of the abdomen, the third joint being very


long and slender, with its basal section bulbous. Before attaining
* maturity the young stem-mothers cast three skins, which are usually
crowded into the opening of the gall, each stage lasting about a week,
the last skin being cast between the 15th and 20th of May.
Stem-mother, second stage (Fig. 3).-The young stem-mother, after
having cast her first skin, measures between 0.4 and 0.6mm in length,
and has become much stouter and of a broadly oval shape. She is
dark purplish or almost black, with antennae and legs paler; she is
slightly pruinose and provided each side of the abdomen with a brush
of white and glistening secretion, which grows gradually longer as
she advances in age, though lacking entirely the characteristic glassy
rods on the back and sides of the young larvae. The antennae are
still of about the same length as in the first stage, though the third
joint is either of a uniform thickness or slightly stoutest at base and
without any annulations. The rostrum has become much shorter and
stouter and reaches barely to the median
coxTe. The digitules of the tarsi and the
f bristles of the posterior tibiae and tarsi have
become much shorter and finer, while the
( digitules have become simple. All secretary
: ) .( tubercless or pores have disappeared, except
}-f three or four at each side of the abdomen,
}r __--_ which, however, are less prominent than in
= the young larva, and become entirely obsolete
*1 -/ in the cast skin.
Stem-mother, third stage.-After casting a
Fin. 3-Horlnafphis a,.umeli- second skin she measures from 0.7 to In1n in
dis: Second stage of stem- length. She is again stouter than before
mother, ventral view-much and contains already a number of partly
enlarged (original i.
developed embryos. She is dark purplish or
brownish and is covered with a mealy secretion, giving her a pruinous
appearance. There are now also apparently six or seven rows of
more or less confluent tufts of a white and glistening, straight, and
evenly shorn secretion each side of the dorsum, directed toward the
median line. The antennae and legs are very similar to those of
the previous stage, except that the third antennal joint has become
stouter at base and more distinctly tapering. The digitules, espe-
cially those of the posterior tarsi, are longer and stouter, though
apparently simple, and the bristles of the posterior tibiae and tarsi
more prominent. Otherwise they are very similar to the larvae of the
second stage.
Adult stem-mother, fourth stage (Fig. 4).-About the middle of
May the young stem-mother casts her third or last skin, and soon
alter having matured proceeds to produce her progeny and continues
to do so during the following three or four weeks, or till about the
middle of June, until her stock of larva is exhausted, depositing from


4 to 6 or more each day until, by the commencement of June, each
gall may contain from 100 to 120 of her progeny in various stages of
development, which, after casting several skins, acquire wings and
gradually depart in quest of their appropriate food plant provided
by nature for their offspring. The adult stem-mother, after having
cast her last skin, measures from 1.2 to 1.4"" in length, and is at first
of a broadly oval or pyriform shape, being broadest near the end of
the abdomen and slightly tapering toward the head, increasing grad-
ually in diameter during the increase of and development of her ova
until she becomes almost globular. She is of a dark purplish color,
with the eyes black and the antenna and legs dusky. At first she is
dusted with a white, powdery secretion, which is soon followed by a
rather long, white, and shaggy secretion, covering almost the entire
abdomen. This secretion is, however, gradually more or less com-
pletely lost as the oc-
cupants of the gall in- __
crease in numbers, be-
ing rubbed off by the tAX
movements of the in- ) T^
habitants as well as by
coming in contact with .
the walls of the gal land
the globules of ejected --- :. ..
liquids which gradu- -..*". ,-_ --"
ally accumulate. The |. ...-.
antennae and legs are -
very similar to those 6 a
of the third stage, al- Fim. 4.-Hormnaphis hamamelidis: a, adult stenm-mnothlier, dor-
though the digitulesap- sal view; b, ventral view; c, antenna-much enlarged
&> T .,,1 (original).
pearto be slightly capi- original).
tate. Those of the claws. are very fine and about the length of the
claws. The rostrum is short and stout and reaches only between
the anterior and median coxin. There is now a distinct, though
rather short and broad, almost semicircular tail, bearing two fine
bristles, while the last abdominal segment, which is more or less com-
pletely covered by the tail, has become distinctly bilobed, each lobe
being provided with two stout bristles arising from small tubercles,
the edge of both sides being also lined with small spines. After being
completely exhausted and empty of ova the stem-mother shrivels up
and dies.

The development of the second generation, or progeny of the stem-
mother or gall-maker, is more rapid, and is completed within sixteen
to twenty days, all of which prove to belong to the migratory form.
The earliest of these migrants make their appearance toward the end


of May or early in June; the remainder leaving the galls gradually
till the end of June or early in July, by which time the last ones have
disappeared. Frequently, however, a few stragglers may be met with
as late as the end of July issuing from belated galls, the product of
a few stem-mothers, hatching from eggs deposited very late in fall
during an exceptionally favorable season.
There is but a single migratory generation in each gall, all of which,
after casting four skins, become winged and leave the gall after hav-
ing fully matured and migrate to birches, where they deposit their
larve on the underside of the leaves, which, in favorable years,
become frequently covered with migrants. So keen and unerring
must be the instinct of these migrants to discover their secondary



c' a

Fio. 5.-Iorinnaphis hanainu elidis: Second generation; a. young larva; b, pupa: c, spring migrant;
f, antenna.-Much enlarged (original).

host that they frequently fly great distances in search for birches,
which may not be growing in the immediate neighborhood of witch-
hazels, as is the case in some localities along the shore of the Potomac
River, which they are compelled to cross in order to reach young
birches on the opposite shore.
Second generation, first stage (Fig. 5).-The young larvae of this
generation are at first pale purplish and slightly covered with a white
powder; they soon change to a dark purplish-brown, the eyes are
black, and the antenna and legs pale dusky. They measure about
0."p"n in length, and are of a regularly oval shape; the front of the
head is almost straight, and the surface of the body appears to be
densely granulated. There are two rather long bristles on the front

of the head, two each side of the thoracic, one each side of the abdom-
inal segments, and two at the end of the body, all of them arising
from a small tubercle. The rostrum is stout and reaches nearly to
the posterior coxme. The antenna are rather short and stout, barely
reaching to the mesothorax; each of the two basal joints bears a long
and stout bristle; the third joint is slightly curved inward and of
almost equal thickness or slightly clavate with the apex, which bears
two or three small bristles, bluntly rounded; its surface is faintly
aunulated or scaly; there are from one to three minute sensorial
thumbs near its apex. The legs are stout and rather long; the digi-
tules are simple, or faintly thickened toward the end, the lower pair
of which is wanting.
Second generation, second stage.-The larve in the second stage are
about twice as large as in the first and more elongated, with the
antenna longer and stouter; the third joint is slightly tapering and
without any traces of annulation; the rostrum reaches only the median
coxai. In general appearance and coloration they are identical with
the young larve.
Second genera ion, tlh ird stag(.-In the third or semipupa stage they
are 0.7 to 0.8"'"' in length and considerably stouter than before and
of a purplish-green, with the head and rudimentary wing pads of a
dirty greenish-white, eyes brown, and the antenme and legs whitish
or faintly dusky. The future wing padls are now represented by
rather prominent, rounded swellings. The antennae are still longer
and stouter than in the previous stage; the third joint is straight and
somewhat tapering and the sensorial thumbs minute. The rostrum
reaches nearly to the median coxae. Front of head somewhat concave.
Second generation, pup a orfourth stage.-The fully developed pupa
varies between 1 and 1."11111 in length. They are of a dark purplish
color, with the eyes dark brown and the antenna, legs, and wing pads
whitish. Front of head straight or slightly convex. The rostrum is
short and stout, and reaches but slightly beyond the anterior coxw,
Antenna and legs similar to those in previous stages, though propor-
tionately longer. The third antennal joint is very long and stout,
slightly tapering amld slightly curved, and bears from one to three
minute sensorial thumbs. All of the pupas, if not rubbed, are fur-
nished at each side of the abdomen with a dense brush of a white and
hair-like secretion.
Second generation, migratory or fifth stage.-The mature migrants
vary somewhat in coloration; they are generally of a dark purplish,
purplish-brown, or black color, though frequently purplish-red or dark
greenish-brown, with antenna, thoracic lobes, and legs black. The
wings are colorless or faintly dusky, the costal cell and stigma brown-
ish, and the veins black. They measure from 1.2 to 1.6"mm in length
and have an expanse of wings of 4 to 5n"m. The wings are carried flat in
repose. Antennaw three-jointed, rather short and slender. The two


basal joints are very short and subequal in length; the first joint is
cylindrical and obliquely truncate at the apex, while the second joint
is almost globular. Joint three is very long in comparison to the two
basal joints and five or six times as long as either of them. It is of
uniform diameter and bluntly rounded at the apex, where it bears
two or three short hairs, and deeply divided by thirty to thirty-six
more or less regular or complete annulations, without a trace of divi-
sions into separate joints. The legs are slender and almost destitute
ot hairs, which are somewhat more numerous and spine-like toward
the end of the posterior tibiae. There are four slender, subequal, and
capitate digritules on each tarsus. Stigma long, narrow, lanceolate,
and as broad as the costal cell, its basal angle almost obsolete. Veins
simple; the second discoidal arises in front or beyond the middle of
the first discoidal vein, though occasionally both start from the same
point. The basal third or more of the third discoidal is obliterated.
Stigmal vein short and almost straight. In the hind wings the second
discoidal is generally wanting, frequently a stump of it or the entire
vein may be observed arising from the first; sometimes both may
start from the saint, point, though in rare cases both are normal,
arising some distancee from each other, and almost parallel to each
other. The head is slightly convex in front. The rostrum is short,
reaching but slightly l)eyond the anterior coxa1. Tail small, knob-
like, bearing six to eight short hairs; last abdominal segment bilobed,
each lobe provided with five or six hairs. There is also a small,
blackish tubercle each side of the anterior four segments of the
After feeding for some time on the juices of the gall, in order to
become fully manture andl strong enough for migration, and also to
hasten the (ldevelol Iient of the embryonic larvae, they abandon their
old home in search for the appropriate food plant for their progeny,
to insure the l)per(petua;tion of their race. Each of these migrants con-
tains about fifty larva', which, after reaching the birches, are deposited
on the under side of the leaves; on reaching the birches they deposit
from six to eight larvae each day until their stock of larvm is exhausted,
after which they shrivel up and die.
Third gen ration, first stacfe (Fig. 6).-Young larvae of this gen-
eration were first ob()served during the first days of June and the first
mature and apterous females on the 18th of the same month, the
insects accomplishing all their changes within fourteen days. The
young larvae are at first of a pale yellowish color, but soon change to
a brownish yellow; the eyes are dark purplish and the antennae and
legs colorless. The young larvae are very small, barely 0.2mm in
length and broadly oval; the abdomen is comparatively small in pro-
portion to the size of the larvae and only about one-third the length
of the entire insect. The entire margin of the body is studded with
short and stout secretary tubercles; sixteen of which are along the

front edge of the head; about five or six each side of the thoracic
segments, two each side of the abdominal segments, and seven or
eight to ten on the last or eighth segment; from each of which issues
a short, stout, truncated and cylindrical, glassy, transparent, and
beautifully iridescent, waxy rod. There is also a series of similar
though shorter rods along the middle of the back. The rostrum is
stout and reaches to or between the posterior coxa. The antenna
are rather long and slender, and about as long as the posterior tibia;
they are faintly serrate or annulated and slightly clavate, with a notch
near the apex, containing a small, movable thumb; the tip is bluntly
rounded and bears two or three small hairs. Legs rather long and
stout; the posterior tibiae bear one or two rather long bristles and the
tarsi a similar one on its external edge. The upper pair of digitules
are long, slender, and capi-
tate; the lower pair is want- .-s-- <
ing. A
Third generation,, .-SCO'nd
stage.-After having cast. their /
first skin the larvae measure
about O.411 in length and
have become proportionally
broader. The antenna have -.
become now very short, almost
rudimentary, and composed( 1 "
of two, or sometimes three, /
more or less distinct joints,
the last or last two joints, as,
the case may be, being about
twice the length of the first, FIG. 6.-Hormaphis hamamelidis: Third geuerntion:
young larva, ventral view-much enlarged (origi-
obliquely truncate at the nal).
apex, and bears a minute
thumb at the inner apical angle. The tarsi of the anterior and
median legs have been lost or they may sometimes be represented by a
minute rounded stump. The tarsi of the posterior legs are deformed;
their claws are lost or represented by a small spine-like process. The
digitules are still present, though simple. The rostrum is stout and
reaches to the meta-sternum. The number and arrangement of the
secretary tubercules are about the same as in the first stage.
Third generatcdion, third stage (Fig. 7).-In the third stage they are
broadly oval; the antenna have become still shorter, while the ros-
trum reaches only between the median coxae. In other respects they
are similar to the previous stage.
Third generation, fourth or Aleurodiformn stage (Fig. 8).-Toward
the middle or end of June the insects cast their third or final skin and
assume a most remarkable mimicry; in fact, mimic now so closely
3504--No. 9-01- 2


certain Aleurodids that for some time I was completely deceived as
to their true nature, which only after close examination of numerous
specimens, in connection with its earlier stages, was disclosed. When
seen on the leaves they are to all appearance true Aleurodids, both in
shape and size, resembling to some extent the scale-like form of Aleu-
rodes corni or related species. At first they are pale brownish, but
change gradually to a dusky or black color. TJhey are almost circu-
lar, flat, and rather coarsely rugose above, with the ventral side quite
convex, and measure, when fully mature, about 0.61,"1 in length and
are surrounded by a rather long fringe of cylindrical, waxy rods; the
basal one-third or one-fourth of these rods is perfectly white, while
the remaining two-thirds or more is glassy and iridescent. There is
also a medio-dorsal group of rather long rods, identical with those of
the lateral margin, which are curved in various ways; all of which,
combined, give to the insect a
a 6 peculiarly pretty appearance.
-Ic CP<>- If denuded of the waxy rods
\ oj there is seen a continuous dou-
ble row of stout secretary tu-
Y. y. bercles surrounding the body
/ excepting the free and movable
"^ -\ terminal segment. The dorsal
i j .. tubercles are irregularly ar-
--- ranged along the middle of the
-i back and vary considerably in
-----f /_ _---- the number in each of the va-
~-^ rious groups.
Occasionally one or two tu-
Flo. 7.-Horimaphishaniaimelifldx.: Third generation. bercles or pores may be oh-
third stage: larged originallyl. served ear the posterior mar-
gin of the head. There are
five to fifteen on the prothorax, six to twelve on the mesothorax, five
to eight on thei metathorax, three to five on the first abdominal seg-
ment, two or three on the second, and one or two on the third segment.
The antennae in this stage have become extremely minute and rudi-
inmentary, and are either one or two jointed. The rostrum is short
an(d reaches but slightly beyond the anterior coxa'. The legs are
as in the larval stages. The tail is very small and knob-like, and
bears two short bristles. The last segment is bilobed and completely
hidden by the semicircular, penultimate segment; each lobe of it
bears five or six bristles, arising from a smalltubercle. In this stage
they are perfectly stationary, as in Aleurodes, and tightly cemented
to the leaf, so that it is almost impossible to remove them without
Fourth and fifth generation, or the second and third Aleurodijform
generation.-The following two generations-the fourth and fifth-


are in every particular essentially identical with the third generation.
Both of these generations are also Aleurodiform, differing but slightly
either in coloration or size from the two preceding generations, obvi-
ating, therefore, the necessity of repeating their cycle of transforma-
tions. The fifth generation attains maturity about the middle of
August or later, and gives birth to larvae of the sixth generation. The
number of larvae deposited by individual femialehs of the Aleurodiformin

FIG. 8.-Hormaphis hamamelidis: Third generation, fourth or final stage; a, dorsal view; b,
ventral view; c, lateral view: d, dorsal view, showing arrangement of pores; e, end of body-
much enlarged (original).

generations is extremely variable. Many of these females are com-
pletely devoid of ova and die soon after attaining maturity; others
may deposit one or a few larve, while the most prolific deposit from
ten to fifteen or more.
With the appearance of the sixth generation a new cycle of forms
begins to make its appearance, in which the aspect of the insects has
changed completely, so muchl so that the casual observer would fail


to trace a connection between them and the Aleurodiform genera-
tions. Continued observations, both in the woods and on small,
potted birches to which the insects were transferred, removed, how-
S ever, all doubt as to the close relationship of these aberrant forms.
This generation develops in time into the return migratory generation.
Sixth generation; return migrants; first stage.-By the end of
August or early in September the females of the last Aleurodiform
generation, after having become fully mature, proceed to produce a
supplementary generation of larvae, and continue to do so until
exhausted. The number of larvFe produced by each female varies, as
in previous generations. As a rule, however, they appear to be more
prolific, since I have observed in one female about thirty embryos, in
consequence of which, in favorable years, the underside of the leaves
of birches may become completely covered with larvm of them in vari-
ous stages of development.
The recently deposited larvae are barely 0.2I"" in length, oval, and
of a yellowish-brown color, changing gradually to purplish-brown,
with antennae and legs whitish. They are at first naked, but soon
become covered with a pruinous or bluish-white secretion, giving
them a moldy appearance. After growing forsome time, there forms
a broad, medio-dorsal stripe of evenly shorn, dense and bristly, white
and iridescent threads of waxy secretion. A dense fringe of similar
glistening threads surrounds also the entire body, leaving the subdorsal
region each side of the median line bare or only covered with a powdery
secretion, and look now quite unlike the Aleurodiform generations.
They are rather convex; the head is narrower than the thorax and
arcuate in front; eyes larger than before; abdomen small or only
about one-third the length of the entire insect. The number and
arrangement of the tubercles surrounding the body is as in previous
generations. In addition to tubercles, there are now two median
groups of two or three very distinct pores or tubercles on the head
slightly in front of the eyes, four medio-dorsal groups of three to five
p.)res or tubercles on each side of the thoracic, and two groups of one
to three pores each on the abdominal segments except the last.
Antennae, legs, and rostrum are very much as before. The third
antennal joint is fusiform, slightly annulated, and bears from one to
three minute thumbs near the apex. The upper digitules of the
tarsi are slender and distinctly capitate. The lower digitules are
Sixth generation; second stage (Fig. 9).-Length of body, 0.4 to
0.6""'. In coloration and general appearance they are similar to
larvae in the first stage, though they are considerably larger and
stouter in proportion, with the sides of the pro- and mesothorax con-
siderably swollen. They are now densely covered with a white and
glistening, straight and evenly shorn, hair-like secretion, issuing from
large, more or less confluent medio-dorsal and lateral compound
glands or tubercles, which, on the abdomen, form broad, transverse

bands, giving them a peculiarly bristly or hairy appearance. The
antenna are very stout, much longer than before, and distinctly
tapering. The rostrum is stout and reaches between the anterior and
median coxe. Legs as in previous stage, though longer and stouter.
Sixth generation; third or pre-pupa stage.-Length of body, 0.6 to
0.8rmM. In this stage they are also densely covered with hair-like
secretion resembling still to a great extent the second larve, except
that they are still larger and stouter, and that they have already
acquired wing pads. The antenna are now very long and stout, the
third joint being longer than the posterior tibie, slightly tapering
and without a trace of annulation, and with the usual movable thumb
and three stiff bristles on the apex.
Six-th generation; fourth or pupa stage.-Length of body, 1 to
1.6mm. They are in every particular like the pre-pupa, except that

1. -

0 o.

a b
Fia. 9.-Hormaphishamamelidis: Sixth generation, second stage: a, duoral view; b, dorsal view
denuded, showing arrangement of pores-much enlarged (original).

the wing pads and the antenna. are still longer, and that the annu-
lation of the third joint of the future imago may be more or less
distinctly seen through the transparent skin. They are of the same
dark color as before, with the head and prothorax paler, and the
eyes, thoracic lobes, and wing pads blackish. The digitules are appar-
ently simple and bristle-like.
Sixth generation, fall migrant (Fig. 10).-Having cast their fourth
or final skin, they acquire wings and, after feeding for some time to
attain complete maturity, forsake the birch and migrates back to
witch-hazel to deliver themselves of the ultimate or sexual generation.
Each migrant, according to size, contains from seven to fifteen or per-
haps more larvae. Migration continues for about a month and a half,
according to conditions of the season and other natural causes, and
commences usually toward the end of August and terminates during
the early part of October. In general appearance they are essentially


the same as those of the spring migrant from the witch-hazel, though
they are uniformly smaller and measure from 0.8 to 1.4"11"111, or rarely
1.6An11 in length, with an expanse of wings varying between 3 and

PFI. 1lI.-orm nirph is hafmamnelidis; sixth generation, return migrant: a, pupa, denuded, showing
arrangement of pores: b, imago; c, antenna-much enlarged (original).
41mm TPhe antenna are also proportionally shorter, with the third
joint divided by twenty to thirty annulations. They are dark pur-
plish brown, the prothorax paler, and the eyes and thoracic lobes
black, the legs yellowish brown.





FIG. ll.-Hormniaphis himamnelidis: sexual generation: a, young larva; b, male; c, female-much
enlarged (original ).
Seventh, or sexual generation. (Fig. 11.) Female, first stage.-
The young larvae of this generation are oval, with the median line
slightly and the dorso-lateral line deeply impressed, and measure


0.2 to 0.4"'m in length. These, as well as the three following stages,
are of a 1)rown or purplish-brown color, the eyes deep purplish, and
the antennae and legs pale dusky. All are covered with a delicate,
pruinous pubescence, intermixed with a short, glistening and hair-
like secretion which gives to them a moldy or bluish appearance, all
of which in the two following stages becomes gradually so dense as to
cover the entire insect. There are also, as in former generations, two
medio-dorsal and a marginal row of short, transparent, and iridescent
waxy rods, issuing from short secretary tubercles. In this stage
there are about twelve tubercles along the front edge of the head, two
or three each side on the thoracic segments, one each side on the
abdominal segments, and two at the end of the body. There are also
two tubercles about the middle of the head, two medio-dorsal groups
of two pores each on the thoracic segments, and two median tubercles
on the abdominal segments. Antenna and legs are stout and rather
long, with two small bristles on the front of the head, a long bristle at
the apex of the second antennal joint, and three short and spine-like
bristles at the tip of the last; digitules and bristles of tibie ahd tarsi
as in previous generations. The rostrum is stout, highly developed,
and reaches to the abdomen.
In favorable years these larvae become frequently so numerous as
to cover the entire underside of some of the leaves of the witch-hazel,
in consequence of which numerous predatory insects, such as larve
of Syrphid flies, Chrysopids, Coccinellids, and various mites make
their appearance and commence their work of destruction, so that
within a few days they may be found with great difficulty.
Female, secenthl generation, second to fourth stage.-In the follow-
ing three stages they resemble each other closely, except that they
gradually grow larger, become more convex and more pyriformin in
shape, and that the antenna and legs grow longer and stouter. All
are dark purplish, and densely covered with hair-like secretion. The
secretary tubercles increase gradually in numbers and prominence,
whereby the segmentation of the body is strongly brought out. In
the fourth stage they measure about 11"'m in length. The legs and
antenna are considerably longer and stouter than in the other stages,
though otherwise very similar, and the rostrum shorter, reaching only
between the anterior and median coxie. There are now two large groups
of secretary tubercles at the front of the head; a group of 20 to 24
each side of the prothorax, 17 to 20 each side of the mesothorax, 11 to
16 or more each side of the metathorax, 8 to 10 each side of the first
three segments of the abdomen, 3 to 6 each side of the other four seg-
ments, and about six on the terminal one. There are also two median
groups of 7 to 10 tubercles on the head between the eyes; two medio-
dorsal groups of 10 to 15 on each of the thoracic segments; 8 to 10
or more on the four anterior segments of the abdomen, and from three
to six on the other three segments.


Serenth generation, imature Jfemnale.-After having cast the last skin
they measure but slightly over 1""11 in length. They are broadly pyri-
form, highly convex above and quite flat beneath, surrounded with a
rather broad and deep dorso-lateral depression. They are polished,
of a deep black or purplish black color, and without a trace ot secre-
tion of any kind, and, when seen on the leaves, remind one strongly
of certain small Coccinellids, such as Pentilia, and also of some of the
Oribatid mites. All of the secretary tubercles have now completely
disappeared. The head is arcuate in front and bears two to four
small hairs. Eyes small, each composed of three ocelli. The rostrum
is highly developed and reaches almost to the median coxae. The
antenna are much longer than in the last larva stage, and about as
long as the posterior tibie and tarsi combined; the two basal joints,
as usual, are stoutest, shortest, obconic, subequal in length, and pro-
vided with a short bristle near the inner apical angle; the third joint
is very long and slender, of uniform diameter, rather densely and
sharply serrated or annulated, provided with the usual sensorial
thumb and two or three short hairs at the apex. The legs are long
and stout, and bear the usual bristles on the tibim and tarsi; the
digituls are well developed and capitate, the lower pair being much
shorter and bulit slightly longer than the claws. The posterior tibia
are stouter than the others, and are provided with a considerable
number of sensorial pores or tubercles. The tail is small, trans-
versely oval or knob-like, and bears six bristles; the terminal segment
is 1)ilobed, each lobe bearing three to four bristles. Each female con-
tains from five to ten eggs, which, shortly after copulation, are deposited
around the base of the leaf buds for next year's brood.
SevenW/h g minale and its general similarity to female larvae I failed to ascertain
through how many transformations it passes, though they are evi-
dently the same as those of the female. The mature male measures
0.4 to 0.6;"'" in length, and about one-half or less the size of the
female. It is of the same black or purplish-black color and of an
elongated pyriform shape, being broadest about the middle of the
thorax and gradually tapering toward the end of the body; the front
of the lead is rounded and bears two small hairs. Surface of body
densely reticulated. Secretory tubercles are wanting. The antennae
are considerably longer and more slender than in the female; the two
basal joints are subequal in length; the first joint is stoutest and
about as long as broad, stoutest near the truncated apex; the second
joint is clavate and more elongated; both bear bristles at the inner
side near the apex. The third joint is very long, slender, and of equal
diameter up to the terminal thumb, slightly curved inward, profusely
serrate or scaly and bears along its external edge from ten to fifteen
or more minute an(d colorless sensorial thumbs and three small hairs
at the apex. Eyes composed of three ocelli. The rostrum is highly


developed and reaches beyond the median coxw. The legs aire long
and more slender than in the female. The tail is i all aifid knob-
like, and bears two small bristles; the last segment is rounded and
provided with four small bristles. The mature male is extremely
active and restless and is continually running about in search of
mature females. Copulation lasts but a short time.


Harmamelistes spin osus Shimer, Trans. Amer. Ent. Soc., vol. 1, p. 284,1867.
Hormaphis spinosus, Bull. U. S. Geol. Geog. Surv. Terr., Vol. V, No. 1,
p. 14, 1879.
Hormnaphis papyyrace(c Oestlund, Geol. and Nat. Hist. Surv. of Minn.
Bull. 4, Synopsis of Aphide of Minn., p. 13,1887.
The life history of the second species of gall-making Aphids, inhab-
iting both the witch-hazel and birch, is as remarkable and interesting
as that of Hormaphis hiinumelidis. Its earlier generations, as in the
former species, subsist upon the witch-hazel, but instead of infesting
the leaves select the young and dormant flower buds for their future
operations, which gradually are changed into conspicuous, spiny galls,
the architects of which, at the proper time, forsake also their old
home and migrate to the birches to consign to them their progeny in
order to complete the cycle of existence of the species, but, unlike
1. hamiamelidis, which completes its cycle within the space of one
year, this species hibernates on the birch, on which, during the fol-
lowing spring, it produces two additional generations, the second one
of which returns during June to the witch-hazel for the purpose of
producing the sexed generation. These return migranits appear just
about the time that the spring migrants of H. hamamundlis leave
their galls, so that during this cross migration both species mavy
frequently be found simultaneously upon both plants, which occur-
rence during my earlier olb)servations caused considerab )le confusion
and speculation whether these two forms were only variations of one
or whether there were really two dist inct species. Continued stu dies,
however, have clearly demonstrated that these two forms, notwith-
standing their great similarity in venation and general appearance,
are good species, belonging to two distinct genera.
The genus IHamanmelistes was described by Dr. H. Shimer, of Mount
Carmel, Ill., in the Transactions of* the American Entomological
Society, vol. 1, page 284, 1867, to include two gall making species
found on the witch-hazel, without, however, being aware that the
first one of these two species, to which he gave the name of Hama-
melistes cornu, had previously been described by Dr. A. Fitch under
the name of Byrsocrypta hamamelidis, for which subsequently Baron
Osten Sacken erected the genus Hormaphis. Since, however, the
antennal characters of spinosus are markedly different from those of


hamamelidis, the generic jnamte o Hamnamelistes will have to be
retained for this species.
In 1879 it was again partly described by Prof. C. V. Riley in the
Bulletin N1o. 1 of Volume V of the U. S. Geol. and Geog. Survey,
p. 14, who erroneously referred it to Hormaphis.
Mr. 0. W. Oestlund, wile studying the Aphides of Minnesota,
described an insect, which he found to corrugate the leaves of birches,
in Bulletin 4, of the Geological and Natural History Survey of Minne-
sota, page 17, 1887, under the name of Hormaphis papyracea', not
being aware that lihe had discovered the return migrant of Hamame-
listes sp)inosvus. TIie complex history of these two remarkable species
has remained a sealed book up) to the present time, when, at last, it
has been solved.
My own acquaintance with thle birch-inhabiting form of this species
dates back to May, 1887, wheii I discovered the younger stages of it
on the young leaves of a small birch at Richfield Springs, N. Y., but
failed, on account of the immature state of the insects, to recognize its
generic position. It was again found by me in June, 1893, on leaves
of young birches at Charlton Heights, Md., in various stages of devel-
opment, including the migrant, but considered it to be a new species
of Hornamplis, which I later found to have been described by Mr.
Oestlund. My failure to recognize it at that time as the return
migrant of .spin'o.s.s was in at great measure due to the fact that at the
date of finding these migrants on thle birches I observed also young
galls of s)pinosus on tlie witch-hazels.
The geographical distribution of this species depends in a great
measure on thle presence of both plants in thlie same locality. In
favorable seasons it may become so numerous as to cause great injury
to the foliage of birches, inducing the leaves to fall prematurely.
winter eg( (Fig. 12).--Thlie winter eggs of this species, unlike
those of Horimpjlis h1minamolidis and the majority of other Aphids,
are deposited from about the middle of June to early in July, instead
of during the fall of the year, and hatched by the end of May or
early in June thle following year, remaining dormant almost a whole
year, whereas in the other species it takes only about one-half of that
time. These eggs are commonly deposited between or near the
crotches formed by the twigs and petioles of the flower buds, the
scars left by previous flowers or seed capsules, and in crevices of the
bark, or similar sheltered positions. That the instinctof the migrant
is rather defective in selecting the proper shrubs of witch-hazel
for the continuance of its race has been demonstrated by the fact
that it will migrate ind(liscriminately to both the bearing and imma-
ture plants, on account of which the young stem-mother, hatching
from eggs deposited on immature plants, is doomed to perish through
absence of flower buds on which to settle. I have repeatedly found
large numbers of the sexes and their winter eggs on immature


plants, though never a gall of this species on them, whereas the other
species, inhal)itiig the leaves, thrives equally well on the simiallest
plants but a few inches high, as well as upon fully grown trees, and
is therefore the more common and more numerous of the two.
The eggs of this species are rather peculiar, quite flat, about three
times as long as broad, and about 0.21"1m long; they are regularly oval,
and covered with a glistening, hair-like secretion, applied to them
when deposited, from the hair-like secretion on the abdomen of the
female, which gives to them a hoary appearance, corresponding quite
well with the pubescence of the twigs, and rendering then very dif-
ficult of detection. They are at first of a pale yellowish color, but
change gradually to a dark gray or blackish color, corresponding
more or less closely with the color of the bark, which makes it still
more difficult to detect them.
They are tightly glued to the \\
twigs, and are so extremely
delicate that it is almost im-
possible to remove them with-
out breaking.
The gall (Fig. 113).-At the
time of hatching of the eggs'.
of this species, which takes .,
place from the middle of May
till early in June, the young
flower buds measure about 1
to 1.411111 in diameter. They ,J\
are globular, with three shal- \
low longitudinal grooves, sit- '
uated on a short, rather stout,
and succulent petiole, which a
is surrounded with four or FI(,. 12.-Hamamelistes spinosus: a, winter egg, much
more small and lanceolated magnified: b. twig of witch-hazel with young flower
nore buds and eggs in position-natural size (original).
leaflets. They are of a yel-
lowish-green color and densely pubescent or hairy. The young stem-
mother, after hatching, readily finds the buds and selects almost
invariably that side of it directed toward the twig and settles down
near the base in one of the grooves of the bud. The ensuing irrita-
tion, caused by the sucking of-the insect, and probl)al)ly also through
injection of an irritating fluid, checks the longitudinal growth of the
petiole, l)ut hastens that of th,, bud, especially that side of it opposite
the insect, which at once commences to lengthen, to broaden, and to
curve over toward the gall-maker, and to acquire a beautiful rosy color.
The formation of the young gall proceeds rapidly, so that within a few
days the insect is completely inclosed, leaving but a transverse scar
and small opening where tlhe insect had settled, by which time the
original structure and component parts of the buds have become com-


pletely fused. Fie newly for(medl gall i.s also globular and hut slightly
larger than the original bud. lThey grow now rapidly, so that by
about the middle of June the oldest or earliest formed galls are about
half grown, have lost their beautiful rosy tiut, and are now of the
same pale, dingy green color of the buds. They are globular; the
opening or mouth is closed and indicated by a fine whitish pubescense;
while the leaflets surrounding the petiole have dropped. The surface
of the gall has become densely tuberculate and in addition is covered
with a greenish-white pubescence, while the tubercles are covered with



,,., .
S'Ile / a

Il' 11 /1.

'* I *". ,i t i ,' I '"',,,s"iI' "
4. :'. "1 *'* ,,

Fi<. l.- ma tts spiosus: (i. twig of witb-hazel with young galls, natural size; b.
young gall-much magnified original).
the peculiar brown and branching papilla' which are noticed on the
buds. They are fully grown by the end of .June or early in July, and
have acquired the characteristic shape.
The mature galls (Fig. 1-1) vary more or less in shape and size.
Their shape varies from globular to ellipsoidal and their size from 10
to 30r1111 in length by 10 to 121111"" in diameter. Their surface, when
fully grown, is now covered with long and stout more or less curved
spines or teeth, which frequently may attain a length of 8n"' or more,
though ,s the galls grow older and become dry these spines become

shorter anid blunter. The whole aspect of these galls when fresh is
that of a miniature seed capsule of the common Jamestown weed
(Dahtura stramonwiiun). They are of about the same green color of
the leaves and studded with reddish brown papillm. The orifice or
mouth, at the base of the gall, is circular and 1 to 2'"", in diameter,
with its external prolongation more or less decidedly funnel-shaped,
terminating in a rounded or bulging rim, to allow the departing
migrants space to adjust theirwings for flight. The inner wall of the
gall is smooth and coated with a delicate layer of a white secretion,
to prevent the watery fluids, or honeydew, expelled by the insects from
adhering to the surface, as a preservative against premature decay or
the during up of the tissues of the .'-alls. After attaining their full

Fid. 14.-Hamamelistes spinosus: a, mature gall; b, section of gall-natural size (original).

growth, they renaiai fresh and succulent for a long time, so as to
enable the latest additions to their inhabitants to acquire maturity.
The majority of these galls become dry and brown by the end of suim-
mer, though occasionally fresh and( green ones, containing the insects
in various stages of development, may even be found as late as the
end of November.
Stetm-in otflr; first stage.-The young stem-mother, after hatching,
is extremely small and measures only about 0.2 mm in length. She is
broadly oval and of a dark purplish-brown color; the eyes, antenna,
and legs are blackish. The head is broadly rounded in front and
bears two small bristles. There are three short and stout secretary
tubercles each side of the p)rothorax, arranged in a triangle-two each


side (on the other thoracic segments; one each side of abdominal seg-
ments one to seven and two, bearing two small bristles, on the last
segment. There is also a semicircular row of four similar tubercles
near the inner edge of the eyes and a transverse row of four between
the eyes; two outward-curved medio-dorsal rows of four tubercles in
each row on the prothorax; a transverse row of four tubercles on the
mieso- and inetathorax; two median tubercles on the first three abdomini-
nal segments and one on segments four to seven. The antennae are
short, four-jointed, and inserted on the underside of the head. The
two basal joints are short, stout, and subequal in length; the third is
longest and slightly stoutest at the apex; the fourth is somewhat
shorter, clavate, and terminates in a short, blunt spur; both are
slightly annulated or serrate and bear a slender cylindrical thumb
near the apex. Iegs stout; the (posterior til)ia bear near the end two

___ . 4

6 a
Fl;. 15.-Ihunnm1clistes pi)jnmsus: u, mature stem-mother, dorsal viow; b, ventral viuw;
r, antenna-much magnified i original).

long, backward-curved bristles, and the tarsi a similar one oni their
external edge. The digitules of all the tarsi are long and capitate,
the lower pair being much I hie finest. The rostrum is long and taper-
ing and reaches beyond the posterior eoxue.
In the following two stages the larvae have lost all of the secretary
tubercles, which are to some extent replaced by hairs. In other
respects they are very similar to the first stage.
Adult stem-moth-i/hr; fourth staye (Fig. 15).-The full-grown steinm-
mother is almost globular or broadly pyriformn, about 2""" long, and of
a dark purplish-brown color, covered with a mealy secretion; antenna,
legs, and rostrum blackish. Eyes small and composed of three ocelli.
lThere are apparently two bristles on the front of the head, two
eachli side of the thoracic, and one each side of the abdominal segments.
The tail is small, broad, knob)-like, and bears two bristles; the last
segment is broadly bilobed, and each lobe is furnished with about


eight bristles. Antennae short, stout, and four-jointed; the two basal
joints are shortest and stoutest, each bearing a bristle near the apex;
joints 3 and 4 are longer and subequal in length, the third is clavate,
and the fourth elongated oval; each bears a small thumb near the apex,
and the fourth three small capitate hairs and a small spine at the tip.
The rostrum is stout and reaches beyond the anterior coxae. Legs
short and stout; the digitules of the claws apparently wanting.
That the stemi-mother of this species is extremely prolific was proved
by the fact that one mature gall, found July 9, contained, besides the
6tem-mother, 220 of her progeny, in various stages of development,
froni the recently deposited larve to the winged migrants, the old
mother being at the same time still very plump and almost globular,
containing yet a large number of embryos, which, after all have been
deposited, may increase her descendants to about 300. The galls are
sometimes so completely crowded with the insects as to allow but little
room for them to move about.
Second generation, first stage.-The young larva of this generation
are brownish-red or grayish-green and gradually develop into the
migratory form. They measure between 0.4 and 0.8"1"1 in length, and
are about twice as long as broad, with almost parallel sides. The
head is nearly straight or broadly rounded in front, and bears a
rounded, fleshy tubercle. The abdomen is about one-half the length
of the body; its segmentation very distinct. The head and prothorax
are confluent and as long as the combined meso- and mietathorax.
The rostrum is stout and reaches almost to the hind coxwe. Antenne
four-jointed, curved inward, short and stout; the two basal joints
are stout and short, the third and fourth are subequal in length;
the third is clavate and the fourth slightly tapering; each bears a
cylindrical and movable thumb. Legs stout and rather long; there is
a rather long bristle near the apex of the femora; two, externally, on
the tibie and one or two on the tarsi; digitules long, slender, and
apparently simple; those of the claw are wanting. There are also
four or more bristles along the front of the head, two each side of the
thoracic, one each side of the abdominal segments, and four at the
end of the body.
Second generation, second stage.-In this stage they are still very
similar to the young larva, though they are much stouter and about
1.2'1"m in length. The antenna are now distinctly five-jointed, rather
stout, and still more curved inward; the two b)asal joints, as usual,
are short, the first stoutest; the other three grow gradually some-
what longer, the fifth being somewhat the longest and thinnest; joints
two and four are clavate, the third cylindrical, and the last one con-
ical, its tip rounded; the last two joints, as usual, bear each a small
thumb. The rostrum reaches to the median coxe.
Scoid generation, th ird stage.-In this stage they are still larger
anmd stouter, and measure about 1.4 to 1.6"1111 in length. The future


wing pads are now indicated by a rounded swelling each side of the
pro- and mesothorax. The antennae are about twice as long as before,
and reach, if laid backward, to the median coxwe. Joint three is
longest, the two last ones somewhat shorter and subequal in length;
joints one, three, and four are cylindrical; the second, which is
slightly the shortest, is stoutest at the apex; the fifth is curved and
u.apering; the last two bear the usual thumb. In other respects they
are very much like before.
Second generation, fourth or pupa stage.-In this stage they are
still larger and stouter than before, and measure 2.4 to 2.6m1"1 in
length and have now fully developed wing pads. They are reddish-
brown tx) purplish-brown, the disc of the thorax more yellowish; eyes
brown, the antennae, legs, and wing pads whitish, the external mar-
gin of the latter blackish. The front of the head is now concave and
the frontal tubercle minute. The antennae are again much longer
than before, or alnmot twice as long, with the division between joints
three and five almost obliterated. The eyes are large and well

Fit;. It;. -Ht muawin elisti. s.pinsu.: Spring migrant-much enlarged (.original).

Second generation, migrant or fifli saluge (Fig. 16).-Early in
July, or about a month and a half after hatching of the stem-mother,
the earliest migrants are fully developed and commence leaving the
galls and continue to issue till'late in the fall. Having adjusted
themselves, they start on their migratorial trip, during which they
mlay frequently alight on the leaves of various plants, not alone for
rest, but evidently for the purpose of determining the nature of the
plant on which they may happen to be, though they will rarely deposit
any larvae until their unerring instinct finds the birches, the only
plant suitable for the welfare of their progeny. Each of these
migrants contains from thirty to forty or more larva, or only about
one-seventh as many as the stem-mother. These migrants are rather
larger than those of Horinaphis hamnamehdis and measure between
1.8 and 2.4mm in length, with an expanse of the wings of 4 to 6mm.
They are stoutly built and of a dark, purplish-brown color; the head,
eyes, antenna a dorso-lateral spot on the prothorax, thoracic lobes
and sternal plate, black, and the legs dusky; apex of abdomen more


or less distinctly reddish; the wings are clear or faintly brownish, with
the costal cell and stigma dusky and the veins blackish. They are
slightly covered with a white and powdery secretion and, when not
rubbed, have also two small tufts of a dense and white secretion on
the scutellum, a similar tuft or patch each side on the thorax, and
some fibers or flakes of secretion on the abdomen. Antenne five-
jointed, reaching only to the base of the wings; the two basal joints
are short, with joint two almost globular; the third joint is longest,
and as long as the remaining two combined; the last two are subequal
in length, all three are densely and deeply annulated. There are
between twenty-seven and thirty-two annulations on the third joint,
twelve to fourteen on the fourth, and eleven to thirteen on the fifth
joint. The head is broader than long and distinctly conical in front;
eyes large. The legs are rather short and slender, the digitules highly
developed. Tail small, transversely oval and knob-like, tuberculated,
and hairy; the last segment is bilobed, and each of its lobes furnished
with numerous, rather long hairs. The wings are large and broad
and are carried flat on the back when at rest; the stigma is broadly
lanceolate and somewhat broadest at the base of the stigmal vein.
The venation is similar to that of Hormaphis ham the second discoidal vein joins the first much nearer its base than in
the other species. The first discoidal of the posterior wings is rarely
entire, and is usually represented by a small stump; sometimes it is
Tih ird, or Coccidiform, generation.-After having fully matured the
winged form leaves the witch-hazel galls and migrates to the leaves
of birches to deposit their larve, which after a short time of feeding
move to the twigs and branches and settle down close to a bud for
their future transformation and for hibernation. Their growth
appears to be very slow, and many of them perish before the approach
of spring, so that usually but very few adult females will be found.
Third generation, first stage (Fig. 17).-The young lir\va- of the
migrant from witch-hazel are very peculiar, and resemble more closely,
when seen on the twigs, the larve of a Lecaniid than those of an Aphid.
They are about O.411kn in length, about twice as long as broad, oblong-
ovate, and rather flat above. A slightly elevated rounded carina runs
from the head to the end of the body, which is traversed by fine
impressed lines, indicating the Adivisions of the body but failing to
reach the lateral margin. There is also a rather deep fovea each side
of the carina on the prothorax and a puncture each side of the carina
on the other two segments of the thorax. The abdomen in compari-
son with the rest of the body is very small, or only about one-third or
less of its length. The dorsum is densely granulated and more or less
polished. The lateral edges are studded with about 30, and the front
of the head with 16 to 18, short, truncated, and cylindrical secretary
3504-No. 9-01- 3


tubercles, from each of which issues a transparent and colorless
straight or slightly curved cylindrical waxy rod.
When first deposited these larve are of a reddish-brown color, the
antenna and legs paler, and the eyes dark purplish, which soon changes,
however, excepting the under side of the body, to a beautiful, brilliant
dark metallic blue or green, while others change to bluish-green, pur-
plish, or to a brassy or coppery reflection. The antennae are short,
four-jointed, and inserted on the under side of the head. The first
joint is shortest, stoutest, and slightly conical; joint two is somewhat
longer and slightly clavate; the third is longest, cylindrical and about
one-third longer than the second, while the last is a little shorter than
the third and bears the usual sensorial thumb near the apex, the tip
being surrounded with a few short hairs. The rostrum is stout and
reaches beyond the median coxae.
b Legs stout; the tarsal digitules are
long, capitate and curved; those of
the claws are much finer, straight,
S and only about half as long as the
Others. There are also two or three
S/ c long and stout, backward curved
\bristles near the end of the hind
\ tibiae, and two similar ones on the
hind tarsi.
e Th i rd gene ration,second stage. -
S/ \The larvae in this stage are about
,\ \ 0.6"1"' in length, broadly oval and
S_ still rather flat; being but slightly
d convex on thile thoracic segments
Fil. 17.-Hanmamnelistesspinosus: a, hibernating and along the middle of the abdo-
larva, third generation: f, antenna; c, ros- men; the sutures dividing the
trum; d, tarsus; e, lateral tubercles and waxy
rods-much enlarged (original. various segments are quite plain,
though they do not reach to the
lateral margin. The surface of the body is now finely rugose and its
lateral margin surrounded by a very short fringe of waxy secretion,
issuing from closely set secretary tubercles. The antennae are now
much shorter than before and only three-jointed; the two basal joints
are short and subequal in length, while the third is about as long as
the two basal joints together, slightly tapering and truncate at the
tip. The rostrum has become shorter and reaches only to the median
coxwe. The legs are also shorter, while the anterior and median legs
have lost their tarsi, which sometimes are indicated by a minute, knob-
like swelling; the posterior pair of tarsi are still present, though rather
short, irregular in outline and have lost the claws; the digitules are
still present, though rather short and fine. The color of the insect is
now of a dull black or dark brown.
Third generation, third stage.-In this stage they look very much


like before, except that they are much broader and about 0.8""11 in
length; the surface of the body is now densely and finely rugose, and
the sutures between the segments have become deep and broad; there
is also a depressed subdorsal line around the body; the tail is broad,
semicircular, more distinct than before, and furnished with 4 to 6
hairs. The antenna are still three-jointed, the second joint being
much the longest and cylindrical and the third joint minute or rudi-
mnentary. They are dark brown or black and greasy looking.
Thirdl generation; ad female of this generation is broadly oval and measures 1.2 to 1.4m1 in
length and 1 to 1.2m1" in diameter. After casting the last skin they
are deep black, convex, and densely
and coarsely rugose, with three rather .
prominent, short, and rounded I rans- .
verse ridges about the middle of the -B'
body, and irregular rows of pits and
depressions each side of the median -B
line. The edge of the body is closely
lined with about 120 short, secretary
tubercles and about 14- similar ones
along the edge of the tail, producing a a
continuous, but very narrow, waxy d
fringe around the body. The dorsal <
surface is at first bare, but soon be- e
comes covered with a whitish, powdery / j-
secretion, which gives to the insect a
moldy appearance; this changes grad- ...
ually into scattered, delicate, waxy ..
flakes or scales, which, toward the ap- ./
proach of spring, form a solid and
continuous waxy covering, most dense c
or solid along the sides and the end of F(;. 18.-Hamamelistesspinosus: a,adult
female, third generation, dorsal view;
the body, giving them a dark silvery- b, lateral view; c, ventral view; d, an-
gray appearance, on account of which tenna; e, f, f, legs-much enlarged
they assume a remarkable resem-
blance to certain species of the Lecaniid genus CUe,)ochiton. Advanc-
ing to maternity, the ventral side of the body becomes very much
inflated and assumes a box-like appearance, as in some Aleurodids,
and is covered with a powdery secretion. The antenna are now very
small and rudimentary and apparently but two jointed, though there
may be three,,which, however, could not be ascertained with certainty
on account of the very dark color and the coarse rugosity of the body.
The legs are as in the previous stage, except that the hind tarsi are
only about half as long as before.
Pseuido-galls, or corrugations (Fig. 19).-About the middle 'of
April, or just about the time of bursting of the leaf-buds of the


birches, the coccidiform, or hibernating females, have attained their
full development and begin at once their duty of reproduction. The
young larvae soon after having been deposited are directed by their
inherited Instinct, to move at once to the young and tender leaflets
which are just bursting forth, and settle on the under side in the folds
or plications between the transverse veins. The continuous irritation
produced by the sucking of the insects causes the edges of the young
leaves to curve down, while at the same time the upper surface of the
leaves between the veins commences to bulge out and gradually forms

Fi(. 19.--a}lrisenlistes Pseudo-galls. or corrugation,,, on leaves of birch--natural size
Original '.

rounded ridges, or corrugations, while t e folds on the under side
gradually close up. The thus formed pseudo-galls, offer ample room
for the gall-mnakers and their progeny. These corrugations or folds
acquire a reddish-brown shade which soon changes to a beautiful red-
dish or crimson color. The growth o(f the young insect is rapid, keeps
pace with the growth of the infested leaves and reaches full develop-
minent by the end of April or early in May, or about twenty days from
the time they were born and commence at once to reproduce their
kind, which frequently become so numerous as to fill these pocket-
like folds to their utmost capacity. In favorable years the insects


are apt to become extremely numerous, so as to injure even large
trees very seriously, causing the infested leaves to turn gradually
brown and to drop after most of the insects have left. This injury to
the foliage of badly infested trees or shrubs, as a rule, is very severe
on the branches, many of which gradually dry up and die, which
injury, if continued for a number of years, will kill the tree-. The
development of the second generation of the gall-inhabiting insects,
which eventually become winged, is also rapid, to enable them to
attain full development before the leaves commence to drop and
to be ready for return emigration to the witch-hazel early in June, to
give birth to the final or sexed generation, to complete the cycle of
existence of the species. This
is the generation described by g_ .
Mr. 0. W. Oestlund in his
"Synopsis of Aphidw of Min-
nesota," under the name of
Itorrmaphis papyracea,.
Fourth J aeration, first /, "D$ \
stage. (Fig. 20).-The general / f
appearance of the leaf-corru- s .
gating generation has so corn- e ....
pletely changed as to bear no
resemblance whatever to the -_
previous coccidiform genera- N 'D[
tion; so much so as to render -S
it impossible to detect their [ .. J
affinity or their close relation- N
ship except by continued and
close observation; which I
have been so fortunate as to a.
trace without the shadow of a FIG 20.-Hamamelistes spinosus: a, Young larva,
fourth genwrati,,. dorsal view; b, ventral view;
doubt. c, antenna: d, eye: e, adult female. dorsal view:; f,
The young larv-ie first ventral view; g, antenna-much enlargt-u (origi-
The young ]alrVw wvheln first hal).
deposited arc of an orange
color, but soon change to yellowish-brown; marked with two bri oad
and faintly dusky stripes on the head, which extend to the prothorax.
The eyes are purplish, with three colorless ocelli. Antenna and legs
dusky. They are elongate-oval, slightly convex, distinctly segmented,
and 0.3 to 0.5mm in length. The head is broader than long and semni-
circular in front, where it bears four short bristles arising from small
tubercles; two similar bristles are each side of the thoracic, one each
side of the abdominal segments, and four along the edge of the broad
and semicircular tail. There appears to be also a transverse row of
four short bristles on the thoracic segments and two, medio-dorsally,
on the al)bdominal segments. The antenna are four-jointed; the two
basal joints short and subequal in length; the two last joints long


and also subequal in length; joints one to three are cylindrical
or slightly stoutest at the apex; the fourth being elongated oval.
The third and fourth are slightly annulated, each bearing a small
and movable thumb. The legs are long and stout, with the hairs and
digitules very similar to those of previous generations. The rostrum
is stout and reaches to the posterior coxae.
Fourth generation: second stage.-In this stage they measure
between 0.6 to (.!,", in length and are broadly ovoid, broadest across
the thorax and gently tapering toward the end of the body. They
are of a reddish color, marked with two large and triangular, dusky
or black spots near the anterior margin of the head, two to four
small duskyspots between the eyes and a dusky, depressed subdorsal
spot each side on the prothorax. Eyes, antenna and legs black, the
rostrum dusky. The body is covered with a white and powdery
secretion, most profuse along the middle. There has now also
appeared a short and dense brush of a white and glistening secretion
each side near the end of the body. The rostrum is shorter than
before and reaches to the median coxa,; antenna four-jointed as
before: the two basal joints, as usual, short, subequal in length
and slightly stoutes.t at the apex; the third joint is longest and cylin-
drical, tlhe fourth but slightly shorter and both bearing a short thumb
near the apex: there is a rather long bristle near the apex of the two
basal joints and a number of small hairs at the apex of the fourth.
The anterior and median tarsi have been lost or are represented by a
minute rounded stuimp. The hind tarsi are present, but have lost the
claws; bristles and digitules of hind tibia? and tarsi are present. The
hairs of the head and body are now much longer and stouter than in
the first stage.
Four'/h ge/-ir'f/fioi: hird' s/agp.-In this stage they are almost
identical with those in the previous stage, though they) are now almost
gloiular, 1'l"" in length and of a dark-greenish or brownish-green
color, marked with two large dusky spots on the head, reaching beyond
the eyes. The powdery secretion forms now a distinct white line
along the middle of the back. The rostrum has grown still shorter
than before; the tail is broad, provided with six hairs and densely
covered with rows of minute and(l sharp spines.
Fourtli feiiritin : adidt feniale, or fourth stage.-The adult female
of this generation is very convex, almost globular, 1.2 to 1.6"n' long
and ] to 1.2""'1 in diameter. They are at first dark brownish-red,
changing gradually to dark yellowish-green, and finally to a purplish
color; the front of the head, two small dots on the prothorax, a band
at base of the tail, tip of tail and of the two lobes of the last segment,
eyes, antenna&, legs, and rostrumn, all black. They are slightly dusted
with powdery secretion as before, and bear also a short brush of
secretion along both sides of the abdomen. The segmentation of the
body is quite distinct; there is also a rather deep dorso-lateral groove


or furrow around the entire body, which, with the lateral margin,
forms a prominent, rounded ridge. The antenna are identical with
those of the previous stage, except that they are somewhat longer.
The anterior and middle tarsi are either wanting or are sometimes
represented by a minute, squarish stump, which occasionally bears
at its external angle two rather stout, outward-curved booklets, evi-
dently the representatives of claws, while the hind tarsi, in the major-
ity of cases, are again quite normal; some specimens have one or two
perfect claws, indications of claws, or none whatever; the tarsal digi-
tules of the posterior legs may be well developed, rudimentary, or
wanting. The mature insect may, however, be always recognized by

\ "7.-:-UT_ ,. ---4 -- _.. f------.-4-------

d c e
FIG. 21.-Hamamelistes spinosus: a, young larva, first stage, fifth generation; b, larva, second
stage: c, prepupa, third stage: d, pupa; c, return migrant; f, antenna-much enlarged

the formation of the last abdoinial segment aid the sliap)e of the tail;
in the immature specimens the tail is short, very broad, being either
broadly arcuate or with an obtuse angle medially, while the last
abdominal segment is semicircular and entire. In the adult female,
however, the tail is small, transversely oval, knob-like, and bears two
bristles, the last segment beiig stronjigly bilobed, each lobe bearing
ten or more long hairs. The rostrum is short and reaches but slightly
beyond the anterior coxa'. The hairs of the head and body are simi-
lar to those in previous stages, except that they are longer and stlouter.
Fiflt or miigra(tory generation; firs/ staye (Fig. 21).-Early in
May the leaf-corrugating females or fourth generation of the series
are fully matured and coinmienee their reproductive functions. The


young larvae of this generation are at first pale yellowish, but as they
grow inii size become much darker. The head isdusky; antennae, legs,
and rostrum darker, and the eyes black or purplish black. They are
dusted with a mealy secretion, and soon acquire a short brush of white
secretion along each side of the abdomen. They are about O.61"n in
length, much elongated, and almost three times as long as broad, with
the sides nearly parallel. The front of the head is almost straight
and l)rovided at the lniddle within a prominent, rounded tubercle. The
posterior end of the body is rounded. The antennae are four-jointed,
rather stout, and slightly curved inward; joint two is slightly the
shortest, the first stoutest; both bear a bristle near the apex; joints
three and four are longer and subequal in length; the third is
cylindrical and bears a small thumb near the apex; the last joint
is slightly curved, tapering, and faintly annulated, bearing the
usual thumb and several short, stiff bristles around the apex; they
reach about as far back as the first coxae. The rostrum is stout and
reaches beyond the median coxae. The legs are long and stout, with
the tarsi and claws highly developed. There is a rather long bristle
near the end of the femora; two hairs or bristles near the end and
one about the middle of the tibiae, those of the posterior tibiae being
much the longest; also one or two shorter ones on the tarsi. The
tarsal digitules are very long and capitate; those of the claws appear
to be wanting. The body is provided with four dorsal rows of small
tubercles, each bearing a short and stout hair. Similar tubercles, and
hairs are also present along the sides of the body and front of the head.
Fifth generation: seC 'oJM stgrje.-In this stage they resemble still
very much the young larva', though they measure now already 1111"1
in length and are of a more elongate shape. They are, as before,
covered with powdery secretion and provided with a lateral brush.
The head is almost straight and has lost the frontal tubercle; the
rostrum is shorter and reaches between the anterior and median
coxa,. The antenna' are now five-jointed, very stout and distinctly
curved inward. The two basal joints are short, each bearing a bristle
near the apex; the third and fourth are nearly subequal, with the
third somewhat the longest; the fifth is longest of all, curved and
tapering, bearing a number of spine-like hairs around the apex. The
last two joints bear the usual thumbs. All the tarsi, claws, and digi-
tules are present. The hairs of the body and head are now much
longer and stouter than in the first stage.
Fifth generation; third stage.-In this stage they resemble still those
of the second, though they are larger and measure about 1.2 to 1.4mm
in length. The future wing-pads are now indicated by rounded swell-
ings at the sides of the mnieso- and metathoracic segments. Tarsi and
claws present, as before. The antennae are now about one-fourth
longer than in the second stage, the third and fourth joints being sub-
equal and longer than the others; in other respects they are as before.
Fifth generation; fourth or pupa stage.-The fully developed pupae

vary to some extent, in size, measuring from 1 to 1.6I"" in length. They
are of a reddish or purplish-red color, with the prothorax somewhat
the darkest, the head and rest of the thorax palest, the shoulders
whitish or yellowish. Eyes brown and the ocelli red. Antennae, legs,
wing-pads, and rostrum pale dusky; the sutures between the antennal
joints white and the external edge of the wing-pads blackish. All
are covered with a dense, straight and hair-like, white and glistening
secretion, which is most dense and brush-like along each side of the
abdomen; this secretion is apt, however, to be easily detached by the
movements of the insects within the folds. The antenna are much
longer than in the preceding stages, and if directed backward would
reach to or beyond the base of the wing-pads. The third joint is
much the longest and almost as long as the two last joints combined;
the fourth and fifth are subequal in length; the sensorial thumb of
each is minute; the third and fourth are cylindrical and the last one
slightly tapering, with the usual hairs at the apex. In other respects
they are similar to those of previous stages.
Fifth generation; migrant, or fifth stage.-The winged form or
return migrant is much smaller than those leaving the witch-hazel
galls, being only about one-half their size. Length of body, 1.6"1"1,
and expanse of wings about 5m"". They are dark reddish, the abdo-
men frequently with a purplish tinge or sometimes greenish h-brown.
Head, antennae, an oblique or triangular depression each side of
the prothorax, thoracic lobes, sternal plate, and tarsi, black; the
legs dusky. Wings faintly dusky, the subcosta and stigma dusky,
the costal cell somewhat paler; veins black. Antenna five-jointed; the
second joint is almost globular; the third is much the longest; the
other two subequal in length and together somewhat longer than
the third; all three are strongly and deeply annulated, the number of
annulations in each varying more or less; those of the third joint vary
between 20 and 30; in the fourth between 10 to 13, and in the fifth
between 14 and 15, though in some spelcimens there may be but a very
few and widely separated annulations on the last joint. The legs are
normal and the digitules of the tarsi, as well as the claws, -well devel-
oped. The head, including the eyes, is about twice as broad as long
and more or less distinctly conical in front. The tail is knob-like,
densely covered with minute spines, and bears two long and about six
smaller bristles. The last abdominal segment is deeply bilobed and
densely spinous, and bears in addition a number of bristles.
Fifth generation; (accessory, apterous female.-In the folds or cor-
rugations, in company of the winged form, are frequently found
apterous females, belonging to the fifth generation, which are des-
tined to produce an additional or intermediate migratory generation.
The economy of these apterous females and additional migratory
generations remains rather obscure.
These accessory female's are of a dirty brownish color, and densely
3504--No. 9-01- 4


covered with a short, flocculent secretion, giving them the appearance
of mealy bugs, and measure about 1.8'"'1 in length by about I1pm in
diameter. The front of the head is straight, the tail knob-like, the
last segment deeply bilobed and provided with bristles and minute
spines as in the migratory form. The antenna are also five-jointed,
though only about half as long as those of the migrant. The two
basal joints, as usual, are short and stout, each bearing a bristle; the
last, is somewhat the longest; the third and fourth slightly shorter,
subequal in length, and all three slightly annulated. In other respects
they resemble the previous stages.
Sixth, or sex'uld yenerathion.-From early in June till about the mid-
dle of the month the migratory generation, bred on the birches,
attains its full development and migrates back to the witch-hazel to
consign to it tih final or sexed generation. Large numbers of these
migrants may then frequently be seen on the under side of the leaves
of this shrub, in the
neighborhood of the
*=q0 oro- )1 ^ birches, and with
J_\ 9;-'. 7 '- them numerous lar-
D 0 /4.
W e ( \, scattered over the
e-- ..S surface of the leaves,
'particularly along the
0.-" ,,,=, "" midrib and the veins.
iy .d -: On one of the leaves
S"-I examined 61 living
/' "- and 20 dead. larvae
b c a were counted, and on
Fm;. S.-HumaiDiGnistc1s sspinosun: a, young larva, sixth or sexual another leaf 35 living
generation, dorsal view: b, denuded, showing arrangement of and a considerable
pores: c, tarsus; it. lateral tubercle and waxy rod; e. apex of
lateral tubercle-much enlarged (original). number of dead lar-
wle, which tends to in-
dicate that only about one-third, or even a smaller percentage of all the
larve, are able to reach maturity, and that even a much smaller
number of the winter eggs maysurviveand hatch the following spring.
The sexual generation develops also rather rapidly and reaches matur-
ity within two or three weeks, when, toward the ildle or end of
June, after copulation has taken place, the females forsake the
leaves and betake themselves to the twigs for the purpose of deposit-
ing their winter eggs in the immediate neighborhood of the dormant
flower buds, which, in the spring following, start to develop just at
the time that the egg, s are hatching.
Sixth generation, first stage (Fig. 22).-The young larvwe of the
sexual generation are of a very pale yellowish-white color, with the
eyes black and minute. They are about 0.5""' long, oval or slightly
broadest across the thorax. There are generally about twelve short
and stout secretary tubercles along the front of the head, two or three
in front of the eyes, and two near the posterior margin between the


eyes; there are also four medio-dorsal tubercles placed in a square,
and three to four along the lateral margin of the prothorax; two
tubercles medio-dorsally and three to four each side of the mineso- and
metathorax; one or two median ones on the three or four basal seg-
ments of the abdomen and sometimes one on the remaining segments;
there is also one dorso- and one ventro-lateral tubercle on each abdomi-
nal segment, the last segmnient bearing from four to six tubercles
along its posterior margin, from each of which issues a white and irides-
cent, truncated, and curved waxy rod. The head is transversely and
deeply concave in front of the eyes. Antenna- short and four-jointed.
The two basal joints are short, each bearing a short bristle; the
other two are longer and subequal in length; both are slightly
annulated, and both bear a small, sensorial thumb; the spur of the

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., ~d'

Fi(;. 23.-Haniamnelistes .sjinosu.s: a, male, dorsal view; b, antenna: c, female, dorsal view; d,
antenna; e, ventro-lateral secretary gland-much enlarged (original).
last joint is short and stout and bears two or three small hairs at the
apex. The rostrum is stout and reaches beyond the posterior coxT.
The legs are long and stout, with their tarsi, claws, digitules, and
bristles highly developed. Male and female larv-e are difficult to dis-
tinguish from each other.
Sixth generation, second to fourth stages.-In these stages they
reseml)le still those of the first stage, except that they grow gradually
larger, that the antennae increase in length, and that the two last
joints tend to become more or less distinctly fused, the division
between them being, as a rule, indicated by a very minute knob.
Sixth generation, mature female (Fig. 23).-The mature females
are of the same pale color as before and about I111"1 in length, they are
broadly oval and have lost all traces of the secretary tubercles, but
have acquired instead of them rather long and stout bristles, some of

1. ": .


which are slightly capitate; eight of these bristles may be observed.^
along the front of the head; two between the eyes; two medio-dorsajt,
ones on the thoracic segments and two in front of the tail; also t'vo
lateral bristles on the thoracic and one each side of the abdominal" ..
segments. There is now also a large ventro-lateral poriferous plate .:
or gland each side on the ventral side of the abdomen, covering seg-
ments 4 to 6, from which a dense mass of fine white and glisteni4 |
threads of waxy secretion issues, which curves up the sides of e
the body, so as to form a dense brush or rosette, the material of >4
which is afterwards used by the female, while in the act of oviposit- ,
ing, to cover the sticky eggs with the aid of its hind tarsi to disguise
them so as to conform with the pubescence of the twigs and buds. I
This habit resembles in this respect that of the sexual females of
Phylaphisfagi and certain other species, which have the same habits
of covering their eggs. The antenna are are four-jointed, though some-
times the fourth joint may be rudimentary or wanting; the third
joint is much the longest and about twice the length of the fourth; -'1
both are more or less distinctly or sharply serrate and both bear the ;'
usual movable thumbs. The rostrum is highly developed and reaches t
to the median cone. The legs, claws, and digitules are well devel- :
oped and similar to those of previous stages. The tail is small, knob- i
like, transversely wrinkled, beset with minute spines, and bears two .:::
bristles. They contain from one to five he ae rather large eggs, which fill
the greater part of the body. Iug
Sixth getieration, male.-The mature male is very small, or but ,
slightly larger than the young larv and only about one-third the size
of the mature female. It measures about O.4Ilnl in length, and is com.- ..
paratively very slender, being broadest across the mesothorax, taper-'
ing gradually toward the end of the body. The head is broadly
triangular, with the apex slightly concave. The eyes are prominent
and reddish-black. The rostrum is stout, highly developed, and ....M
reaches to the median coxae. Antenne slender, four-jointed, and.-.
reach when laid backward to the anterior femora. The third joint is o
much the longest and about twice the length of the fourth. Both are l
rather sharply and densely serrate. Joint 3 is cylindrical and bearsn
from two to three movable, sensorial thumbs, and the fourth joint: t
one or two at the base of the short spur and two or three small hairs
at the apex. The legs are more slender and comparatively longe"i
than those of the female; tail small and knob-like. All of the poresi
have disappeared. The hairs or bristles of the head and body are iem
in the female. The male is extremely active after attaining its full-:::
development and runs briskly about over the surface of the leavedlMi-'
On account of its smallness and general resemblance to the larva, "t
is extremely difficult to distinguish it from female larva. ''l
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