I n 7, % ~y r
U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ENTOMOLOGY-BULLETIN No. 85, Part VI.
L 0. HOWARD, Entomologist and Chief of Bureau.
PAPERS ON CEREAL AND FORAGE INSECTS.
CONTRIBUTIONS TO A KNOWLEDGE OF
CONTRIBUTIONS TO A KNOWLEDGE OF
THE CORN ROOT-APHIS.
R. A. VICKERY,
Agent and Expert.
ISSUED JULY 12, 1910.
GOVERNMENT PRINTING OFFICE.
BUREAU OF ENTOMOLOGY.
L. 0. HOWARD, Entomologist and Chief of Bureau.
C.. L. MARLATT, Assistant Entomologist and Acting Chief in Absence of Chief.
R. S. CLIFTON, Executive Assistant.
W. F. TASTET, Chief Clerk.
F. H. CHITTENDEN,in charge of truck crop and st8qred product insect investigations.
A. D. HOPKINS, in charge of forest insect investigations.
W. D. HUNTER, in charge of southern field crop insect investigations.
F. M. WEBSTER, in charge of cereal and forage insect investigations.
A. L. QUAINTANCE, in charge of deciduous fruit insect investigations.
E. F. PHILLIPS, in charge of bee culture.
D. M. ROGERS, in charge of preventing spread of moths, field work.
ROLLA P. CURRIE, in charge of editorial work.
MABEL COLCORD, librarian.
CEREAL AND FORAGE INSECT INVESTIGATIONS.
F. 31. WEBSTER, in charge.
GEO. I. REEVES, WV. J. PHILLIPS, C. N. AINSLIE, E. 0. G. KLLLY, W. W. YOTHEB, ,
J. A. HYSLOP, V. L. WILDERMUTH, R. A. VICKERY, T. H. PARKS, HERBERT
OSBORN, PHILIP LUGINBILL, agents and experts.
Introduction ------..-----..----...------..-------.---.---..--------------------- 97
Distribution ------------......---------..........---------------------------------- 98
Experimental work in the South ..........-----------...---------...---------------.. 100
Uncultivated food plants ......................-------------------..-----.--------------------.. 102
Injury to corn ................----------------..-------------------..------------------ 104
Relation of ants to the root-aphis ..----------------...------------.....---------- 105
Natural checks....--------...------..----.--------....-------------------------- 106
Preventive measures ----------- -------------------------------- -----106
Crop rotation ..............-----------------...------.....----.--------...----.----------- 106
Maintenance of soil fertility ----......-----------...........------------.....----------- 106
Early plowing, followed by frequent cultivations..-------..-----.....--..--------. 106
Injury to cotton--------..--...------.....----.-------------------------------- 108
Injury to asters .--------......-------....-----...-------------..-----------------. 109
Other cultivated food plants ..--..---------..---..--..--..-----...-------------------.. I11
Description and synonymy....-----------------.................--...------..------......--..---------- 111
The Erigeron root-aphis (A4phis middleloni Thos.)..----------......------....-.....---.----- 113
Uncultivated food plants-------------..-.........-----..---------------------.. 114
Cultivated food plants ---.....-----------..-----.....------------------------... 115
Attendant ants......--------------............--------.....---------...---------.--------- 115
Laboratory and field experiments ------....----...-----...---.---------------- 116
PLATE V. Fig. 1.-Damage to a field of corn in Indiana, in 1906, by the corn
root-aphis (Aphis maidi-radicis). Fig. 2.-Same field a year later,
showing the effect of applying barnyard manure -------.---.----- 104
FIG. 54. The corn root-aphis (Aphis maidi-radicis): Wingless, viviparous
female ........---------------------------------------......--------... 99
55. The corn root-aphis: Winged, viviparous female ........--....--.. 100
56. The corn root-aphis: Oviparous female.--------------..........---...--------- 104
57. The corn root-aphis: Wingless male -------------------.---------- 104
58. The corn root-aphis: Winged male..--------.-------...---------------.. 112
59. Map showing distribution of Aphis maidi-radicis and Aphis middletoni
in the United States--------------................--..-----.------------------ 114
U. S. D. A., B. E. Bul. 85, Part VI.
PAPERS ON CEREAL AND FORAGE INSECTS.
CONTRIBUTIONS TO A KNOWLEDGE OF THE CORN
(Aphis maidi-radicis Forbes.)
By R. A. VICKERY,
Agent and Exrpert.
The corn root-aphis (Aph.is m'auli-d"ics Forbes) is one of the
many insects infesting the corn plant in this country. It has cer-
tainly been known as anll enemy of corn for nearly a century, and per-
haps much longer. Besides corn it attacks sorghum and broom corn,
but does little damage to these plants. Within the last three years it
has attracted considerable attention as an enemy of cotton in the Car-
olinas, where it feeds on the roots of young cotton and is called the
" root louse or blue bug." Among its other recently ascertained
food plants are pumpkin, squash, strawberries, cultivated asters, and
perhaps dahlia and French artichoke.
Ever since this insect was first noted by Walsh in 1862 it has re-
ceived considerable attention from economic entomologists. Its life
history and habits in Illinois have been very thoroughly studied by
Dr. S. A. Forbes, state entomologist, and his assistants; and during
the past three years it has been studied, under the direction of Prof.
F. M. Webster, by the assistants in Cereal and Forage Insect Investi-
gations, Bureau of Entomology. These studies have been made over
a large extent of country, as follows: In the Northwestern States dur-
ing the season of 1908 by Mr. E. 0. G. Kelly; in Indiana by Mr. W.
J. Phillips; in South Carolina during the seasons of 1908 and 19019 by
Mr. G. G. Ainslie; a in Florida and eastern North Carolina, as a cot-
ton insect, by Mr. H. F. Wilson under the direction of Mr. W. D.
Hunter, during the season of 1909; and in the Piedmont section of
North Carolina by the writer, also during the season of 1909.
a These investigations were carried on by Mr. Ainslie as a part of cooperative
work by the Bureau of Entomology and the South Carolina experiment station
of the Clemson Agricultural College, and the results of his work were published
by Prof. A. F. Conradi in the twenty-second annual report of that institution,
for the year ending June 30, 1909, pages 51 to 65.
C. F. I. I., July 12, 1910.
98 PAPERS ON CEREAL AND FORAGE INSECTS.
An aphis frequently infesting the roots of Erigeron canadensis has il.
generally been considered as belonging to this species. It is included
in the latter part of this paper for this reason, but, as explained I
farther on, it now seems to be distinct from the corn root-aphis, and i
is therefore discussed under the name Aphis middletomi Thomas,
with the description of which it seems best to agree.
The illustrations of the oviparous female and wingless male of the
corn root-aphis (figs. 56 and 57) are kindly loaned for use in this
paper by Dr. S. A. Forbes, state entomologist of Illinois.
According to the letters of inquiry in the files of the Bureau of
Entomology the corn root-aphis has been seriously injurious to corn
in the following States (fig. 59): New Jersey, eastern Pennsylvania,
Maryland, Virginia, West Virginia, North Carolina, South Caro-
lina, Ohio, Indiana, Illinois, and. Oklahoma. Besides these States
it has been reported in literature as injuring corn in New York, Min-i
nesota, Iowa, Missouri, Nebraska, Kentucky, Mississippi, Louisiana,
and Colorado. In addition to the States mentioned above the root-
aphis was collected from the roots of corn at Sioux Falls, Huron, and
Aberdeen, S. Dak., by Mr. Kelly of the Bureau of Entomology, and
what is supposed to have been this species was collected from corn
roots at Sterling, Kans., by Mr. C. N. Ainslie, also of this Bureau.
Injuries to cotton have occurred in the coastal plain of the Carolinas.
An aphis supposed to be of this species has been reported to the
Bureau as injurious to cultivated asters from the following 'States:
Massachusetts, Rhode Island, Connecticut, New York, New Jersey,
Delaware, Maryland, Ohio, and Illinois. The species is apparently
distributed in the United States throughout almost the entire region
east of the Rocky Mountains wherever corn is grown.
It has been reported from Maine in a letter to the Bureau, but on
what food plant it was taken is not known. Although Mr. Kelly
searched for it in North Dakota, Montana, and Wyoming he did not
find it in those States. It has not, up to the present time, been re-
ported from New Hampshire, Vermont, Michigan, Wisconsin, Texas,
Arkansas, or southern Florida. It is probably present in Mexico,
although we have found no reference to it in any of the foreign
Although the corn root-aphis (figs. 54-58) was not described and
named until 1891, it has apparently been known to the corn growers
of this country for nearly a century and possibly much longer.
James Worth, in an article entitled "Observations on Insects" read :
before the Agricultural Society of Bucks County, Pa., July 29, 1822, j
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
and published, in the American Farmer,a mentioned "a species of
louse or aphis, that infests grounds and feeds upon the roots of
wheat, corn, young trees, etc., and do immense damage." And Thos.
W. Emory,b in writing of sedge in wheat, said:
I believe that this insect is the same as that known by the name of root
louse in corn, so frequently found in that plant, growing after clover, when
the land is early flushed, and which occasions so stinted and diseased a
growth that it rarely recovers till late in the summer, and not then if the
season is dry.c
Mr. Emory gave his address as Poplar Grove, without mentioning
the State. But although the State was not. mentioned, his writings
give the impression that he was talking about conditions in Maryland.
From these two notices it appears
that the corn root-aphis was
familiar to the people of Pennsyl-
vania and Maryland as early as
1822, because there is no other
aphis on the roots of corn common
enough to have been so generally
In Illinois the corn root-aphis
was first studied in 1862 by B. D. '77.
Walsh near Rock Island, where it
had attacked a small field of corn
and destroyed about half of it.
Walsh collected specimens from
which he reared winged females .
(fig. 55), and from the similarity Fia. 54.-The corn root-aphis (Aphis
of these to the corn leaf-aphis he ,inaidi-radicis) : Wingless, viviparous fe-
decided that they were identical, male, greatly enlarged, and antenna,
highly magnified. (From Webster.)
and in an essay published in the
Transactions of the Illinois Agricultural Society he considered the
leaf-aphis to be but an aerial form of the root-aphis. This view was
accepted by Cyrus Thomas and later writers who studied the species.
Dr. S. A. Forbes began his study of this insect in 1883, and, as
a result of his work and the work of his assistants, came to the con-
clusion that the root-aphis is a distinct species. So he described
it as such under the name of Aphis maidz-radicis.d His studies of
a American Farmer, vol. 4, p. 395, March 7, 1823.
b Idem, p. 71, May 24, 1822.
0 Webster, F. M.-Early published references to some of our injurious in-
sects. Insect Life, U. S. Dept. Agr., Washington, D. C., vol. 2, Nos. 7 and 8,
p. 264, 1890.
d Seventeenth Report of the State Entomologist of Illinois for 1889 and 1890.
Trans. Dept. Agr. Ill., Springfield, vol. 28, pp. 64-70, colored plate "B," figs.
100 PAPERS ON CEREAL AND FORAGE INSECTS.
this species have been continued till now its life history and habits'
as a corn insect in Illinois are very well understood.
Until recently it has not been so thoroughly studied in other sec-
tions of the country, especially in the Southern States, where its life
history and habits are widely different from what they are in Illinois.
Some of the results of these more recent studies which have been made
by the Bureau of Entomology are therefore presented in this paper.
EXPERIMENTAL WORK IN THE SOUTH.
The following laboratory experiments were carried on by the
writer at Salisbury, N. C., to determine the identity of the aphides
FiG. 55.-The corn root-aphis: Winged, viviparous female, greatly enlarged, and antenna
of same, highly magnified. (From Webster.)
found on the roots of corn, cotton, and various weeds. The method
used was to remove wingless females of Aphis maidi-radicis from the
roots of the various food plants and to place them either on sprout-,
ing cotton or on sprouting corn in vials. A plug of wet absorbent
cotton was placed in the bottom of the vials. The roots of the plants
would grow down into this and would keep alive and furnish
nourishment for the aphides for about a week. Cotton plants proved
the best for use in these experiments because they were not so subject
to attack by fungi as were corn plants. The vials were kept in the
dark. The aphides usually attack the leaves of the cotton in pref-
erence to the stem.
Ambrosia art nemisiifolia (bitterweed).-Experiment a: Apterous vivipara
were removed from the roots of this plant, September 18, and placed on sprout-
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
ing corn; they reproduced and the colony was kept on corn till November 30.
Many oviparous females and 2 winged males were produced by this colony.
The sexual forms appeared October 15. Experiment b: Apterous vivipara were
removed from the roots of Ambrosia and placed on sprouting cotton, September
24. The colony continued till November 16, producing oviparous females
Cheaopodium. album (lamb's-quarters).-Two vivipara and 1 oviparous
female were removed from this plant to sprouting cotton. This colony did well
till November 11, when the 2 oviparous females it contained were removed to
Diodia teres (buttonweed).-Experiment a: Female specimens were removed
from the roots of this plant to cotton. July 29; the colony did well till August
10, when it was killed by the death of the cotton plant from disease. Experi-
ment b: Wingless females were removed to corn, July 28. Young were pro-
duced and the experiment was continued till August 30. Experiment c: Seven
wingless females, which had produced young on corn in experiment b, were
removed to cotton, August 14. They produced young on the cotton and the
colony was continued till November 22, when it was discontinued. No sexual
forms were produced.
Diodia virginiana (buttonweed).-Female individuals were removed from
the roots of this plant to sprouting cotton, September 25. The colony did well
till December 4, when it was discontinued. No sexual forms were produced.
Leptochloa filiformnis.-Experiment a: Females were removed from the roots
of this plant to sprouting cotton, September 13. The colony was continued till
December 8 without producing sexual forms. Experiment b: Females were re-
moved from the roots of Leptochloa to corn. This colony continued till De-
cember 4. Oviparous females and a winged male were produced, and eggs
Comrn.-Wingless females were removed from the roots of corn in the field to
sprouting corn in a vial, June 16, and on July 15 females were removed from the
corn in this vial to sprouting cotton, where they established a colony which
was continued till August 16.
These experiments show that if the apterous females of Aphis
mdaidi-radici8s are transferred to the roots of corn or cotton from sev-
eral of their wild food plants or if they are transferred from corn to
cotton they will produce young and establish colonies. Thus it is
possible for the ants to transfer the aphides from a dying food plant
to any other one of a large range of food plants. Fortunately there
are many cultivated plants, such as clover, cowpeas, wheat, oats, and
rye, used in various systems of rotation, which this insect feeds on not
at all, or only rarely and for a short time.
Mr. G. G. Ainslie experimented in a different manner near Marion,
S. C., to determine the same points. Seeds of a number of species of
cultivated plants were planted near infested corn rows, trusting to
ants to transfer the aphides from one plant to another. These intro-
duced plants were examined June 5, with the following results:
Muskmelon plants near infested cotton were well provided with
aphides, several of the wingless ones being found with young about
them. Turnip plants near infested cotton had few aphides on
40842-Bull. 85, pt 6-10--2
102 PAPERS ON CEREAL AND FORAGE INSECTS.
them. Cowpeas were lightly infested with all stages, except mi-
grants, although not located near heavily infested cotton. On beans
near infested cotton there were only a few of the root-aphis. Sweet
corn had been planted along a row of cotton, and this was quite gen-"
erally infested with the lice," plants that were near dead cotton
being most heavily infested. On radish, a colony was found on one
plant growing near badly infested cotton. Watermelon plants
which had just unfolded their first leaves and were near infested cot-
ton had an abundant supply of the root-aphis. In the case of each of
the cultivated plants mentioned above, Mr. Ainslie found evidence
that the lice were transferred from the cotton to the others by the
ants. The ants found in attendance were Lasius niger americanus,
Pheidole dentata comutata, and Pheidole vinelandica.
UNCULTIVATED FOOD PLANTS.
Beside the cultivated plants mentioned above, the root-aphis feeds
on various uncultivated species which are enumerated below.
In Illinois it has been reported by Mr. J. J. Davis a on the roots
of numerous weeds and grasses, as follows: Smartweed (Polygonum
lapathifolium), knotweed (Polygonumn persicaria), crab grass (Digi-
taria sanguinalis), purslane (Por'tulaca oleracea), dock (Rumec
c(ispus and R. altissimus), foxtail or pigeon grass (Setaria glauca
and S. viridis), fleabane (Erigeron canadensis), mustard (Brassica
nigra), sorrel (Oxalis stricta), plantain (Plantago major and P.
rugelii), pigweed (Amaranthus hybridus), and ragweed (Ambrosia
In the South it has been found on the following wild food plants:
At Chattanooga, Tenn., November 25, 1909, a few oviparous females
were found on thorny amaranth (Amaranthus spinosus). Vivip-
arous females were found on green amaranth (Amaranthus retro-
flexus) in a cornfield at Salisbury, N. C., October 12, 1909, in small
numbers. It was found rarely on Roman wormwood (Ambrosia
artemisiifolia) at Nathalie, Va., by Mr. J. A. Hyslop, July 10, 1908.
It was found in large numbers on the roots of Ambrosia artemisiifolia
in cotton fields and in waste ground at Marion, S. C., May 27 to June
5,1909, and at Salisbury, N. C., May 22 and September 18, 1909. On
this plant they usually fed in fair-sized col6nies along the main tap-
root, sometimes 10 inches deep in the ground. It was found on dog
fennel (Anthemis cotula) in very large colonies at the base of the
large roots, near the crown, at Marion, S. C., on May 29, 1909; on
shepherd's purse (Capsella bursapastoris) in small numbers at Salis-
avDavis, John June-Biological Studies on Three Species of Aphidide. Tech. l
Ser. No. 12, Part VIII, Bur. Ent., U. S. Dept. Agr., February 20, 1909.
b Records from Marion, S. C., are by Mr. G. G. Ainslie; those from other
localities are by the writer, unless otherwise stated.
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
bury, N. C., June 16, 1909; on lamb's-quarters (Che7nopodium album)
growing near a field of popcorn at Nathalie, Va., by Mr. Hyslop,
July 10, 1908, and on the same species growing beside a cornfield at
Salisbury, N. C., October 9-22, 1909-in large numbers at both
places; on poverty weed (Diodia teres) in a cornfield at Salisbury,
N. C., July 28, 1909; on buttonweed (Diodia rirginiana) in a corn-
field at Salisbury, N. C., September 25, 1909; on foxtail or pigeon-
grass (Setaria glauca) at Marion, S. C., June 3, 1909; in small num-
bers on cudweed (Gnaphalium purpireurm) at Salisbury, N. C., May
22, 1909, and in large numbers on this plant at Marion, S. C., from
May 26 to June 14. 1909. It was numerous on sneezeweed (Helen unm.
tenuifoliumn) at Rockmart, Ga., November 23, 1909, and at Marion,
S. C., May 29 to June 25, 1909; this plant, growing in open ground,
and in cotton and corn fields, was the most commonly infested weed,
and was heavily infested by the aphis in all stages. On pineweed
(Hypericum. gentianoides) it was found in small numbers at Marion,
S. C., May 26. 1909. It was abundant on dwarf dandelion (Krigh'
virginica) at Marion, S. C., May 26, 1909; large colonies were found
near the crown of the plant, but individuals were sometimes deep
down on the fibrous roots. It was found on Leptorhloa filiformis at
Salisbury, N. C., September 13, 1909. On peppergrass (Lepidi/m
apetalum) at Ringgold, Ga., November 24, 1909, a few only were
found. Lepidiutm virginicutm was a favorite food plant for this in-
sect at Marion, S. C., May 29 to June 14, 1909. It was found rarely
on toadflax (Linaria canadensis) at Marion, S. C., from May 26 to
June 1, 1909, and abundantly on plantain (Platitago aristata) at
Marion, S. C., June 3, 1909. It was numerous on plantain (Plantago
major) at Sharpsburg, Md., July 9, 1907, according to Mr. Kelly, and
at French Creek, W. Va., November 20, 1908, as reported by Mr. F. E.
Brooks in a letter to the Bureau. It was found on water pepper
(Pol.ygonum hydropiperoides), May 22, 1909, and on another of the
knotweeds (Polygonum muhlenbergii), October 16, 1909, at Salis-
bury, N. C., but was not numerous on either of these plants; it was re-
ported also as abundant on purslane (Portulaca oleracea) at French
Creek, W. Va. It was abundant on poverty weed (Diodia teres), at
Marion, S. C., May 31 to June 14, 1909, as nearly every plant of this
species was infested; it occurred also on cocklebur (Xanthiuim cana-
dense) at Marion, S. C., June 1, 1909.
This insect has been reported and described from Colorado by
Cowen on the roots of mint (Merntha arvensis) under the name of
Aphis men th(Pe-radici4s.
All the known wild food plants infested by this species are native
to the eastern United States except the following: Amnaranthus retro-
flexus8, A. spinosus, and A. hybridus, which have been naturalized
PAPERS ON CEREAL AND FORAGE INSECTS.
from tropical America; and Chenopodium album, Capsella bursa-
pastoris, Brastica oleracea, and B. nigra, Polygonum persicaria,
Rumex crispus, and Anthemis co-
\ tula, which are adventitious from
Europe or have been naturalized
from Europe. They are all annuals
Sbinilexcept a few which are sometimes
a a biennials.
0o. During March and April, 1910, in
Odo the vicinity of San Benito, Tex., the
0 > writer found this species infesting
o 0', the roots of the following unculti-
iSvated plants: Vervain (Verbena
00 canadensis), common nightshade
a go 0 g(Solanum nigrum), skullcap (Sew-
tellaria drummondii), Teucrium
laciniatum, amaranth (Armaran-
t^/h/.s sp.), Sqelenma (?.) sp., and at
FIG. 56.-The corn root-aphis: Ovipa- thus sp.), Selenia (?) sp., and at
rous female and hind tibia. (From Brownsville on the roots of Iva
Forbes.) xanthifolia (?).
Nothing was found to indicate that it had attacked either corn or
cotton, although further investigations will be required to either
prove or disprove its occurrence on
these or other cultivated plants.
INJURY TO CORN.
Aphis maidi-radicis has been par-
ticularly injurious to corn in Mary-
land, Ohio, Indiana, and Illinois, and
has done serious injury to this crop
in eastern Pennsylvania, New Jersey,
the Virginias, and the Carolinas. In
badly infested fields the crop is some-
times almost entirely lost. as shown in f
the accompanying illustration (Plate
V, fig. 1), from a photograph by Mr. 0 I
W. J. Phillips, of a field in Indiana. t
In Illinois its seasonal history, ac-
cording to Mr. J. J. Davis,a is, in brief,
as follows: The eggs may be found F 57.-The corn root-aphis: Wing-
less male and antenna. (From
hatching in the field from April 8 to Forbes.)
May 22, and from ten to twenty-two generations may follow. Sexual
forms (figs. 56-58) are produced in the latter part of September or in
Bul. 85, Part VI, Bureau of Entomology, U. S. Dept. of Agriculture.
FIG. 1.-DAMAGE TO A FIELD OF CORN IN INDIANA IN 1906 BY THE CORN ROOT-APHIS
APHISS MAIDI-RADICIS). (ORIGINAL.)
FIG. 2.-SAME FIELD A YEAR LATER, SHOWING THE EFFECT OF APPLYING BARNYARD
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
October, and eggs are laid in October and November. The eggs do
not hatch until the following spring. Its seasonal history in other
parts of the country does not appear to vary materially from that in
RELATION OF ANTS TO THE ROOT-APHIS.
The life of the corn root-aphis in the cornfields is so dependent
upon that of the cornfield ant (Lasius niger L., var. americanus
Emery), and vice versa, particularly in the Middle West, that they
must be considered together. If it were not for this ant the great
damage that is dofie to corn in this country by the root-aphis would
be impossible. The ant is distributed everywhere over North Amer-
ica except in the extreme southern and southwestern portions. It is
found in cultivated fields, in pastures, in forests, and along roads.
A very complete account of the life history of this ant is given by
Doctor Forbes in the Twenty-fifth Report of the State Entomologist
The ants collect the eggs of the aphis in the fall and carry them
to their nests, where they are kept during the winter. By bringing
these eggs near the surface or carrying them deeper down into their
burrows the ants are able to control the hatching of these eggs until
weeds spring up upon which the young aphides can feed. As soon
as the eggs hatch the young larvae are transferred to the roots of
young weeds such as pigeon grass, smartweed, and ragweed. When
the corn begins to come up the colonies of the root-aphis are trans-
ferred to the roots of corn. The root-aphis, like all other species in
this family, secretes and voids a sweet liquid called honeydew, upon
which the ants feed. As this honeydew constitutes the principal
food of the ants, the strength of each individual ant colony is de-
pendent upon the number of aphides in its charge.
- Although Lasius niger americanus is the most important ant that
attends Aphis maidi-radicis throughout the territory known to be
infested by the root-aphis, it is not the only one thus involved. Two
other species that are important in this connection are Lasius flavus
Fab., which has often been observed attending the root-aphis in
Maryland, and Pheidole vinelandica Forel, which was observed by
Mr. J. A. Hyslop attending it at Nathalie, Va., and by Mr. G. G.
Ainslie, at Marion, S. C. Among the ants which sometimes attend
this species are Lasius (Acanthomyops) murphy Forel found asso-
ciated with this species at Arlington, Va., by Mr. Paul Hayhurst,
and the following species, which are reported by Doctor Forbes a as
occasionally attending the root-aphis in Illinois: Formica schaufussi
a Eighteenth Report of the State Entomologist of Illinois. Trans. Dept. Agr.
Ill. for 1893, Springfield, vol. 31, p. 66, 1894.
106 PAPERS ON CEREAL AND FORAGE INSECTS.
Mayr, Lasius in terjects Mayr, Myrmnica seabrinodis Nyl., and Sole- ,
nopsis debilis Mayr.
NATURAL CHECKS. I
There are no natural checks to the multiplication of the corn root- .
aphis and its attendant ant except hard, beating rains that are long
continued. The thorough soaking of the ground by such rains
drowns out many of the aphides, and also the young of the ants.
It happens that over the entire territory infested by the corn root-
aphis the best cultural methods for the growing of corn independent
of insect injury are just the methods that reduce the numbers of the
corn root-aphis and its attendant ant. These methods are crop
rotation, maintenance of soil fertility, and early plowing, followed
by frequent cultivations.
The system of rotation that gives the shortest time in corn is the
best. In the cotton belt the injury from the root-aphis will be less
if cotton and corn are not allowed to follow each other in rotation.
Outside the corn belt it makes no difference what the rotation is from
the standpoint of root-aphis injury, because no other field crop is
injured by this insect. When an old cornfield is sown to some rota-
tion crop, such as one of the small grains, the ants are unable to
find food for the aphis except on the roots of weeds, which are soon
killed out by the attacks of the aphis, or are smothered by the grain.
Large numbers of the aphis will then acquire wings and leave the
field. There is some evidence that others are eaten by the ants, but,
one way or the other, the field is freed of them.
MAINTENANCE OF SOIL FERTILITY.
The maintenance of soil fertility by the direct application of ferti-
lizers does not lessen the numbers of the aphis, but by furnishing the
corn plant with sufficient food it enables it to make a strong growth
and mature a crop in spite of the aphis. This benefit is shown in
the illustrations (Plate V), from photographs taken by Mr. W. J.
Phillips at Richmond, Ind.
EARLY PLOWING, FOLLOWED BY FREQUENT CULTIVATIONS.
In order to reduce the numbers of the root-aphis old cornfields
in the Northern States should be plowed in the fall or early spring,
and then the ground should be stirred several times before planting,
with a corn cultivator or disk harrow. The burrows of the ants
infrequently go deeper into the ground than 6 inches, so that if the
ground is turned over and thoroughly stirred their nests are broken
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
up and the contents so scattered that the ants are able to recover only
a few of their own eggs and larvae, and fewer yet of the aphis eggs.
This method also prevents the weeds from getting a start, so that
there is no food for the young larvae which hatch from those eggs
which the ants are able to preserve. This is a good treatment for
land that is to be planted to corn throughout the section of country
where the'root-aphis is found, but more especially in the northern
part of the infested territory.
In the more southern part of the range of this insect winter plow-
ing may be practiced with good results wherever the land is suffi-
ciently level so that it will not wash badly. Winter plowing breaks
up the ants' nests and scatters the contents of these nests at a time
when the ants are least able, because of the cold wet weather and
shortness of the food supply, to recover from the injury.
One example of the effects of winter plowing that came under the
observation of the Bureau of Entomology was as follows: Mr. John
Bowie, at Annapolis Junction, Md., plowed the major portion of a
60-acre field in the winter of 1905-6, leaving unplowed a small strip
in the middle, which he finished in the spring. Prof. F. M. Webster
visited this field July 28, 1906, and found that owing to injuries by
the root-aphis the spring-plowed portion of the field would almost fail
to produce a crop, while the winter-plowed portion gave promise of
an unusual yield. On the spring-plowed area much of the corn was
missing, while many of the surviving stalks were dwarfed. By these
signs it was easy to determine at a glance the dividing line between
the two areas. On September 22, 1906, just after the corn was cut
and shocked, this field was visited by Mr. C. N. Ainslie, and hlie, too,
was able clearly to separate the two areas, being guided only by thi
appearance of the stubble.
In the southern part, of its range the corn root-aphis is able to
spend the entire summer on its wild food plants, and these wild
plants are especially infested in the late summer and early fall. If,
then, these weeds are destroyed by thorough cultivation, the root-
aphis is encouraged to leave the fields. In the fall eggs are laid on
the roots of late scrub corn which was not harvested and on the roots
of weeds such as Ambrosia and pigweed. Fall plowing as soon as
possible after the crop is harvested will prevent these eggs from being
laid in the field. The land may then be put into some cover crop.
The method of combating the root-aphis by direct application of
repellents to the seeds was investigated by Doctor Forbes and re-
ported in the Twenty-fifth Report of the State Entomologist of
Illinois. Many substances were experimented with, such as oil of
lemon, oil of cloves, kerosene, and carbolic acid. Of these, oil of
108 PAPERS ON CEREAL AND FORAGE INSECTS.
lemon appears to be most promising. A solution of the oil in alco-
hol-1 part of the oil to 9 parts of ordinary commercial alcohol-is
used. About 3 ounces of this mixture is used to a gallon of corn. It
should be stirred thoroughly till all the seed is moistened. This
treatment costs only 10 cents an acre for the materials, and appears
to be very effective.
INJURY TO COTTON. i
A form of .iphis maidi-radicis was very injurious to young cotton
on the light sandy soil of the eastern parts of North Carolina and
South Carolina throughout the seasons from 1907 to 1909. During
this time it was the most injurious enemy of cotton in that region.
In this form, which is apparently the same as that found on corn at
Duncan, Okla., by Mr. T. D. Urbahins, of this Bureau, the spots on
the back of the apterous vivipara are larger and darker than they
are on the typical ;lpliis maidi-radicis as found on corn roots in
Illinois. The third antennal segment has two or three circular sen-
soria which are not present in the Illinois variety. Although this
insect was first brought to the attention of entomologists as a cotton
pest in 1907, some of the cotton planters in North Carolina have
known of it for upward of twenty years.
It attacks cotton just as soon as the young plants appear above
ground and is usually first noticed when the plants are about 2 inches
high. The cotton plants in certain areas will turn red and die,
shriveling utip so that they can be seen with difficulty. In one field,
examined May 28, 1909, at Marion, S. C., by Mr. G. G. Ainslie, fully
90 per cent of the cotton was infested. As a rule most of the aphides
observed were in a cluster on the main stem just below the surface
of the ground, but a few could be found anywhere on the roots, even
to the tips of the longest rootlets. Mr. Ainslie found as many as
200 insects, in all stages, on one plant.
As far as the study of this insect has gone it appears that the
root-aphis infests cotton only while the plants are young and tender,
and leaves as soon as the roots begin to get hard and woody; or they
remain only on the fibrous rootlets deep down in the soil where they
are unable to do much damage. They leave the plants as winged
migrants or are transferred by the ants to some of the numerous
wild food plants of this species.
The ravages of this insect in the cotton fields can be largely pro- I
vented by proper rotation and better cultivation. Most of the .
planters reported that the insect was less injurious where cotton was
grown after cotton. This is because the cotton fields are usually well
cultivated, so that when the root-aphides leave the cotton plants they
leave the cotton fields, and their eggs are not left in the fields in the
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
Many of the planters report that cotton is more seriously injured
when it is planted after corn. This is because the root-aphis can feed
on the roots of corn all summer and also because the cornfields are
not kept clear of the wild food plants of this insect. For this reason
the aphides can find an abundant food supply in the cornfields all
summer. In cornfields as far south as Salisbury, N. C., the eggs of
this aphis are laid on the roots of late replanted or scrub corn which
was left uncut, or more often, perhaps, on the roots of its wild food
plants. These eggs are then taken into the burrows of the ants and
cared for by them during the winter. When these eggs hatch in the
spring, the young larvae are placed by the ants on the roots of cotton
or corn, if these crops are up; if not, they are placed on weed roots
and live there for a while, and most of them are transferred to the
roots of corn and cotton as soon as these plants become available.
If corn is to be followed by cotton, it will be best to plow the land
as early as possible in the fall and to sow to a cover crop later. This
will prevent the eggs of the root-aphis from being laid in the field,
while the plowing and cultivation will break up the nests of the ants
and prevent them from caring for the eggs that are laid. The
borders of the field should be kept as clear of weeds as possible.
INJURY TO ASTERS.
The first record we have found regarding the injury of a root-
aphis to the Chinese or German aster is in an article on The culture
of the aster," by Edward S. Rand,, in which he says:
The earth should not be sandy, as in such soil they are very subject to the
attacks of a root-aphis, which always proves fatal to the plant.
For the root-aphis which troubles the plant in sandy soils we know of no
remedy but to dig up the affected )ilant and destroy the insect.
From this it appears that the root-aphis was well known as a
serious enemy of the aster in New England as early as 1858, or only
about thirteen years after the China aster became numerous there.
A later record is found in the Practical Farmer for 1875, an extract of
which is given in the Horticulturist and Journal of Rural Art and
Taste,b where mention is made of the dusty louse" which is found
at the roots of German asters in hot, dry weather." Watering the
asters heavily is mentioned as a remedy.
The first record in the files of the Bureau of Entomology in regard
to this pest on asters is an inquiry from Washington, D. C., in July,
1899. Since then inquiries have come from the following States:
a Trans. Mass. Hort. Soc. f. 1858, pp. 26, 27.
b Horticulturist and Journal of Rural Art and Taste, vol. 30, p. 366, 1875.
110 PAPERS ON CEREAL AND FORAGE INSECTS. i
Massachusetts, Connecticut, Rhode Island, New York, New Jersey,
Delaware, Maryland, West Virginia, Ohio, and Illinois.
Mr. J. A. Kreutzberg, writing from Chicago, Ill., September 9, i
From 500 to 1,000 plants grown from seed early every year in the hotbed,
and in due time transplanted in the open ground, rarely more than one-third :
survive and pull through to full growth and beauty. The trouble appears to
be a small green louse which looks like the aphis which infests the rose bushes,
lodging in the roots, forming large colonies in them, and working their way up
in the plants to the surface of the ground. Some of the plants are blighted as
soon as they are set in the open ground, some later, and some when the plants
are in full bloom. The moment that the plants are attacked by these parasites
they show it by turning yellow and wilting down to the ground.
In a later letter, September 15, 1908, he says:
I this morning pulled up three aster plants which were in full bloom, yet
showed the taint of the ravages of the aphis, which apparently did not attack
the plant until quite recently. In looking over my aster field this morning
I find that nearly every plant is affected, which was conclusive proof to me that
these little pests begin their attack during all stages of growth of the plants.
Some are attacked immediately after transplanting to the open ground, others
a little later on, and some that seem to have strength enough to pull through
and are iu bloom are attacked after the bushes are loaded with flowers. These
three plants that I pulled today were loaded with the insects, but of a different
color than I have found them heretofore, but apparently the same genus.
The other reports are much the same. The aphides apparently at-
tack the asters as soon as they are set out in the open and feed on
them till the sexual forms appear and the eggs are laid in the fall.
The correspondents often report that the aphides are attended by
ants, but only one species has been taken and identified. Lasius alie-
nis Fbrst was sent to the Bureau by Mr. C. R. Cranston from Provi-
dence, R. I., with the following information:
Just as the [aster] buds begin to form, the leaves all turn yellow and the
plant never blooms. On pulling some up I found that ants had taken green
plant lice under ground to suck the sap from the roots.
It should be easy to keep the asters free from this pest if the fol-
lowing precautions are taken: Choose for the aster bed ground that
has not grown asters or corn for the past year. Free this ground
from the wild food plants of this species some time during August.
Then, if there is no crop on the ground, it may be cultivated, covered )
with manure, and left till next spring. The only way for the aphis
to reach the plants on this ground would be for the winged migrants
to fly to the plants and then be captured and taken to the roots by
ants. It is extremely improbable that those reaching the plants in
this way could increase in numbers fast enough to do serious injury. :'
In fact, if the asters are planted in ground which has not grown
asters or corn the past year, and which is not located near a field of
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
corn or an infested aster bed, they will not be troubled with this pest,
provided the wild food plants of the pest were removed from the
vicinity of the bed as mentioned above.
OTHER CULTIVATED FOOD PLANTS.
A root-aphis was reported, in October, 1908. by the M. Crawford
Company, of Cuyahoga Falls, Ohio, to be injuring strawberry plants
in a field which had been in corn the year before. This aphis was
identified by Mr. Theo. Pergande as Aphis maidi-radicis.
Mr. C. H. Popenoe, of this Bureau, collected it from the roots of
cabbage at Doncaster, Md., July 24, 1907. These specimens were
also identified by Mr. Pergande as Aphis maidi-radici..
These aphides were found to be injurious to pumpkin and water-
melon at French Creek, W. Va., in July, 1908, as reported in a letter
from Mr. F. E. Brooks:
I have found the aphis on roots of watermelon and pumpkin growing where
an old sod of orchard grass was plowed down last spring. The cucurbits grew
about 100 yards from a cornfield that was infested last season.
What is supposed to have been Aphis maidi-radicis was reported
from Dover, Del., to be injuring French artichoke. Mr. Theophile
Berneau, of Dover, in a letter to the Bureau of Entomology, August
25, 1908, says:
I am cultivating French artichoke, Cynara scoliym us, and have some trouble
with minute insects which settle on the roots and suck the sap, to the great
detriment of the plant.
Mr. Berneau reported that these insects were accompanied by a
great number of ants.
This species was reported as injurious to dahlia at Longmeadow,
Mass., and at Springfield, Mass., in 1906. In a letter from Spring-
field dated June 4, 1906, Mrs. T. G. Forster says:
I have set out a few dahlia bulbs and find they will not grow. To-day on
unearthing some of them I find the roots and also the sprouts-the part in-
side the ground-covered with small white lice which seem to eat the small
new roots as they start to grow. Have had some trouble with themni before.
DESCRIPTION AND SYNONYMY.
There is some question as to whether, in our study of this insect,
we are dealing with one or with more than one species. There is a
form which feeds on the fleabanes (Erigeron) and on wild asters,
described by Cyrus Thomas in 1879 as Aphis middletoni. This is
probably a distinct species, although further study may show that it
is the same as Aphis maidi-radicis, in which case both forms would
be known as Aphis middletoni Thos.
Specimens found on the roots of corn, in Oklahoma, by Mr. T. D.
S Urbahns, of this Bureau, and on cotton, ijn South Carolina, by Mr. G.
PAPERS ON CEREAL AND FORAGE INSECTS.
G. Ainslie, at that time a special field agent of this Bureau, are about
the size of the typical Aphis maidi-radicis but they have circular
sensoria-usually about three on the third segment of the antenna-
and have larger and darker markings on the thorax and abdomen
than has the typical Aphis maidi-radicis. This form is without much
question only a variety of the true Aphis maidi-radicis. It seems
best at the present time to recognize two species, viz, Aphis middle-
toni Thos., feeding on plants of the genera Aster and Erigeron, and
Aphis maidi-radicis Forbes, which feeds on corn, cotton, and many
FIG. 58.-The corn root-aphis: Winged male. greatly enlarged, and antenna, highly magni-
Mr. J. H. Cowen describes an aphis under the name of Aphis
mentha-radicis which was taken on Mentha canadensis at Hotchkiss,
Colo., July 14.a This is the same as the form on the roots of corn, and
must therefore be considered a synonym of Aphis maidi-radiis. In
a recent letter Prof. C. P. Gillette, entomologist of the experiment
I have compared the type specimens with the slide (Aphis ilaitdt-radifsa)
you sent, and am a little in doubt as to whether there is sufficient difference to
consider the lice from the mint as a different species. I hardly think they are.
It also seems that Mr. Cowen's armnioracea is also in all probability Mnaidi-
radicis, but before finally deciding this matter I should like to compare the
a Description published in "A Preliminary List of the Hemiptera of Colorado."
By C. P. Gillette and Carl F. Baker. Bul. 31, Colo. Agr. Exp. Sta., p. 121, 1895.
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
living lice from the different plants. Arnoracea we have found very abundant
here on horse-radish.
As very complete descriptions of the different forms of Aphis
maidi-radicis have been published, no descriptions are given in this
paper except that of the winged male, which has not been before ob-
served or described. Two of these males appeared in the vials in
which Aiphis maidi-radicis from the roots of Ambrosia artemisiifolia
were being reared onil corn, and one in the vial of Aphis from Lep-
tochloa filiformnis. Two of these were used in experiments; the other
was preserved and is described below.
Winged S (fig. 58S).-Head, thorax, eyes, and appendages black. Abdomen
green, with dark transverse bars on the dorsal side of the 5th, 6th, and 7th
somites. The beak reaches the metathorax. The antennae reach the caudal
end of the second abdominal somite. The circular sensoria are arranged on
the antenna as follows: 24 on the third, 12 on the fourth, 7 on the fifth, 4 on
the sixth. Length of body, 1.50 rmm.; length of wing, 1.75 mm.; length of cor-
nicle, 0.10 mm. (Measurements made from specimen mounted in balsam.)
In 1856 Doctor Fitch described the corn leaf-aphis (Aphis Pmaidis),
and up to 1891, when it was described by Doctor Forbes, what is
now known as Aphis maidi-radicis was supposed to be only a root
form of that found on the leaves. No one, however, has been able
to trace a sexual relationship between the two. Although the sexual
forms of A. maidis have never been observed, it does not seem
possible that such a relationship as was previously supposed can
really exist. Besides, while, as shown by map on page 114, A phis
maidi-radicis is confined to the country east of the one hundredth
meridian, Aphis maidis occurs from Maine to southern California.
THE ERIGERON ROOT-APHIS.
(Aphid in middletoni Thos.)
The species Aphis middletoni Thos. is considered here because it
has usually been identified as Aphis maidi-radicis in publications; and
because it is impossible to study one of these forms on various food
plants over a wide extent of country without studying the other.
So far as is now known Aphis middletoni infests normally plants
of the genera Aster and Erigeron, usually in very large colonies at
the crown of the plant just below the surface of the ground or on the
large roots. The only cultivated plants it has been known to attack
are Cosmos bipinnatus and the China or German asters (Callistephius
hortensis), and possibly also dahlias and French artichoke (Cynara
Aphis middletoni was first described by Cyrus Thomas, in 1879, in
the Eighth Report of the State Entomologist of Illinois. Since then
it hag been referred to in literature only in food-plant lists. It has
PAPERS ON CEREAL AND FORAGE INSECTS.
generally been confused with the corn root-aphis, and when found on
any other plant except Erigeron it has usually been identified as
Aphis maidi-radicis. It is much smaller than the latter species and
is usually more heavily powdered with a waxy material. Its corni-
cles are about one-half the length of those of the corn root-aphis..
The third antennal segment in the apterous, viviparous female has a
group of 5 or more circular sensoria, and there is also a group of cir-
cular sensoria on the fourth, and sometimes also on the fifth segment.
In the typical Aphis maidi-radicis these circular sensoria'are not
present. The winged vivipara are smaller than those of Aphis maidi-
radicis, have shorter cornicles, and circular sensoria on the third,
I I ^ r *I9
I I a 0 I I
\ ----------------------- ----I.4,. '*f ^-~
-4. ,,6, *.... | . .-,,_ -
I --, --- -.------- .
,. \, --. * %. : / , : *-
*I I I -Ie -
II -I SI I S g U
\ ....9 I 2. ,
I I S . aq I
0 1 e
-" ,L ...- gi < *._..\%
Fir.. 511.-Map showing distribution of Aphis maidi-radicis and Aphis middletoni in the
United States. From the records of the Bureau of Entomology. 0 Localities in which
Aphis maidi-radicis has been found or reported on the roots of corn. x Localities In
which Aphis mnaidi-radicis has been reported injurious to asters. U Locality where
Aphis maidi-radicis was found on uncultivated plants only. 0 Localities in which
Aphis middletoni has been collected.
fourth, and fifth antennal segments, while Aphis maidi-radicis has
these sensoria only on the third segment. The same differences are
found in the oviparous females. '
This species appears to have been a native of the Great Plains, but
is now distributed widely over the territory east of the Rocky Moun-
tains, as is shown in figure 59.
UNCULTIVATED FOOD PLANTS..
Aphis middletoni has been found on the following wild food
plants: On Erigeron canadensis, mostly in the Northwest; on
Erigeron rarmosus, in the Carolinas; on the roots of Aster subulatus 7;
at Salisbury, N. C., from May 22 until September 22, 1909, and on
CONTRIBUTIONS ON THE CORN ROOT-APHIS.
Aster ericoides, from September 18 until November 15, 1909. Sexual
forms were found on this plant at Salisbury, N. C., November 15,
1909, and at Rockmart, Ga., November 23, 1909. Cosmos (Cosmos
bipinnatus), which had escaped from cultivation and was growing
wild along the roadside at Salisbury, was also found infested by
this aphis in October, and on November 5 sexual forms were present
on the roots of the plant.
CULTIVATED FOOD PLANTS.
Specimens of an aphis which attacked the roots of China asters
(Callistephus hortensis), received from Dr. E. P. Felt, of Albany,
N. Y., apparently belong to this species, but specimens collected from
the roots of cultivated aster at Chicago by Mr. J. J. Davis are with-
out any doubt Aphis maidi-radicis. It is yet an open question to
which species the insect which has been attacking cultivated asters
in the North Atlantic and New England States belongs. The species
which attacks dahlias and French artichokes (Cynara scolymus)
belongs to one of these two, but to which one can only be settled by
obtaining more material. Cosmos bipinnatus was found infested
by Aphis middletoni October 6, 1909, at Salisbury, N. C. The writer
has found no record in the American or foreign literature of an
aphis infesting the roots of dahlia, artichoke, or cosmos. Cosmos
bipinnatus, which grows wild in Mexico, may have been one of the
original food plants of this species.
The Erigeron root-aphis is attended by a larger number of ant
species than is Aphis maidi-radicis. It is seldom found associated
with Lasius niger L. var. americanus Emery, which commonly attends
the corn root-aphis, but is ordinarily found attended by a medium-
sized black ant, Cremastogaster lineolata Say, which on the other
hand seldom attends the corn root-aphis.
Lasius niger americanus was observed associated with this species
by. Mr. J. A. Hyslop at Nathalie, Va., July 9, 1908, and by the writer
at Salisbury, N. C., on Cosmos bipinnatus November 5, 1909, and on
Aster ericoides November 15, 1909.
Cremastogaster lineolata was observed associated with this root-
aphis by the writer at Salisbury, N. C.; by Mr. G. G. Ainslie at
Clemson College, S. C., and by Mr. Paul Hayhurst at Ponca City,
Okla., Newkirk, Okla., and Wellington. Kans. At Winfield, Kans.,
it was found by Mr. Hayhurst associated with the varieties of this
ant known as opaca and clara. This ant and aphis were also found
associated at Wellington, Kafis., by Mr. E. 0. G. Kelly.
116 PAPERS ON CEREAL AND FORAGE INSECTS.
The following ants were found associated with this species on the i
roots of Erigeron canadensis: By Mr. Hayhurst-Pheidole sp. at .
Arkansas City, Kans., Solenopsis geminata Fab. and Dorymyrmew 4
pyramicus Roger at Kingfisher, Okla., and Iridomyrmex analis Emrn, .
at Newkirk, Okla.; by Mr. Kelly-Solenopsis molesta Say, Lasius i
interjectus Mayr, Monomorium minutum Mayr var. minimum Buck-
ley, and Ponera coarctata Latr. var. pennsylvanica Buckley, at Wel-
lington, Kans.; by Mr. G. G. Ainslie-Pheidole vinelandica Mayr at "
Marion, S. C. The ant Prenolepis imparts Say was found by the
writer associated with this root-aphis on Aster ericoides at Rock-
LABORATORY AND FIELD EXPERIMENTS.
Many laboratory experiments were carried on by the writer at
Salisbury, N. C., to determine the adaptability of Aphis middletoni
to other food plants. Wingless females were taken from the roots of
Erigeron ramosus and transferred to sprouting corn and to sprouting
cotton in vials, and although this experiment was tried several times,
using several females each time, it was unsuccessful. A number of
experiments were tried, using the females from the roots of Aster
subulatus. These also were unsuccessful, with the following single
exception: Females removed from the roots of Aster subulatus to
sprouting cotton, August 30. produced young which succeeded in
supporting themselves on the cotton. Several generations were pro-
duced, but the aphides never acquired the characters of Aphis maidi-
radicis. Oviparous females were produced October 9 and others were
produced later, the experiment being closed November 22.
Mr. Kelly carried on similar experiments at Wellington, Kans., in
1908, which were more successful. His experiments, in brief, are as
Experiment D.-A stem-mother was removed from the roots of a young
Erigeron plant May 9 and placed on a young Erigeron plant in a vial. The
young which she produced were placed on sprouting corn in vials.
Experiment D'.-One young born May 10(?) became adult May 19 and pro-
duced 45 young between May 20 and June 7.
Experiment F1.-One larva removed from cage D May 12, matured May .
22( ?), and produced 35 young from May 22 to June 2.
Experiment F.-One larva from cage FV, born May 22, matured May 30, and
produced 32 young from May 30 to June 7.
Experiment F3.-Larvae removed from the above experiment May 30 did not
mature on corn.
Mr. G. G. Ainslie carried on similar experiments in 1908 at Clem-
son College, S. C. The most successful experiment was as follows:
A few aphides from the roots of Erigeron canadensis were placed
on sprouting corn in a vial, October 30; by November 9 four young N
CONTRIBUTIONS ON THE CORN ROOT-APHIS. 117
had been produced and on November 20 one wingless viviparous
female remained alive. The experiment was closed November 20.
These experiments show that the Erigeron aphis can be transferred
to corn or cotton roots and will live on these plants. It seems to take
to these plants more readily early in the spring or late in the summer,
when a migration from a wild food plant is about to take place. The
fact that, when grown on corn, this aphis still retains its distinctive
characters, instead of acquiring the characters of Aphis maidi-radicis,
goes to show that these two are distinct species.
Mr. Hyslop and Mr. Kelly carried on experiments of a different
nature for the purpose of determining these points.
Mr. J. A. Hyslop, on July 29, 1908, found specimens of Erigeron
canadensis in the grounds of the U. S. Department of Agri-
culture at Washington, D. C., badly infested with this aphis. Near
these plants he planted corn, watermelon, and cucumber seeds. On
September 23 he pulled all of these plants. The Erigeron plants
were infested, but no aphides were found on the other plants, even
though the roots intermingled in many instances.
On August 11 Messrs. Kelly and IUrbahns, at Wellington, Kans.,
planted corv, squash, cucumber, and watermelon near an infested
Erigeron plant. These plants were watched till October 12, during
which time the aphides continued on the Erigeron, but were found
at no time on the other plants.
Mr. Kelly, at Wellington, Kans., on August 26, 1908, planted corn,
watermelon, cucumber, squash, and pumpkin seeds near infested
plants of Erigeron canadensis. He examined these plants, Septem-
ber 29, but found aphides only on the Erigeron, although the roots of
the plants often intermingled.
These experiments show that under natural conditions in the field
this aphis will not change from the Erigeron to the corn. What it
would do if forced to leave the Erigeron is uncertain, but we have
no evidence thus far that it can live for any very long time on the
roots of corn.
1While making a trip through the Northwest, in June, 1908, for the
purpose of studying the insects affecting cereal and forage crops, Mr.
Kelly made a careful study of Aphis mnaidi-radicis and A. mid-
dletoni. At Hastings, Kearney, Columbus, and Fremont, Nebr., and
at Missouri Valley and Marshalltown, Iowa, Aphis mnaidi-radicis
was common on the roots of corn; but although Erigeron can adensis
was plentiful, the roots sometimes intermingling with the roots of
corn, there were no aphides on the roots of Erigeron. At Bismarck,
N. Dak., and Norton and Phillipsburg, Kans., the Erigeron plants
were common and had aphides on their roots, but there were no
aphides on the roots of corn.
PAPERS ON CEREAL AND FORAGE INSECTS.
At many of the towns visited neither species was found, although '
their food plants were plentiful. If these two forms were con-
sidered to be one species these results would be very difficult to
At Salisbury, N. C., a colony of these aphides on Aster subulatus
was found parasitized by a species of the hymenopterous genus
Lysiphlebus. This colony was at the crown of the plant near the
surface of the ground.
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