The oak pruner (Elaphidion villosum Fab.)

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Title:
The oak pruner (Elaphidion villosum Fab.)
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Book
Creator:
Chittenden, F. H ( Frank Hurlbut ), 1858-1929
United States -- Dept. of Agriculture
United States -- Bureau of Entomology
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Govt. Print. Off. ( Washington )
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aleph - 029685848
oclc - 27940713
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Full Text







LIBR ARY
STATE PLANT BOARD


1s3u1,P] December 10, 191').


U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ENTOMOLOGY-CIRCULAR No. 130.
L. 0. HOWARD. Entomologist and Chief of Bureau.


THE


OAK


PRUNER.


F. H. CHITTENDEN, Sc. D.,
In Charge of Trurk Crop and Stored Product Insect Inrcsfigations.


WASHINGTOi : GOVERNMENT PRI%TI%G OFFICE : 1910


65401--10


f%33






















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. CLIFrON, Executive Assistant.
W. F. TASTET, Chief Clerk.

F. H. CHITTENDEN, in charge of truck crop and stored product insect investigations.
A. I). HOPKINS, in charge of forest insect investigations.
W. T). 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.


TRUCK CROP AND STORED PRODUCT INSECT INVESTIGATIONS.
F. H. CHITTENDEN, in charge.
I1. M. RUSSELL, C. H. POPENOE, D. K. MCMILLAN, E. G. SMYTH, THOSE. H. JONES,
M. M. HIGH, FRED. A. JOHNSTON, agents and experts.
I. J. CONDIT, W M. B. PARKER, collaborators in California.
II. 0.1MARSH, collaborator in Hawuaii.
[Cir. 130'
II










United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.
L. 0. HOWARD, Entomologist and Chief of Bureau.


THE OAK PRUNER.a
(Elaphidion nillosinm Fab.)
By F. H. CHITTENDEN,
In Charge of Truck Crop anid Slor,'d Product Insect Investigations.

INTR(O)DUCTORY.

Many sorts of trees, particularly oak and hickory, grown for shade
are often noticed with their limbs severed as if with a knife or saw.
Underneath these trees numbers of twigs and small branches strew
the ground. The severed limbs are from a few inches to 2 or 3 feet
long, and on one occasion a limb was seen that measured 10 feet in
length and another that was 1 inches in thickness. Young trees are
sometimes felled. An examination of one end, sometimes of both
ends, of a severed limb will show a smoothly cut surface near the cen-
ter of 'which will be seen a more or less oval opening plugged with
fine shavings and sawdust (fig. 1, e,J).

DESCRIPTIVE.

If one of these limbs be split open at the proper time a soft-bodied
larva, resembling that shown in figure 1 at a, will be found. This is
the larva of the oak pruner. It is nearly cylindrical, soft and fleshy,
of a whitish or light yellowish color, and is provided with rudimentary
legs (fig. 1, g).
aFormnerly the species under consideration was known under two names, Elaphi-
dion villosiu, Fab. and E. paralllclln Newm. The writer, however, has seen an ablun-
dance of specimens of what are labeled by both names, and while it may be true that
there are two species it is certain that the species which breed in the North from
the amputated twigs are identical, since the writer has reared both what are known
as villosumi and paralldum from such twigs. That which breeds in the portion remain-
ing on the tree has not been investigated, but it is probably not different.
Horn believed the two species identical and his opinion should not be disputed
until the contrary can be proved.
65401-Cir. 130-10 1


Isued December 10, 1910.


CIRCULAR No. 130.






THE OAK PRUNER.


The beetle which produces this larva is slender and cylindrical,
dark brown, and clothed with grayish, somewhat mottled pubescence.
The antenna of the female are shorter, those of the male (illustrated
at b) longer, than the body; the proximal joints are armed with small
spines. Each elytron terminates in two small spines and the femora
or thighs are unarmed. The length of the body varies from about
one-half to three-fourths of an inch.
DISTRIBUTION. *
Available records show that tilhe typical oak pruner (Elaphidion
rillosum Fab.) occurs from New England westward to Michigan,
and probably farther west, and southward through the District of
Columbia and Virginia to North Carolina, while there are specimens
in the United States National Museum labeled Texas. It is there-
fore evident that the species covers the greater portion of the east-
ern United States,
with the possible ex-
Sception of Georgia
V. ..' Band one or two of
a the Gulf States,
"c, from which the typ-
ical form has not
been seen.


I'


C' FOOD PLANTS AND
INJURY.


.f The list of food
plants of this spe-
cies includes oak,
FIG. 1.-The oak pruner (Elaphidion rillosum): a, Larva; b, beetle; c, hickory, pecan,
pupa; d, end of twig cut. by larva from tree; e, reverse end contain- i
ing insect; f, same from side, split to show pupa within; g, leg of chestnut, maple, fir
lar, a a, b, c, About twice natural size; d, e, f, natural size; g, (Abies) (doubtful,
greallv enlarged. (Author's illustration.) recorded by Halde-
Iman ), l1 Cust, eliii, redbud (Cercis ca nadensis), apple, plum, peach, pear,
quince, grape, orange, Osage orange (Maclura aurantiaca), wistaria,
climbing bittersweet ('dastrus scandens), black walnut, sweet gum,
and hackberry, according to the records of the Forest Insect Investiga-
tions of this Bureau. Indlee(d, this insect or allied species will attack
alhimiost very forin of deciduous trees, shrubs, and vines with woody
stalks. Tl(he lpruIned twigs of various trees and slirut)s are of frequent
occurrence, and among those which have been noted by the writer
in the v'icillnity of the District of Columnbia and in New York are the
spiceIuish (Litndcra benzoi*), sassafras, sumac, English or white
walnut, and beech. Since no other species of insect in thle regions
[Cir. 130]






THE OAK PRUNER.


specified is known to have the same pruning habit, it is practically
certain that the species under discussion is the culprit.
Of injuries by this species, it has been reported that in 1886 "peachI
trees in portions of Michigan were seriously injured. The twigs were
cut off so as to nearly destroy some of the trees." In 1892 the ex-
traordinary abundance of this pruner in Pennsylvania, New Jersey,
and neighboring States attracted considerable attention. At that
time carloads of the branches could be gathered up from the ground
throughout the oak forests in Bucks County, Pa. One of the striking
features noticeable that year in riding through that part of the
country lying between Washington, D. C., and New York City was
the unusual amount of injury by Elaphidion on oaks. In some local-
ities every tree had several dead or dying twigs, and the ground
beneath was strewn with branches which had been damaged by this
species and later broken off by the wind.
In the writer's experience the oak pruner was extremely abundant
in years past in the neighborhood of Ithaca, N. Y., and near South
Woodstock, Conn., on the shagbark hickory, the severed twigs and
branches occurring by the barrelful under a single tree. In one
instance a pear orchard at Ithaca, N. Y., had been very extensively
pruned. The insect had apparently attacked healthy living twigs
and several trees had every appearance of having been killed outright.
A few of the injurious and other occurrences reported to this
Bureau during the past decade may be mentioned: Regarding sup-
posed damage to oak, Mr. R. A. Edwards, of Perut, Ind., wrote on
March 27, 1901, that lihe could not observe that the pruner did actual
damage beyond cutting off the smaller branches, some of which do
not reach the ground, but hang from the limb or lodge upon limbs
below and there die. September 5, 1902, Mr. Edlmund L. Tyler, of
Anniston, Ala., sent a limb of hickory nearly 5 feet. in length which
had been pruned 3 feet from the end by the oak pruner. The point at
which amputation had taken place was an even inch in diameter.
April 25, 1903, Mr. Albert M. Boozer, of Columbia, S. C., sent this
species, which he thought to be injurious to pecan in that vicinity.
It was probably merely concerned in more serious injury due to the
pecan twig-girdler (On cideres cingulata Say) and to branch and trunk
borers. Mr. E. J. Vann, of Madison, Fla., stated, in a letter dated
July 28, 1905, that what. he considered this species had almost ruined
dwarf chestnuts in that, vicinity. Miss Alice S. TIainsworth, of
South China, Me., wrote, July 30, 1906, that this species was destroy-
ing the beauty of oak trees in that vicinity. The lawn beneath the
oak trees was continually strewn with fallen branches. In 1907
report of injury to oak in South Carolina was received. During
1908 the depredations by this species were widespread and general,
[Cir. 130]






4 THE OAK PRUNER.

injury having been reported in Massachusetts, Pennsylvania, Vir-
ginia, and Kansas to oak, elm, pear, and wistaria. The year follow-
ing pecans were attacked in Alabama and Mississippi, and hickory
and oak in Illinois. In 1910 the oak pruner attracted widespread
attention in the States of New York, Connecticut, and Massachusetts
and became the subject of many newspaper notices under the name
of the "gun-worm."
LIFE HISTORY.

From present knowledge of this species the following brief account
of its life history may be giVen:
In the northern portion of the upper austral life zone the adult
appears in early summer. The mother beetle inserts an egg, usually
in one of the smaller twigs of a living tree. The young larva latching
therefrom first attacks the wood under the bark, following the grain
of the wood and packing its burrow with its sawdust-like castings.
The larva, as it grows, bores toward the base, often consuming the
wood entirely around the limb and ejecting its castings through
holes which it makes in the bark. Later it follows the axis of the
twig, boring through the center and excavating a more or less oval
channel, sometimes for a distance of several inches. Dr. Asa Fitch a
has said that the larva is only about half grown when it severs the
limb in which it is working, but it has more probably attained its
full growth at this time. lie described this operation, recounting
at length how, with "consummate skill and seemingly superterrestrial
intelligence, he varies his proceedings to meet the circumstances of
his situation in each particular case."
From Fitch's account it would seem that lie imputed to this insect
a reasoning power, which enables it to modify its operations according
to conditions and to judge just how far the limb should be cut off
to insure its ultimate anmpl)utation by the wind without endangering its
own safety. Whether guided(l by reason or by blind instinct, the
insect is actually enabled(l to accompll)lish this purpl)ose.
After cutting away thle wood in such manner that the winds will in
tillle )riillg the limb) t.o the ground, tlhe contained larva retreats into its
burrow and pluIgs u1) thle severely end with castings. Here it trans-
for,-s3 to Lpupa, (fig. 1, c, f), somietiiies late in the autunin and often
not until early spring, assuming tlie adult stage as early as November
n1111d apllearing a b)mad in June ainm throughout the summer until
Septeml1beI.
A larva received front South Woodstock, ('onn., transformed to
Iut)IL Maly 3 and to adult May 21, lhavitig thus )passed tlie pilpal stage
in eighteen days, tl1e avrage t 'mperaturc having irbeen about 74 F.
a lII'ni, ASA.- Fifth RTport ii I Ins1tcts New York, pp. 7417-804, 1859.
;rir. Emi]





THE OAK PRUNER.


Although this species normally completes it transformations in
amputated or fallen limbs, it occasionally breeds in limbs that have
not been severed. It does not always cut off the twigs in which it
lives, and the larva sometimes reverses the order of proceedings and
directs its burrow toward the distal end of the branch, which it cuts
off at the end of its burrow and remains in the branch attached to
the tree.
From the earlier accounts of Fitch and others it would be inferred
that the insect requires a single year only for the completion of its life
cycle. Dr. John Hamnilton,a however, has stated that ,a. longer period
is require(l, three years being the usual time, and in individual cases
four or more years ) being consumedl. The writer is strongly inclined
to believe such exceptionally long periods, even three years, to be the
result of un(lue dryness ca'iised by unnatural indoor conditions.

W'IlY TIlE LARVA AMPUTATES A LIMB.

The purpose of the larva in cutting away the wood furnishes an
interesting t,)op)ic for speculation. The object attained is its ultimate
fall to the ground.
Peck, wlho wrote of this species in 1819,b thought that the limb, if
lpermiitte(l to remain attached to the tree, would become too dry and
that a certain degree of iioisture was require(l for the development
of the insect, ailnl that tlhe limb was accord inlgly partially severed
that it mighllt eventually fll, and thbat then, lying on the ground amidi
the autumnn leaves ;and beneath the winter's snow, the requisite
degree of moisture was inspired. In this belief Fitch conmcurred.
Mr. Fre(derick (C'larkson, however, took issue with Fitlch, believing
that the main object of the larva is to obtain dea(lwood and to
pre-vent the flow f sap. here wv have two contrary views expressed-
one that the object is to obtain moisture, the other to prevent it.
Such an excess of moisture is is obtained on the ground under the
melting snow and the p)ools of water that, collect in winter under the
infested trees (coul( ha irdly be I a necessity in the life history of any
terrestrial animal. Tli, ease witli which these insects may be reared
from dry twigs indoors is conclusive proof to the contrary. Why they
should require more moisture than fifty or a hundred others that could
be named that have similar food habits and do not breed exclusively
in fallen limnlbs it would b)e difficult to explain. Again, that the small
flow of sap of oak or hickory could seriously interfere with develop-
ment would seem unreasonable when we consid(ler that these insects
a HAMILTON, JoHN.-Canadian Entomologist, vol. 19, pp. 141-145, 1887.
b PECK, \\ILLIAM D.-Mass. Agr. Repus. and Journ., vl. 5, pp. 307-313, Jan., 1819.
(Treated as Sfiih',ororis pulalor Peck. Not seen.)
[Cir. 1311]






6 THE OAK PRUNER.
i':i
are able to survive the immersion to which they are sometimes sub-
jected for many days together during thaws and rainy spells in winter.
Another explanation of the limb's amputation occurs to the writer.
Those who have reared beetles from hard wood can not have failed to
observe that the larva before transforming cuts through the wood
until it reaches the bark, which is left untouched and serves to protect
the insect from marauding birds or other enemies. When the beetle
develops it has only to gnaw its way through this thin layer of bark to
effect its exit. There are undoubtedly some wood borers which are
provided in the beetle state with mandibles sufficiently powerful to
enable them to penetrate hard wood (Monohammus, for example), but
the majority, among them Elaphidion, are not thus favored, and
would be utterly unable with their weaker boring organs to escape,
and would perish in their burrows had they not while larvae exca-
vated the necessary channel for their exit. These exit channels
usually run at an angle to the axis of the wood. Now, in the case of
our Elaphidion, which usually lives in a slender limb which it bores
longitudinally, there is no room to place a branching, transverse
channel; accordingly the larva severs the twig and when it becomes
a beetle it cuts its way through the plug of castings.
As to Fitch's claim that the larva varies its operations to suit the
different sizes of limbs, the average infested twig is of about the
thickness of one's finger, and it is probable that the larva commences
proceedings late in the season with the approach of cold weather
when it is about full grown and ready for hibernation. To cut off
the limb is a labor of some magnitude for so small a creature and may
require several days for coml)letion. It. has a limited amount of
energy, (being now towar(l tlie en(l of its active existence as a borer,
andl the cooler weather serves to repress this energy, which is sufficient
for cutting away all the ,()wood in a small twig, but is inadequate for a
larger one. Tlie wood of a large branch is harder, and the insect
ceases work, perhaps from exhaust ion or from cold, or because its
instinct impels it to cut a certain amount, and when that is accom-
plish 1)d to cease, its Nwork 1)(eill(g ended(('. At. the close of Illis narra-
tiNve Fitcll says, in spite of a previous assertion that tle inllsect never
mi'c(l,'lcllates, that-
in al .i..l Ilirce-fitilrth.s (f th1e fallen limbs no worm is to 1e w fouli; and an exam-
iia ii,, n of hlmi .s11,ws Ithat Ihe insect perished at lie t ime the limb was severed
;i,1 6,.nr. it lhad cx'avated any burrow upward in its center, no1 perforaliin being
jln-'.s-ail .except t i.t 1 ,leadling intol tlie lateral twig. It is probable that in many instances
(In. liml, broke when the insect was i, tihe( a't of gnawing it. asunder, either from its
,owni weight ,r fro, i i l wi Id arising whilst tihe work was in progress.
(IClr. N:uJ






THE OAK PRUNER.


NATURAL ENEMIES.

As might be inferred from its manner of life, this insect enjoys
as nearly perfect exemption from predaceous or parasitic attack as
falls to the lot of most wood borers. Fitch, however, has stated
that some of our insect-eating birds destroy the larva, and the writer
has reared the parasite Bracon eurygaster Brulhe from twigs inhabited
by the species.
Among natural enemies of the oak pruner, Mr. F. H. Moshera
records the dlowny woodpecker (Dryobates putbescens), the blue jay
(Oyanocitta cristata), and the black-capped chickadee (Penthestes
atricapillus). Mr. W. L. McAtee, of the Bureau of Biological Sur-
vey, states that a species of Elaphidion is preyed upon by the downy
woodpecker and by the great-crested flycatcher (Mlyiarclms crinitus).
Mr. A. H. Kirkland a records having found a spider (Theridiumn tepi-
dariorum C. Koch) feeding upon the mature insects.

REMEDIES.

The pruning process is not always in itself especially injurious,
since when the pruner occurs in only moderate numbers the vitality
of the tree is not impaired. The ultimate effects, however, are likely
to be more serious. The fallen twigs serve as a breeding place for
hosts of other wood borers, many of which are injurious to shade
trees and to standing timber. Some of tllese do not hesitate, in
default of an abundance of deal or injured wood, to attack and
damage apparently healthy living trees.
In case this species becomes injuriously abundant, it may be readily
controlled by gathering the pruned twigs and burning them. This
should be done from time to time, as otherwise they accumulate and
make the lawn unsightly. To make this remedy of any value, the
coopl)eration of neighbors -is desirable. The work should be as
thorough as 1))ssible. If the twigs are gathered in numbers during
one season, the chances are that tlhe insects will not be nearly so
abundant thie year following.
Approved:
JAMES WILSON-,
Secretary qof Agriculture.
WASHINGTON, D. C., October 14, 1910.
a Forty-fifth Annual Rep. Sec. Mafs. State Board Agr. for 1897 (1898), p. 244.
[Cir. 130]





















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