SB

94-5

Injuries to Forests and
Forest Products by
Roundheaded Borers.
J.L.Webb

IRLF

SB bfl

Y. B. Separate 542.

JURIES TO FORESTS AND FOREST PRODUCTS
BY ROUNDHEADED BORERS.

J. L. WEBB,

Agent and Expert, Forest Insect Investigations, Bureau of Entomology.

[FROM YEARBOOK OF DEPARTMENT OF AGRICULTURE FOR 1910.]

97236°— 11

CONTENTS.

Page.

Forest insect depredations 341

Roundheaded borers 341

Economic importance 342

Character of work 342

Life history and habits 342

Seasonal history 344

The western larch bark-borer 344

The southern pine sawyer 346

The locust borer 347

The painted hickory borer 349

The black-horned pine-borer 350

The cedar-tree borer 351

The western cedar bark-borer 352

The banded ash borer 353

The red-headed clytus 354

The oak pruner 355

The hickory twig-girdler 356

Summary . 357

Main Lib,

ILLUSTRATIONS.

PLATE.

Page.

PLATE XXIII. Work of the black-horned pine-borer (Callidium antennatum] . 348

TEXT FIGURES.

FIG. 19. — Work of the western larch bark-borer (Tetropium velutinum) 343

20. — Work of the western larch bark-borer ( Tetropium velutinum) 345

21. — Work of the southern pine sawyer (Monohammus titillator) 346

22. — Work of the locust borer ( Cyllene robinise) 347

23. — Work of the painted hickory borer ( Cyllene caryse) 349

24. — Work of the cedar- tree borer ( Hylotrupes ligneus) 351

25. — Work of the western cedar bark-borer (Hylotrupes amethystinus) 352

26. — Work of the banded ash borer ( Neodytus caprxa) 353

27. — Work of the red-headed clytus (Neodytus erythrocephalus) 354

28. — Work of the oak pruner ( Elaphidion villosum) 355

29. — Work of the hickory twig-girdler ( Oncideres cingulata} 356

ii

INJURIES TO FORESTS AND FOREST PRODUCTS BY
ROUNDHEADED BORERS.

By J. L. WEBB,
Agent and Expert, Forest Insect Investigations, Bureau of Entomology.

FOREST INSECT DEPREDATIONS.

In recent years much stress has been laid upon the conservation of
natural resources in the United States. Of these resources, the forests
have probably absorbed more attention than any other. Vast areas
have been set aside from the public domain as National Forests in
order that the timber supply of the county shall not become ex-
hausted. Much has been said on the subject of damage by fire to the
forests, and it is fully realized that this is an ever-present danger.
But a more insidious and equally relentless foe of the forests is found
in the form of insects which work terrible destruction, often unno-
ticed until the damage is done. The immense destruction to living
forests by certain scolytid barkbeetles, as well as the injurious work
of flat-headed borers, have been given attention in former Yearbook
articles. In this article another group containing many injurious
species is discussed, namely, roundheaded borers. The information
conveyed in this paper is based almost entirely on the material and
records of the forest insect collection of the Bureau of Entomology.

ROUNDHEADED BORERS.

Eoundheaded borers are so called to distinguish them from the
flat-headed borers.1 The general appearance is that of an elongate,
fleshy, yellowish-white grub, sometimes bearing three pairs of legs
and sometimes without legs. The head is more or less oval in shape,
though sometimes elongate, and often deeply retracted within the
lirst prothoracic segment, which is situated immediately behind the
head. The head is provided with a strong pair of jaws or mandibles,
brown or black in color, for cutting through plant tissue. Some spe-
cies mine only in the bark of trees, some mine in both bark and
wood, and some confine themselves to herbaceous plants. In each
case the borer is hatched from an egg laid upon or in the bark or

1 See " Injuries to forest trees by flat-headed borers," Yearbook, 1909, p. 399.

341

342 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

wood by the parent beetle. It lives and feeds entirely within the
bark or wood until it attains its full growth, when it changes to the
pupa, or resting stage, within its burrow. The pupa later transforms
to a beetle, which emerges and flies in search of suitable places to
repeat the process of propagating the species. In nearly every in-
stance the entire damage is done while the insect is in the grub, or
borer, stage. This form is therefore the most important from an eco-
nomic standpoint.

ECONOMIC IMPORTANCE.

Some species of roundheaded borers kill trees outright by mining
in the bark, thus destroying the vitality of the tree, while others
injure the wood of dead, dying, or felled trees, or timbers manufac-
tured from such trees. Still others both kill the trees and injure the
wood for commercial purposes. The annual loss to owners of forest
trees and forest products from this source, if figured up in dollars
and cents, would amount to a sum far in excess of what the ordinary
individual would think possible.

CHARACTER OF WORK.

The work of this class of insects usually appears as irregular wind-
ing mines or " wormholes " in the bark and wood. The mine always
starts in the bark, where the minute larva just hatched from the egg
starts to bore and feed. At first the mine is very small, but gradually
becomes larger as the borer advances and grows in size. As already
indicated, the work of some species is confined entirely to the bark.
The work of other species is found in both bark and wood. In this case
the mine is continuous from bark to wood, the entrance into the wood
being a flattened oval hole. That part of the mine which is in the
wood may be long or short, according to the species. In general it is
more or less winding and irregular, contains borings and woody excre-
ment, and finally broadens out into a cell or " pupal chamber." At the
farther end of this cell the mine, or " exit burrow " as it now becomes,
usually leads directly to the surface by the shortest route. Upon the
surface it usually appears as a perfectly round " exit hole " (fig. 21, d).

LIFE HISTORY AND HABITS.

As a usual thing the adult female beetle lays an egg or a cluster of
eggs either in or upon the bark in the spring, summer, or early fall.
Sometimes the parent female excavates a pit in the bark with her
mandibles, through which the eggs are thrust by means of the ovi-
positor. In other cases eggs may be deposited in crevices of the bark
or under the overlapping scales of bark. In a few days after the egg is

INJURIES BY ROUNDHEADED BORERS.

343

deposited a minute wormlike larva (fig. 19, c) issues therefrom and
immediately begins boring into the bark with which it finds itself in
contact. The larva usually proceeds directly to the inner bark, or
cambium, immediately next to the wood. Here the larva mines and
feeds until it reaches a certain growth, when it makes preparation for
a change called pupation. The entire growth of the insect is attained
in the larval form.
Usually, before it at-
tains full growth, how-
ever, the larva mines
either into the solid
wood or into the outer
corky bark and digs out
an elongate oval cell,
in which it will soon
pupate. From the far-
ther end of the pupal
cell the larva, as a gen-
eral thing, extends the
mine almost to the sur-
face of the tree or log,
in order to facilitate its
emergence into the open
air when it has gone
through its changes in
the pupal cell to the
adult or beetle form.
This work completed, it
retires to the pupal cell
and awaits the change
to the pupal form.
Finally the outer skin
comes off and the insect
lias an entirely different
form and appearance
(fig- 20, d). It is now
a pupa. The length of
time passed in this form
is variable with the
species and with the local conditions, the pupa resting perfectly
quiescent in its cell during this period. At length another change
takes place and the insect is in the adult or beetle stage (fig. 20, 5).
At first the beetle retains the white color of the pupa and ^arva, and
the outer tissue of the body is quite soft. But gradually the color
turns darker and the outer tissue becomes hard and chitinous. When

FIG. 19. — Work of the western larch bark-borer (Te-
tropium velutinum). Sections of bark of western
larch : a, Cluster of eggs deposited under overlap-
ping scale of outer bark, the overlapping scale, in
this instance, having been removed ; 6, inner surface
of bark with newly started mines ; c, small larva, a
few days old. Slightly enlarged. (Original.)

344 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

fully hardened and mature the young beetle crawls into the mine
leading away from the pupal cell and completes this mine to the sur-
face of the tree or log. It then flies away. Mating and egg laying
soon follow to provide for another generation.

SEASONAL, HISTORY.

Probably in the great majority of cases the larva does not change
to the pupa until the spring following the season in which the egg
is laid, passing the winter either in the larval mine or in the pupal
cell. However, pupation may take place in the fall and the winter
be passed in this stage, or the adult stage may be reached in the fall
and the winter be passed in this form within the pupal cell. The
following spring the larvae which have wintered over transform to
pupae. The pupae soon transform to adults and the adults emerge
and take flight. Likewise, the pupae which have wintered over trans-
form to adults and emerge. The first to emerge, however, are those
individuals which have wintered over as adults. Sometimes a spe-
cies may have two generations a year, or a partial second genera-
tion. In these cases development takes place rapidly after the eggs
are laid in the spring, the adult insects of the first generation emerg-
ing in late summer or fall, and laying eggs for the second generation.
The second generation passes the winter as outlined above. In still
other and more rare cases two or more years may be necessary for the
complete development of certain species.

THE WESTERN LARCH BARK-BORER.

(Tetropium velutinum Lee.)

At the present time the western larch bark-borer is quite a serious
pest in the Glacier National Park in Montana. In the vicinity of
Lake McDonald about 10 per cent of the stand of western larch or
tamarack is being killed annually by this bark-borer. Besides larch
it attacks fir, Douglas fir, western hemlock, and pine, in the Rocky
Mountain and Pacific coast regions.

The eggs are deposited in clusters under overlapping scales of bark
(fig. 19, a) and the minute larvae hatching therefrom proceed to the
inner bark, where they immediately commence their mines (fig. 19, &).

The work of this borer in larch is confined to the bark, though in
some of the other host trees mentioned above it sometimes enters the
sapwood. The larval mine is irregular and winding in the inner
bark. The number of mines is so great as to completely girdle the
tree and cut off the sap, thereby causing the death of the tree. Often
almost the entire inner layer of bark, or cambium, is destroyed for
quite a considerable space upon the trunk (fig. 20. a).

INJURIES BY ROUNDHEADED BORERS.

345

The grub (fig. 20, c) is elongate and somewhat cylindrical, yellowish
white in color, and about 1 inch long when full grown. Its mouth-
parts are dark brown to black, and the under side of the body is pro-
vided with three pairs of minute legs. It lives in the bark about a
year, emerging in the spring or summer as an elongate, brownish
to black beetle (iig.
20, 6), the surface of
the body having a
velvety appearance.
The beetle ranges in
length from 9 to 19
mm.1 The principal
time of emergence is
May and June. This
species attacks either
healthy, injured, or
felled trees.

The methods of
control are preven-
tive. Once a tree is
badly infested noth-
ing can be done to
save that particular
tree. Something can
be done, however, to
stop the spread of
the infestation to
other trees. Infested
trees should be felled
and barked and the
bark burned before
May 15. Something
could also be accom-
plished by the use of
trap trees. As the
insect breeds readily
in felled trees, a few
healthy trees felled in May or June near those infested would attract
the beetles which would otherwise deposit their eggs in healthy trees.
Later in the season, or before the following spring, the bark should
be stripped off the trap trees and burned.

a

FIG. 20. — Work of the western larch bark-borer (Tetropium
velutinum). Section of bark of western larch: a, Com-
pleted larval mines in inner bark ; 6, adult beetle ; c,
larva ; d, pupa. Insects approximately natural
(Original.)

size.

1 1 mm. =5^ inch.

346 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

THE SOUTHERN PINE SAWYER.
(Monahammus titillator Fab.)

Within recent years the States of the extreme south have suffered
severely from cyclones and other windstorms. An immense amount
of pine timber has been felled by these storms. In practically every
case great damage has been done to the fallen timber by the southern
pine sawyer over the entire area covered by the storm. It has been
estimated that during the years 1906, 1907, and 1908 the pecuniary
loss from this source in the Southern States was over $

FIG. 21. — Work of the southern pine sawyer (Monohammus titillator). Section of
trunk of storm-felled longleaf pine, showing : a, Egg pit in bark ; 6, entrance hole of
larva into wood ; c, pupal cell ; d, emergence hole ; e, g, h, sections of larval mines ;
f, scored surface of wood, scoring done by larva preparatory to entering wood ; i, larva ;
/, adult. Insect one-half natural size. (Original.)

This insect never attacks healthy trees, but only those already
dead, dying, or felled. The damage to each tree or log is the work
of the larvae or grubs which, after first mining in the bark, mine in and
through the sapwood, and even penetrate the heartwood, making large
unsightly holes (see fig. 21) which cause the lumber made from this
portion of the log to be thrown into the lowest grade, known to the
lumberman as " No. 2 common." The larva is an elongate, footless,
white grub (see fig. 21, i). The size varies considerably in different

1 U. S. Dept. of Agriculture, Bureau of Entomology, Bui. 58, Part IV, p. 45.

INJURIES BY KOUNDHEADED BOREKfcf.

347

individuals and according to age. The largest at maturity have been
found to measure slightly over 60 mm. in length and 9 mm. in
breadth at the broadest point. It appears
that normally there is one generation of this
species per year, with a partial second genera-
tion. Thus, a few larvae hatched from eggs
deposited in the spring go through their
changes to the adult form and the adults
emerge in the fall, while the larger number
of the larvae hatched from eggs deposited in
the spring and summer hold over until the
following spring, when the adults emerge.
The adult (fig. 21, j) is an elongate beetle
varying from 16 to 31.5 mm. in length and
from 5 to 10 mm. in width. The color is a
mottled gray and brown. In the male the
antennae ("horns") are very long, often be-
ing two or three times the length of the
beetle. In the female they are much shorter.
The principal time of emergence in the
Southern States seems to be March and
April.

Injury to felled pine timber by this species
may be prevented in two ways. First, by
placing infested logs in water while the
larvae are still in the bark and before they
have entered the wood; and second, by re-
moving the bark from the logs before the
larvae have entered the wood.

Trees or logs infested by this borer can be
readily recognized by the pits (fig. 21, a) ex-
cavated in the bark by the female prepara-
tory to depositing eggs.

THE LOCUST BORER.

(Cyllene robinicc Forst.)

FIG. 22.— Work of the lo-
cust borer (Cyllene ro-
Mniw). Section of trunk
of dying locust, showing
larval mines : a, Larva ;
6, adult. Insects natural
size. (Original.)

So important and destructive an enemy of
the black or yellow locust has the locust borer
become that in certain sections of the country
the growing of these trees has been considered
unprofitable because of the widespread depredations of the borer.
Throughout the Eastern and Middle States scarcely a community
where locust triees occur is exempt from this insect. Many trees are
97236°— 11 2

348 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

killed outright, and in others the wood is generally reduced in value
for commercial purposes.

So far as known, this species confines itself to the black or yellow
locust. The borer is an elongate, compact, yellowish-white grub or
larva furnished with three pairs of minute legs (fig. 22, a). Its
first work is done in the inner bark, where it destroys a portion of the
vital tissues. Later it enters the wood to feed and pupate. It is
here that its most destructive work is done, either by so honeycombing
the wood as to cause the death of branches or small trees or by
injuring the wrood for commercial purposes (fig. 22). The egg from
which the borer is hatched is deposited by the adult female in a
crevice of bark on the trunk or a branch, between the middle of
August and the middle of October. The larva passes the winter in
the bark, where it lies dormant in a hibernating cell of its own
construction. In the spring (usually about the second week in April
in the vicinity of Washington) activity commences again and the
borer leaves the hibernating cell to feed on the inner bark and outer
wood. In from two weeks to a month it enters the wood, where
it continues to feed and later changes successively to pupa and adult
(fig. 22, b). Adults begin emerging from the trees in August and
continue emerging till the last of September, the principal period of
emergence being the last half of August and first half of September.
The adult is an elongate beetle, the ground color of which is black,
with numerous cross-bands of yellow. Within a few hours after
emergence copulation takes place and the females begin depositing
eggs. There is but one generation a year.

The adults are usually common, feeding on the flowers of goldenrod
while this plant is in bloom.

When infested trees are so badly damaged as to be worthless they
should be cut down in May and June and burned to kill the broods
of larvae. At this time all such trees can be easily recognized by the
boring dust which is thrown out by the larvas and lodges in forks of
trees, in crevices of bark, and on the ground underneath. They can
also be recognized by the fading leaves, broken branches, etc. This
work should be completed by the time the flowers have all fallen from
the trees, or before the earliest varieties of goldenrod begin to show
evidences of flowering.

Hibernating larvaB may be killed by spraying the trunks and
branches with a strong solution of kerosene emulsion. This method
is specially recommended for the protection of small plantations,
groves, or shade trees. The work should be done in the fall or winter,
not earlier than November 1 and not later than April 1.

Great care should be exercised as to the time of year when locust
trees are cut for any purpose in order that the hibernating borers may
be destroyed. Except for the purpose of destroying the borers in the

Yearbook U. S. Dept. of Agriculture, 1910.

PLATE XXIII.

CZ--

WORK OF THE BLACK-HORNED PlNE BORER (CALLIDIUM
ANTENNATUM).

[Section of spruce rustic work, showing larval mines on surface
of wood, a, Entrance hole of larva into wood. (Original.)]

INJURIES BY KUUJNDHiiAD^D

wood, cutting should always be done between the 1st of October and
the 1st of April and the bark removed, and the tops and thinnings
burned. When it is necessary to
cut trees between the 1st of May
and the middle of September,
the tops should be burned and
the logs either barked, or sub-
merged in water for a few days
before they are shipped or
manufactured.1

THE PAINTED HICKORY BORER.

(Cyllene caryce Galian.2)

The painted hickory borer is
a close relative of the locust
borer and one of the commonest
and most destructive borers in
dead and dying hickory, the
larval mines often riddling the
sapwood and sometimes the
heartwood as well. Besides
hickory, it attacks walnut,
honey locust, mulberry, and
Osage orange, but never attacks
the black locust. Its range ap-
pears to be coextensive with that
of hickory.

The larva is a creamy white,
compact grub and has three
pairs of legs. The adult so
closely resembles the adult of
the locust borer (fig. 22, b) as
to be, to the ordinary eye, indis-
tinguishable from it. The sea-
sonal history, however, is quite
different from that of the locust
borer. The adults fly and de-
posit eggs in May and June and
do not appear at other seasons
of the year. The egg is laid in a
crevice of bark, and the young larva hatching therefrom proceeds to
the inner bark and soon enters the wood. If a great number of larvae

1 See U. S. "Dept. of Agriculture, Bureau of Entomology, Bui. 58, Part I, and Bui. 58,
Part III.

2 Known for many years under the name of Cyllene pictus Drury.

FIG. 23. — Work of the painted hickory borer
(Cyllene caryw). Section of hickory log
showing larval mines. (Original.)

350 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

are present in the same piece of wood, the solid wood is often literally
honeycombed with their mines (fig. 23). Pupation takes place in the
wood and the adult beetle usually emerges in May or June of the
year following that in which the egg is laid.

It has been found that hickory cut between August 10 and No-
vember 1 usually is not damaged by this borer. Therefore, where
much damage occurs from this source, all cutting of green timber
should be done as nearly as possible within this period. If it is
absolutely necessary to do the cutting in the spring or early sum-
mer, the bark should be removed and the tops and useless branches
burned.

THE BLACK-HORNED PINE-BORER.

(Callidium antennatum Newm. )

Injuries by the black-horned pine-borer to the bark or sapwood of
dead or dying cedar, juniper, pine, and spruce are common generally
over the United States. Often the timbers in rustic houses are found
to be infested, and rustic work is especially liable to injury, since the
presence of bark is absolutely necessary for the early development of
the borer.

When first hatched from the egg the larva feeds exclusively on the
inner bark, making an irregular winding mine. Later it also grooves
the surface of the wood (PI. XXIII) in making its mine, thus com-
pletely separating the bark from the wood, causing it to become loose
and, in many cases, to fall off. As the essential part of rustic work
is the bark, this sort of injury to it is quite a serious matter. The
larva is an elongate, fleshy, yellowish-white grub, usually about a
half inch in length when full grown. After working in the bark
until a certain period of development is reached, the larvae enter the
wood and continue their mines there. Usually they do not go deeper
than the sapwood, except in small stems or branches, where they
may penetrate the heartwood. The larva pupates in the wood. The
adult which finally emerges is a medium-sized, robust beetle, 9 to 14
mm. in length, blue to green in color throughout. There appears to
be but one generation a year. Adults fly and deposit eggs during
the months of April, May, June, and July. The winter is prob-
ably passed in the larval stage, the adults emerging the following
spring.

As a preventive against injuries by this borer, cedar, juniper, pine,
and spruce should be cut in the late summer, fall, or early winter.
If cut during the period between January and August, the trees
should be barked when felled. In the case of rustic work already in
use when found to be infested, some relief may be secured by inject-
ing bisulphid of carbon into holes in the bark through which sawdust-

INJURIES BY ROUNDHEADED BORERS.

351

like borings fall out, and stopping up the holes with putty or some
kind of wax. The dropping of the sawdust-like borings from the
logs or timbers always indicates the presence of this or a similar kind
of borer.

THE CEDAR-TREE BORER.

(Hylotrupes ligneus Fab.)

The cedar-tree borer attacks dead and injured Douglas fir, arbor-
vitse, red cedar, redwood, western hemlock, Engelmann spruce, juni-
per, alpine fir, giant arborvitae,
white fir, bigtree, and Arizona
cypress. In some cases living,
healthy trees may be attacked
and killed, and in other cases
the death and decay of already
unhealthy trees may be hastened
by this borer. This species also
seriously injures the wood of
felled trees for commercial pur-
poses and the bark and wood of
those used for rustic work. Its
occurrence is general over the
United States where its host
plants occur.

The larva (fig. 24, b) is a yel-
lowish-white grub about half an
inch in length when mature,
tapering from the prothoracic
segment to the last three ab-
dominal segments, which are
slightly larger than those imme-
diately preceding. The adult
(fig. 24, a) is a beetle varying
from 7 to 16 mm. in length.
The elytra or wing covers are
sometimes marked with alter-
nate transverse bands of red and
black, and sometimes are entirely
black or reddish brown. Apparently there is but one generation
a year. The egg is laid in crevices of the bark in spring or sum-
mer. The larva hatching from the egg excavates a winding, irregu-
lar mine in the inner bark, scoring the wood, later entering the
sapwood, and sometimes penetrating to the heartwood (fig. 24).
Pupation usually takes place in the sapwood, but sometimes occurs

FIG. 24. — Work of the cedar-tree borer
(Hylotrupes ligneus). Section of Ari-
zona cypress showing larval mines, a,
Adult ; &, larva. Insects natural size.
(Original.)

352

YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

in the heartwood or even in the bark. It appears probable that
the winter may be passed either in the larval, pupal, or adult stage,
the larval stage evidently predominating. The period during which
adults emerge is fyuite extended, apparently from March to Septem-
ber, inclusive, depending considerably on latitude and altitude and
on the stage of development reached before hibernation began during
the previous winter. The same period represents the time when eggs

are deposited for another gen-
eration.

The usual preventive measures
are recommended, i. e.. remov-
ing the bark from trees when
felled or treating rustic work
as recommended for the black-
horned pine borer, except those
felled in late fall or early winter,
which should not be injured by
this borer.

THE AVESTERN CEDAR BARK-BORER.

(Hylotrupes ametliy 'stiiuis Lee.)

The western cedar bark-borer
is a relative of the preceding,
the cedar-tree borer. Unlike the
latter, however, its range is con-
siderably restricted. The rec-
ords of the branch of forest in-
sect investigations, Bureau of
Entomology, indicate that it is
found only in the Pacific Coast
States. It is of considerable eco-
nomic importance, however, in
injuring the bark and wood of
recently felled giant arborvita?
and incense cedar.

The larva (fig. 25, a) is a
large, fleshy, yellowish-white grub, provided with three pairs of
feet. The largest larvae are about 25 mm. long at maturity and
about 8 mm. in width at the broadest part of the body, the pro-
thorax. The adult (fig. 25, I) is a medium-sized to large, robust
beetle, 12 to 23 mm. in length. The prothorax is black to reddish
brown. The elytra, or wing-covers, are of a brilliant blue to vio-
let color. The larva? mine in the inner bark, making broad wind-

FIG. 25. — Work of the western cedar bark-
borer. (// ylolrupes ainethystinus). Sec-
tion of incense cedar log, showing larval
mines, a, Larva ; ft, adult ; c, entrance
hole of larva into wood. Insects slightly
reduced from natural size. (Original.)

INJURIES BY ROUNDHEADED BORERS.

353

ing galleries and scoring the surface of the sapwood, sometimes
almost entirely separating bark from wood. They finally enter the
wood, sometimes mining to the heartwood, where the mine becomes
longitudinal. Pupation takes place in either
bark or wood, but usually in heartwood. It
is probable that there is but one generation a
year and that adults emerge and deposit eggs
in July, August, and September.

The same recommendations for preventing
injury as those given for the cedar-tree borer
are applicable to this species..

THE BANDED AST! BORER.

ru Say.)

(Ncocli/tu$

Numerous complaints have been received
by the Bureau of Entomology regarding seri-
ous damage to ash lumber by the banded ash
borer and closely related species. Of all
species concerned, however, this is apparently
the most destructive, the larvse perforating
the sapwood with their mines (fig. 26) and
greatly depreciating its value, if not entirely
ruining it. Besides ash, the borer attacks and
lives in mesquite and, rarely, in white oak.

The larva is an elongate, footless, fleshy
white grub about an inch in length when
mature. The adult is an elongate beetle, 15
to 18 mm. in length. The ground-color is
black, with four yellowish-white bands on
the elytra or wing-covers and one on the
{interior border of the prothorax. The tips
of the elytra are yellowish white. The
female beetle deposits her eggs on the bark
of dy'mg or dead trees or logs. There is but
one generation a year. The adults usually
emerge and deposit eggs in March, April, or
May. The larva.1 mine in the bark and sap- FIG. 26. — Work of the banded
wood and pupate in the sapwood. ^T'^SS^S' .~

Ash trees cut in the summer, fall, or early log showing larval mines.
winter are less liable to attack from this

species than those cut in the spring, but even those cut in the fall are
sometimes attacked the following spring. The best way to prevent
injury to logs cut during the winter and spring, when the logs are

354

YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

not to be immediately sawed into lumber, is to remove the bark imme-
diately upon felling or betAveen the 1st of March and 1st of June.
Placing the logs in water after the larvae have hatched and before
they have entered the wood is also effective.

THE RED-HEADED CLYTUS.

crythroceplialus Fab.)

The red-headed clytus is a close relative of the banded ash borer
and does considerable damage to the wood of dead and dying ash, as

well as to a number of other trees. The
list of its host plants includes ash, horn-
beam, hickory, maple, sweet gum, chest-
nut, cypress, hackberry, black walnut.
dogwood, black oak. persimmon, peach,
locust, sassafras, holly, mesquite, Texas
redbud, pine, Kentuck}^ coffee tree.
lilac, honeysuckle, and grapevine.

The larva is a slender, white, footless
grub of varying length when mature.
the average length at this stage being,
perhaps, about 15 mm. The adult is ti
slender beetle, 6 to 16 mm. in length.
The head and prothorax are red. The
anterior part of the elytra is reddish,
shading into dark brown or black pos-
teriorly. The elytra bear four pairs of
yellow bands, the first pair being at the
extreme base. There is but one genera-
tion a year. It appears that eggs may
be laid anywhere from March to Sep-
tember. The adult female deposits the
egg in a crevice of bark on a dead or
dying tree or log. The young larva,
hatching from the egg, mines first in the

inner bark and later continues the mine in the sapwood, thus injuring
the wood for commercial purposes (fig. 27). Pupation takes place
in the sapwood. The adult emerges from the tree or log the follow-
ing spring or summer after the egg is laid. This species is common
from the District of Columbia to Ohio, and south to Texas.

The same preventive measures as those given for the banded ash
borer apply to this species except, it will be noted, that the egg-laying
period of this species is much longer than that of the banded ash

FIG. 27. — Work of the red-headed
clytus (Xeuclytus ei'i/tlircxepha-
1ns) Sections of hickory log
showing : a, Larval mines on sur-
face of wood ; 6, larval mines in
the wood ; c, entrance hole of
larva into wood. (Original.)

INJURIES BY ROUNDHEADED BORERS.

355

borer, so that there is scarcely any season of the year when trees may
be cut and left with bark on, without danger of being damaged by
this borer.

THE OAK PRUNEK.

(Elaphidion viUosum Fab.)

In the oak primer we have a species which attacks only twigs or
small branches on living and injured trees, causing them to break and
fall to the ground. If occurring in large numbers it is of consider-
able economic importance, in retarding
the growth of twigs and branches. Be-
sides oak. this species attacks sassafras,
black walnut, hackberry, sweet gum, hick-
ory, and maple. Its range extends from
Pennsylvania to South Carolina, and as
far west as New Mexico.

The larva (fig. 28,- a) is a very slender
white grub about one-half inch in length.
The adult is a slender, shining, brown
beetle (fig. 28, &), 11 to 16 mm. in length,
rather sparsely clothed with gray pubes-
cence, each elytron terminating in two
spines of about equal length. Adults fly
in March, April, May, and June, during
which time oviposition takes place upon
the twigs or branches.

The young larva, after hatching from
the egg, first mines in the inner bark,
then enters the wood and girdles the
twig or branch by boring around it sev-
eral times in the same place (fig. 28),
leaving the bark and usually some of the
wood intact. The larva then mines in

the center of the twig beyond the girdle. The twig is usually
broken off at the girdle by the wind and falls to the ground, carrying
the larva with it. Pupation takes place in the center of the twig.
There is apparently one generation a year, the adult usually emerging
in March, April, May, or June of the year following that in which
the egg is laid.

When this species occurs in large enough numbers to be injurious,
the fallen twigs and recently killed twigs still on the trees should be
gathered and burned in the fall in order to destroy the larvae and
pupse in them.

FIG. 28 — Work of the oak
primer (Elaphidion rillosum).
Oak branch which has hcen
pruned, showing larval mines.
a, Larva ; 6, adult. Insects
natural size. (Original.)

356

YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

THE HICKORY TWIG-GIRDLER.

(Oncidcrcs cingnlata Say.)

The work of the hickory twig-girdler, like that of the oak primer,
is confined to the twigs and branches, and is often quite injurious.
Only living trees are attacked. The list of host plants includes
hickory, basswood, poplar, dogwood, black
gum, elm, persimmon, and acacia. The range
of this species extends from the eastern United
States to Arkansas and Kansas.

The larva is a footless white grub about half
an inch or more in length when mature. The
abdominal segments, except the last two, bear
minute granules, both above and below. The
adult (fig. 29, a) is a stout beetle. 12 to 14 mm.
in length, dark gray to reddish brown in color.
The flight of the adults and the deposition of
eggs usually occur in August or September.
The adult female punctures the branch or twig
and deposits an egg in each puncture. She
then gnaws off the bark and outer wood at a
point on the branch below where the eggs are
laid, completely circling the limb and causing
that portion of it beyond the girdle to die (fig.
29). The eggs hatch and the larva?, after min-
ing in the inner bark (fig. 29, 6), bore to the
center of the branch, where pupation takes
place in the larval mine, little if any protective
device in the way of a pupal chamber being
made. Probably most of the infested twigs
and branches fall to the ground before the
larva? complete their development, though some
do nor. It has been found that in the infested
branches which do not fall the larvae seldom
complete their development to the adult stage
unless the branches are in a shaded position.
Likewise, few adults are produced from
branches which are freely exposed to the sun after falling. This
insect reaches its best development in shaded twigs or branches, or
those partially covered by leaves or vegetation. In North Carolina
the larvae begin to pupate about August 1 of the year following that
in which the eggs were laid, most of the adults probably emerging
in September. The winter is therefore passed in the larval state.

FIG. 29 — Work of the
hickory twig - girdler
(Oncideres cingulata) .
Acacia branch showing
girdle, and larval mines
in bark and outer wood.
Insect natural size.
(Original.)

INJURIES BY ROUNDHEADED BORERS. 357

The work of the insect is not confined to the large trees, but
straight young seedlings from 4 to 10 feet high are sometimes
attacked and the entire top taken off, resulting in the removal of
about 2 feet of the new growth, usually nearly two years' incre-
ment. The adult beetle apparently injures the smaller twigs by
feeding upon the bark without depositing eggs in them.

Where this species occurs in destructive numbers it is advisable
to collect and burn the pruned twigs and branches. This should be
done several times between October 1 and August 1 of the following
year — once just before the leaves fall, once early in the spring
before vegetation starts, and again in the summer during June or
July. The twigs which first fall are quite apt to be almost hidden
by fallen leaves and quite difficult to find in the spring.

SUMMARY.

Ill general, roundheaded borers are elongate, fleshy, yellowish-
white grubs, which hatch from eggs deposited by the parent beetles
in or upon the bark or wood of the host plant. The grubs finally
change to pupre and these in turn change to adults or beetles. The
young adults in time emerge from the host and deposit eggs in or
upon other host plants; and so the life cycle goes on. Usually there
is but one generation a year, but in some species there may be two
generations a year, and in other species it may take longer than a
year for a single generation to develop.

Great damage is done to living and felled trees, and to standing
dead trees, by this class of borers. In some cases the borers confine
themselves to the bark, while in others they enter the wood. The
remedy in each case depends upon the habits and character of work
of the species under consideration.

The western larch bark-borer attacks perfectly healthy western
larches, making winding, irregular galleries in the inner bark, thus
cutting off the flow of sap and killing the trees. The methods of
control are preventive. No attempt is made to save a tree which has
once become badly infested. After becoming infested, trees should
be felled and barked and the bark burned before the following
May 15. A few healthy trees felled in May or June, near those in-
fested, should attract the beetles which would otherwise deposit
eggs in healthy trees. Before the following spring the bark should
be stripped from these trap trees and burned.

The southern pine sawyer is very destructive to felled pine timber
in the Southern States, making large, unsightly holes in the sap-
wood and greatly reducing in value a considerable percentage of
each log infested. Injury by this species may be prevented in two
ways. First, by placing infested logs in water while the larvse are

358 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

still in the bark and before they have entered the wood ; and second.
by removing the bark from the logs before the larvse have entered
the wood.

The locust borer is a serious and destructive enemy of the black
or yellow locust. Its first work is in the inner bark. Later it enters
the wood, where its most destructive work is done, either by so honey-
combing the wood as to cause the death of branches or small trees,
or by injuring the wood for commercial purposes. Hibernating
larvae may be killed by spraying the trunks and branches with a
strong solution of kerosene emulsion. Except for the purpose of
destroying the borers in the wood, cutting should always be done
between October 1 and April 1, the bark removed, and the tops and
thinnings burned. When it is necessary to cut trees between May 1
and the middle of September the tops should be burned and the
logs either barked or submerged in water for a few days before they
are shipped or manufactured.

The painted hickory borer attacks dead and dying hickory, walnut,
honey locust, mulberry, and Osage orange, the larval mines often
riddling the sapwood and sometimes the heartwood as well. To pre-
vent the spread of this species, all cutting of green timber should
be done between August 10 and November 1. Timber which must
be cut in spring or early summer should have the bark removed and
the tops and useless branches burned.

The black-horned pine-borer is an enemy of dead or dying cedar,
juniper, pine, and spruce. Eustic work is specially liable to injury
from this source. As a preventive against injuries by this species,
cedar, juniper, pine, and spruce should be cut in late summer, fall,
or early winter. If cut between January and August the trees
should be barked when felled. In the case of injuries to rustic work,
an injection of bisulphid of carbon and the plugging up of the holes
with wax or putty is recommended.

-The cedar-tree borer attacks dead and injured Douglas fir, arbor -
vitse. red cedar. redAvood, western hemlock, Engelmann spruce, juni-
per, alpine fir, giant arborvita?, white fir, bigtree, and Arizona cypress.
Like the black-horned pine-borer, it is injurious to rustic work. The
usual preventive measures are recommended, i. e., removing the bark
from trees when felled, or treating rustic work as recommended for
the black-horned pine-borer.

Makers
Syracuse, N. Y.

PAT. JJN, 21. 1908

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