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as late as October 7. After that date they could not be found on the trees in the writer's experimental plot. They are sluggish, very inactive insects, and move with a slow, lumbering gait. When they are disturbed, either by being jarred or by any sudden noise, they do not fly but feign death and drop to the ground, the beak and the legs being closely drawn against the body. They remain quiescent usually for a minute or two before attempting to crawl away. When handled they emit a squeaking noise, produced by the rubbing together of parts of the body. Though close watch for it has been kept, flight has not been observed, and no one has recorded the beetles as spreading by means of flight. Whether or not they are incapable of flight the writer has not been able to determine.

Shortly after the beetles emerge from the pupal cells they begin to feed, selecting young, tender shoots. The bark is punctured by the beak, a round hole being formed down to the cambium layer, on which the beetles largely feed. The beetles are voracious feeders, and when they are abundant the young one-year-old shoots may be so completely riddled by the feeding punctures that they shrivel and die. So far as the writer's observations go, the beetles do not feed on old bark, but confine themselves to the young and succulent twigs. Punctures in old bark are for the deposition of eggs, and these always appear some weeks after the beetles have been feeding.

The beetles do not seem to migrate to any considerable distance. Although the wings are perfect and apparently suitable for flying, yet the beetles have never been observed in flight or attempting to fly. In the nursery it is not uncommon to find one block badly infested, whereas a block somewhat distant may be only slightly injured. Change of location in the growing of poplars from year to year frequently makes a marked difference in the degree of injury. One block of about 15,000 trees in a large nursery near Geneva had an infestation of nearly 50 per cent in 1915. A block of about the same number of trees situated threefourths of a mile distant showed in 1916 only a small infestation, 3.5 per cent, in the check rows. The beetles were abundant in 1915 in the block ready to be dug, and apparently they had confined their egg-laying operations to the poplars from which they had emerged. As this is true in all the cases coming under the writer's observation, it can readily be seen that a block ready to be dug, showing only a small percentage of infestation, may make an ideal center for distribution. As the nurseryman discards only severely injured stock, a block with such a low percentage of injury will practically have all the trees fit for sale, and in this way every egg deposited will be shipped away to start new infestations. When trees show considerable injury they are discarded and burned (fig. 113).

Although the beetles do not fly, yet they are undoubtedly well able to walk considerable distances. How far has not been determined, but they have been found a goodly distance from any of their food plants resting quietly on the trunks of various trees. This is especially true in the spring.

[graphic]

FIG. 113. A PILE OF DISCARDED CAROLINA POPLARS IN A NURSERY

Mating does not occur until ten days or more after emergence. This period is spent largely in feeding, and the beetles do considerable damage at this time to the vigorous growing shoots. Copulation occurs freely and a pair may remain several days in copula. Not only does mating last a considerable time, but it may be repeated again and again at different times.

Egg laying

Shortly after copulation the females seek out suitable places for the deposition of their eggs. They choose branches or parts of the trees more than a year old, and deposit their eggs in the corky parts of the bark. The eggs have never been found

in one-year-old stock, but only in wood two years old or older. Favorite places for egg laying are lenticels (figs. 114 and 115), scars, bases of branches, injured areas, or about the base of buds where the bark is somewhat thick. With her beak closely applied to such an area the female beetle at

once begins to eat into the bark. FIG. 114. Gradually she deepens the round hole

[graphic]

EGG PUNCTURES AT THE SIDES OF LENTICELS

until her entire beak is buried, up to the eyes. The time required for this operation varies from a few minutes to thirty or forty minutes. At the bottom of the hole the beetle may round out two or three small lateral cavities, or she may be content with only one. In the majority of

cases she does not dig out extra cavities, but uses the hole made for the deposition of but a single egg. When the cavity appears satisfactory, the beetle inserts her ovipositor and deposits from one to three or four eggs, depending on the kind of cavity dug. Then, reversing her position, she closely packs the eggs, both with beak and with antennæ, and covers them with fine pieces of the wood.

Egg laying continues from early August until October, but the number of eggs laid by a single female has not been ascertained. Whether or not, under New York conditions, all the females deposit all their eggs during this period, has not been finally determined. All American workers report that egg laying is finished in the autumn, and that the beetles do not hibernate but evidently die after the process is completed. In the

writer's work no hibernating adults were found in the spring in the nurseries, though it should be understood that no extended search was made for them. In the writer's experimental plot, adults which evidently had hibernated were taken on April 21, May 1, and June 6, 1916. One was fresh and clean, apparently having but recently emerged from its pupal chamber. Though these were observed, they may be only rare occurrences rather than represent a normal mode of hibernation. Furthermore, egg laying was not observed in the spring, and in the treated plots there was no evidence that any eggs were laid after application of the various treatments. Had egg laying in the spring been normal, certainly the treated plots would not have shown such a high percentage of control.

[graphic]

FIG. 115. EGG IN SITU, WITH OUTER

PART OF LENTICEL CUT AWAY

The egg

The egg when laid is pure white in color but it becomes pale cream when a few days old. The shell is very thin and fragile, somewhat viscous, and without any distinctive markings. The egg is oval in outline, measuring 1.1 by 0.8 millimeters. The shape varies considerably, since owing to the softness of the shell it is easily modified by the shape of the cavity in which the egg is laid.

The egg stage lasts from eighteen to about twenty-five days, depending largely on weather conditions. The first observation of eggs hatching out of doors was on October 2, 1916. Undoubtedly many had hatched

Early in

earlier, but from numerous examinations made during October the majority of the eggs had not hatched even as late as October 28. November, 1915, the eggs began hatching in great

numbers, and this continued until the latter part of the month.

[graphic]

The larva

When hatched, the young larva (fig. 116) is whitish in color and greatly resembles a miniature June-beetle grub except that the posterior end is the smaller and the larva is legless. It lies curled up in the egg cavity and begins at once to feed on the soft plant tissues. It is 1.5 millimeters in length, and 0.6 millimeter thick at its widest part. FIG. 116. YOUNG LARVA, It is regularly transversely wrinkled, but the skin.

FIG. 117.

JUST HATCHED

is nearly smooth except for scattering finehairs. The head and the mouth parts are light brown except the mandibles, which are dark brown with black tips. The larva is cylindrical in shape, gradually tapering toward the posterior extremity.

The larva feeds on the tender tissues of the plant and soon reaches the soft cambium layer. Externally the beginning of feeding can' be easily recognized by the blackish, wet frass that fills the outer part of the egg cavity. Feeding continues until cold weather, the early-hatching larvæ attaining a considerable growth.

In the spring feeding begins as soon as the weather has become sufficiently warm, usually the first week in April. Moist frass, black to brownish in color, is forced out of the burrow as the larva feeds ravenously. The direction of the larval channels is nearly always around the trunk or the branch, and the larvæ feed at first exclusively in the bark and the cambium layer. As a result the tree is frequently CHANNELS MADE BY girdled, especially if several larvæ are at work near the same place (fig. 117). The larval channels vary greatly in shape; some are

[graphic]

LARVE IN A YOUNG CARO

LINA POPLAR TREE

cylindrical and girdle the tree, others are flat, irregularly shaped chambers, while the majority zigzag in various directions through the cambium layer.

As the larvæ grow, the channels become larger and the amount of frass is greatly increased. In order to make room for the developing larva the frass is forced outside the channel, by small openings cut through the outer bark. This is well shown in figure 118.

[graphic]

FIG. 118. FRASS FORCED OUT
THROUGH SMALL OPENINGS

The larvæ become nearly full-grown before they leave the cambium layer. They then burrow at an angle upward into the hard wood of the tree. The beginning of this burrow is easily recognized, as the character and quantity of the frass suddenly changes. It becomes white and much larger in quantity, and consists of small particles of the wood cut off by

[graphic]

the mandibles of
the larva (fig.

119). In New
York the forma-
tion of the pupal
channel begins
about June 1.
By the middle of
June the majority
of the larvæ have
begun their pupal
burrows. At this
time, as one looks

down the rows of

[blocks in formation]

sawdust-like frass can be seen distinctly on the infested trees and on the ground beneath them.

In the formation of the pupal chamber the larva bores upward and into the heart of the small nursery trees. This burrow varies from slightly over an inch to several inches in

FRASS WHEN LARVA BEGINS TO BORE INTO HEARTWOOD ΤΟ FORM PUPAL CHAMBER

length. From three to four weeks are required FIG. 119. CHARACTER OF THE for its completion. When ready for pupation the burrow is solidly packed with frass, the pupal chamber being formed at the upper end (figs. 120 and 121). The larva then places itself head downward in preparation for pupation.

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