THE HICKORY BARK-BORER. 295 
female mostly for the purpose of laying her eggs. In thus entering 
the tree they bore slantingly and upward, and do not confine them- 
selves to the trunk, but penetrate the small branches and even the 
twigs. The entrance to the twig is usually made at the axil of a bud 
or leaf, and the channel often causes the leaf to wither and drop, or 
the twigs die or break off. 
a The female in depositing, confines herself to the trunk or larger 
limbs, placing her eggs each side of a vertical chamber, as described 
by Mr. Bryant.* Here she frequently dies, and her remains may be 
found long after her progeny have commenced working. The larvae 
bore their cylindrical channels, at first, transversely and diverging 
(Fig. 118 1 ), but afterwards lengthwise along the bark (Fig. 118 2 ), 
always crowding the widening burrows with their powdery excrement, 
which is of the same color as the bark. The full-grown larva (Fig. 118*), 
natural size and enlarged) is soft, yellowish and without traces of 
legs. The head is slightly darker, with brown jaws, and the stigmata 
so pale that they are with difficulty discerned. It remains torpid in 
the winter, and transforms to the pupa state about the end of the fol- 
lowing May. The pupa (Fig. 118 5 ) is smooth and unarmed, and shows 
no sexual differences. The perfect beetle issues through a hole made 
direct from the sap-wood, and a badly infested tree looks as though it 
had been peppered with No. 8 shot. The sexes differ widely from each 
other, the male having spines on the truncated portion of the abdomen, 
not possessed by the female. The eggs are deposited during the 
months of August and September, and the transformations are effected 
within one year, as no larvae will be found remaining in the tree the 
latter part of July. 
Two ichneumon parasites, according to Riley, prey upon this insect, 
and after killing the grub spin little pale cocoons. They are Spathius 
trifasciatus Riley, and Bracon scolytivorus Cresson. 
The beetle. — Male entirely black, or black with brown wing-covers ; the bead above 
flat, concave towards tip ; thorax very little longer than wide, and narrowing in 
front but slightly. Elytra with about 10 striae confused at the sides, but regular 
above, and composed of small, deep, approximate punctures; interstitial spaces with 
a single row of minute and nearly obsolete punctures ; The female differs in having 
the head rather shorter, more rounded, less hairy, and the venter unarmed. Length 
0.15--0.20 inch. (Riley.) 
*The mode of operation appears to be as follows: Boring through the bark, the in- 
sect forms a vertical chamber next to the wood, from half an inch to an inch in 
length, on each side of which it deposits its eggs, varying in number from twenty to 
forty or fifty in all. The larvae, when hatched, feed on the inner bark, each one fol- 
lowing a separate track, which is marked distinctly on the wood. Some trees con- 
tain them in such numbers that the bark is almost entirely separated from the wood. 
In many cases the upper part of the tree is killed a year or two before the lower part 
is attacked. (Riley's Fifth Annual Report Inj. Ins. Missouri, p. 104.) 
