THE HICKORY BARK-BORER. 295 



female mostly for the purpose of laying her eggs. lu 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. 



" 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. US'), but afterwards lengthwise along the bark (Fig. 118^), 

 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 difliculty 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^) 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 larvse will be found reuaaining 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 Eiley, and Bracon scolytivorus Cresson. 



The beetle. — Male entirely black, or black with browu wing-covers ; the head above 

 flat, concave towards tip ; thorax very little longer than wide, and narrowing in 

 front but slightly. Elytra with abont 10 strise 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 larvse, 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.) 



