830 LEriDOTTERA. 



iind the edges of the aLdoininal segments are armed with 



transverse rows of short teeth. By means of these little 



teeth, the chrysalis, just before it is about to be transformed 



to a winged insect, works its way out of 



Fig. 158. O ' J ^ 



the cocoon, and partly through the hole, in 

 the stem or root, Avhich the caterpillar had 

 previously made ; and the shell of the chrys- 

 alis (Fig. 158) is left half emerging from the 

 orifice, after the moth has escaped from it. 

 The ash-tree suffers very much from the attacks of borers 

 of this kind, which perforate the bark and sap-wood of 

 tlie trunk from the roots upwards, and are also found in 

 all the branches of any considerable size. The trees thus 

 infested soon show symptoms of disease, in the death of 

 branches near the summit ; and, when tlie insects become 

 numerous, the trees no longer increase in size and height, 

 and premature decay and death ensue. These borers as- 

 sume the chrysalis form in the month of June, and the 

 chrysalids may be seen projecting half-way from the round 

 holes in the bark of the tree in this and the following 

 month, during which time their final transformation is ef- 

 fected, and they burst open and escape from the shells 

 of the chrysalis in the winged or moth state. Under this 

 form this insect was described, in my paper in Professor 

 Silliman's " Journal of Science,"' by the name of Troclii- 

 Uuni * denudatum ; as the habits of the larva are now 

 ascertained, we may call it the ash-tree Trocldlium. Its 

 general color is brown ; the edjies of the collar and of 

 the abdominal rings, the shins, the feet, and the under 

 side of the antennas are yellowish. The hind wings are 

 transparent; the fore wings are opaque and brown, varie- 

 gated with rust-red ; they have a transparent space near the 

 tips, and expand about an inch and a half. 



* The word Trochilium is derived from Trochilus, the scientific name of tlie 

 humming-bird genus; and these insects are sometimes called humming-bird 

 moths. 



