330 
LEPIDOPTERA. 
and the edo-es of the abdominal 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 
the cocoon, and partly through the hole, in 
the stem or root, which 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 
the 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 the 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 Trocld- 
lium * denudation ; as the habits of the larva are now 
ascertained, we may call it the ash-tree Trocldliwm. Its 
general color is brown ; the edges of the collar and of 
the abdominal rings, the shins, the feet, and the under 
side of the antennae 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 the 
humming-bird genus; and these insects arc sometimes called humming-bird 
moths. 
