THE HETEROMERA. 
241 
which are entire, and the thorax (except in Myderus), 
snbovate or cordiform, narrowed in front and behind, 
and often narrower at base than at apex ; the elytra 
are rounded at apex and cover the abdomen, which 
lias five free ventral segments ; the family may be 
divided into three tribes, the Pythina, Salpingina and 
Mycterina ; the first of these may be distinguished 
from the other two by the fact that the intermediate 
coxae have a very distinct trocliantin, as well as by the 
large depressed form ; and the Salpingina may be 
known from the Mycterina by the side pieces of the 
mesosternum not attaining the intermediate cox®, as 
well as by having the thorax much narrower 
at base than at apex, whereas in Mycterina it is 
broader. 
The Pythina comprise the single genus Pytho ; P. 
depressus, hitherto found only in Perthshire under fir- 
bark (where also occurs the larva, which has two strong 
hook-like projections on the upper side of the last seg- 
ment) is very depressed, metallic, usually blue or 
green, but sometimes nearly testaceous, and with two 
strong depressions on its thorax. Both the perfect 
insect and larva are carnivorous, feeding upon other 
subcortical species. 
The Salpingina, on account of some of their mem- 
bers possessing a rostrum, afford a passage to the next 
section, wherein such prolongation of the head is con- 
stant, and with which they have been associated by old 
authors. 
Their antenn® are thickened at the apex, the last 
joint of their maxillary palpi is not hatchet-shaped, 
their mandibles do not project beyond the labrum,and 
their body is smooth. 
R 
