152 STATES OF INSECTS. (Larva.) 
ing from two tubercles on the back of the eighth segment 
of the ferocious larva of that beautiful tiger-beetle, the 
Cicindela campestris L., not uncommon on warm sunny 
banks. This animal with incessant labour, as we are in- 
formed by M. Desmarets, digs a cylindrical burrow, to 
the enormous depth, the size of the animal considered, 
of eighteen inches. To effect this, it carries out small 
masses of earth upon its large concave head ; and having 
often occasion to rest in ascending this height, by means 
of these hooks* it fixes itself to the sides of its burrow, 
and, having finally arrived at its mouth, casts off its 
burthen. When these insects lie in wait for their prey, 
their head, probably in conjunction with the first segment 
of the body, accurately stops the mouth of the burrow, 
so as to form an exact level with the surrounding soil ; 
and thus careless insects, walking over it without per- 
ceiving the snare, are seized ina moment and devoured °. 
Another kind of appendage, which is found in some 
larvee, is the organ employed by them to carry the excre- 
ment; with which, instead of letting it fall to the ground, 
they form a kind of umbrella to shelter and probably con- 
ceal them. All the tortoise-beetles (Cassida) have in- 
struments for this purpose, as well as an Indian genus 
(Imatidium) very nearly related to them. ‘This in- 
strument is a kind of fork, half as long as the body, con- 
sisting of two branches, growing gradually smaller from 
the base to the summit, where they terminate in a very 
fine point, of a substance rather horny, and attached to 
the body near the anal orifice. They are armed on the 
outside with short spines, from the base for about a third 
of their length. When this fork, as it usually is, is laid 
* Prare XVII. Fie. 13. c. ® N, Dict. d Hist. Nat. vii. 95. 
