172 INSECTA. 
feet, which correspond to the legs of the perfect Insect, and 
from four to ten additional membranous ones, the twe last of 
which are situated at the posterior extremity of the body, 
near the anus; those which have but ten or twelve in all, have 
been called, from their mode of progression, geometra. They 
cling to the plane of position with their squamous feet, and 
then elevating the intermediate segments of the body in the 
form of a ring or buckle, approximate the two hind feet to 
the preceding ones, disengage the latter, hold on with the 
last feet, and move their body forwards to recommence the 
same operation. . Several of these geometre, when at rest, 
remain fixed to the branches of plants by the hind feet alone, 
where,.in the form, colour and direction of their body they 
resemble a twig; they can support themselves in this position 
for a long time, without exhibiting the slightest symptom of 
life. So fatiguing an attitude must require prodigious muscu- 
lar foree, and in fact Lyonet counted four thousand and 
forty-one muscles in the caterpillar of the Cossus ligniperda. 
Some caterpillars with fourteen or sixteen feet, but of which 
some of the intermediate membranous ones are shorter than 
the others, have been called pseudo-geometre. ‘The mem- 
branous feet are frequently terminated by a more or less com- 
plete crown of little hooks. 
The body of these larve are. generally elongated, almost 
cylindrical, soft, variously coloured, sometimes naked, and 
sometimes covered with hairs, tubercles and spines. It is 
composed of twelve segments or annuli, exclusive of the head, 
with nine stigmata on each side. Their head is invested with 
a corneous or squamous dermis, and presents on each side 
six shining granules, which appear to be ocelli; it is also fur- 
nished with two very short and conical antenne, and a mouth 
composed of strong mandibles, two maxille, a labium and four 
small palpi. The silk they employ is elaborated in two long — 
and tortuous internal vessels, of which the attenuated supe- 
rior extremities terminate in the lip. A tubular and conical 
mammilla is the spindle through which the threads are spun. 
Most caterpillars feed on the leaves of plants; some gnaw 
