INSECTA. Sil 
lives on the back and under the skin of horned cattle, and feeds on the pus 
which is formed by the tumors occasioned by their residence. Other larvee 
uf the same genus are found in the stomach of the horse, around the pylorus, 
and sometimes in the intestines ; and sheep, horses, and oxen feed the larve 
of another species of estrus in their frontal sinuses,cn the fluid which 
exudes from the nose. In short, no animal seems free from the depreda- 
tions of insects; and some larve live even in the interior of the body of 
other species, as the large family of the ichneumons, the cinips of Geoffroy, 
and the sphex of Linneus. 
The organs of deglutition, in insects, present nothing very remarkable. 
The esophagus is a straight canal, passing between the brain and the first 
nervous ganglion. %t is surrounded by the nervous matter which joins the 
two principal organs of sensation. ‘This part of the esophagus is perhaps 
the seat of the organs of taste. In the gnawing insects, the alimentary 
matters, after having been cut and reduced to smull portions by the action 
of the mandibles, are carried to the pharynx. In the suckers, the nutritive 
fluids are carried there by the pressure of the sucker. 
The organs of digestion comprise the stomach and the intestinal canal. 
These are, according to M. Marcel de Serres, formed of three membrares. 
The stomach presents great variety in point of form, and has been distin- 
guished by Latreille, into three kinds, which he distinguishes as simple, 
double, and multiple. The stomach of the first form occurs in the greater 
part of the insects. In some it is simply membranous; in others it is mus- 
cular; and ina third group it is not evident, that is, the @sophagus is not 
dilated. Those which have the stomach membranous and dilated, live 
generally on the nectar of plants, such as the bees, butterflies, &c.; those in 
which the stomach is muscular, are chiefly the hemiptera ; and those in which 
this viscus is not dilated, feed commonly on leaves or roots, which they 
gnaw and eat. The insects which have a double stomach are the coleoptera 
which feed on living piey, such as the hydrocanthari, the cicindelete and the 
carabide. The greater part of the orthoptera are remarkable for the appa- 
rent multiplicity of their stomachs. The mole cricket of gardens has four. 
This insect and others analogous have been considered as raminating 
insects, or as having the faculty of returning again to their mouth the ali- 
ments in their organs of digestion. In insects, it is to be remarked, there 
often exist great differences in the structure of the intestinal canal, properly 
so called, in the state of larve, and in the perfect insect. Thus, in the 
caterpillar of the butterfly there is an @sophagus dilated abruptly to form a 
cylindrical stomach, with three transverse rows of coecums totally different 
from the form of the same parts in the perfect insect. Similar differences 
nave been observed in the larva of the bee, and indeed occur in many 
groups. ‘This change of structure is necessary for the accommodation of 
the animal to its changes of food; but when the larve and the perfect insect 
feed on the same materials, this alteration in organization does not take place. 
