228 INSECTS. 



A crowd of insects both in the larva and perfect state are 

 found in the dung of animals ; and dead animal matter of all 

 kinds, particularly that of quadrupeds, birds, and fishes, is eager- 

 ly sought after by numerous species. The flesh-fly is well 

 known to deposite its ova in butcherVmeat exposed ; and the 

 feeding of these minute animals within the meat accelerates pu- 

 trefaction and dissolution. Even the ,dried flesh of animals, 

 and their skins preserved in museums, are the prey of small 

 Coleoptera of the genera Dermestes, Ptinus, &c. ; and these mi- 

 nute animals likewise destroy the most valuable furs. Other in- 

 sects attack living animals, and feed on their fluid and solid 

 parts. One larva in particular, belonging to the genus (Estrus, 

 lives on the back and under the skin of horned cattle, and feeds 

 on the pus which is formed by the tumours occasioned by their re- 

 sidence. Other larvae of the same genus are found in the stomach 

 of the horse, around the pylorus, and sometimes in the intes- 

 tines ; and sheep, horses, and oxen feed the larvae of another 

 species of (Estrus in their frontal sinus, on the fluid which ex- 

 udes from the nose. In short, no animal seems free from the 

 depredations of insects ; and some larvae live even in the inte- 

 rior of the bodies of other species, as the large family of the Ich- 

 neumons, the Cinips of Geoffrey, and the Sphex of Linnaeus. 



The organs of deglutition in insects present nothing very re- 

 markable. The oesophagus is a straight canal, passing between 

 the brain and the first nervous ganglion. It is surrounded by 

 the nervous matter which joins the two principal organs of sen- 

 sation. This part of the oesophagus is perhaps the seat of the 

 organ of taste. In the gnawing insects, the alimentary matters, 

 after having been cut and reduced to small portions by the ac- 

 tion of the mandibles, are carried to the pharynx. In the suck- 

 ers the nutritive fluids are carried there by the pressure of the 

 sucker. 



The organs of digestion comprise the stomach and intestinal 

 canal. These are, according to M. Marcel de Serres, formed 

 of three membranes. The stomach presents great variety in 

 point of form, and has been distinguished 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 in- 

 sects. In some it is simply membranous ; in others it is mus- 

 cular ; and in a third group it is not evident, that is, the oeso- 



