16 MODERN CLASSIFICATION OF INSECTS. 



pores (spiracles or stigmata), varying in their number ; internally the 

 trachejE emit an infinite number of ramifications, extending to all parts 

 of the body like the branches of a tree, and thus oxyglnating the cir- 

 culatory fluid which is diffused from the series of hearts throughout 

 the various organs. 



The Muscles of insects are not unlike those of the higher animals, 

 beino- however attached to the inner surface of the external covering 

 of the animal, but being far more numerous than in the human body, 

 Lyonnet having discovered more than four thousand in the caterpillar 

 of the goat moth, whereas there are in man only 529 ; they are at- 

 tached to the various organs intended to be brought into motion by 

 their assistance, being either flexors or extensors, levators or depressors. 



Of the System of Generation it will be sufficient to observe, that in 

 insects the sexes are constantly distinct, each sex being provided with 

 its own peculiar generative organs ; those of the female consisting of 

 numerous ovaries and egg passages, and an ovipositor of varied con- 

 struction, and frequently external ; and that the impregnation of these 

 eggs is produced by the union of the sexes. It is also to be observed, 

 that amongst certain tribes of insects which are social in their habits, 

 and where a certain number of individuals are required to perform 

 the duties of the community distinct from those of reproduction, this 

 effect is produced by the peculiar nature of the food given to these 

 individuals whilst in the larva state, which has the extraordinary 

 effect of retarding the development of their generative organs; 

 moreover, there are other tribes (Aphides) in which a single impreg- 

 nation suffices for several subsequent generations. 



Shortly after impregnation, the female commences the laying of her 

 eggs, an operation not performed without the utmost solicitude on 

 the part of the parent for the welfare of her future offspring. The 

 various means adopted for the purpose of placing the eggs in such 

 situations as will ensure a due supply of food to the young when 

 hatched, are amongst the most extraordinary instances of instinct with 

 which we are acquainted. 



When the young insect first makes its escape from the eg^, it 

 appears in a form generally totally unlike that of its parent, although 

 in a few instances its form is that which it will retain through life. 

 It is now termed a caterpillar, grub, or maggot {larva), and has 

 a series of moultings to undergo, during the last two or three 

 of which its form is more or less altered. In the earlier stages 



