104 FISHES DIAGRAM 5 



CLASS OF INSECTS 



DIAGRAM 6. 







GENERAL OBSERVATIONS. 



When we examine an insect, a cockchafer for instance, we at 

 once see that it is very different from the animals which we have 

 just been considering, such as the mammals, birds, reptiles, and 

 fishes. The insects, and all the animals which we have still to 

 notice, have no vertebrae or skeleton ; for this reason they have 

 been called mvertelrata ; that is, animals without vertebrae. But 

 among the invertebrate animals there are some, like insects and 

 Crustacea, which have a shell formed of rings which are more or 

 less hard , and jointed together. These animals have been 

 formed into a separate sub-kingdom called articulata orannulesa, 

 from this structure. The limbs, as we may see in the 

 cockchafer or the crab, are also formed of small hard cylinders 

 jointed together. The name insect itself comes from a Latin 

 word which implies formed of separate parts 



Insects undergo metamorphoses, that is, they do not emerge 

 from the egg in the form which they will assume later. They 

 also change their skin at different periods, which is called moult- 

 ing. Insects generally undergo two metamorphoses ; they con- 

 sequently pass through three stages ; that which lasts from the 



