104 INSECTS DIAGRAM 6. 



ABTICULATED ANIMALS, 



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 Invertebrata, that is, animals without vertebrse. 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 or Annulosa, 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 moulting. 

 Insects generally undergo two metamorphoses ; they consequently 

 pass through three stages; that which lasts from the time that 

 they emerge from the egg to their first metamorphosis is the larva 



