CHAPTER III. 

 Natural History of Insects. 



STRUCTURE AND GROWTH. 



As has been stated already, insects are animals which, 

 in the adult condition, have never more than six legs, and 

 generally, two pairs of wings (which may be wanting but 

 are never more in number), and a body made up of three 



Fig. 9. Insect with incomplete metamorphosis. A cockroach. 



(a^ (b) (c) (d) immature stages ; f e) adult ; (/) ahdt with eg/ case; 



(h) adult with wings spread; (g) egg case. All natural size except 



(g) which is enlarged. (From U.S. Dept. Agric.) 



distinct parts head, thorax and abdomen. The legs are 

 attached to the thorax, one pair to each segment ; the fore 

 and hind wings ire attached to the second and third seg- 

 ments, respectively. The head and abdomen have no organs 

 of locomotion. To the head are attached the mouth parts, 

 and the antennae, which are sensory organs. The abdomen 

 also sometimes has sensory organs. Fig. 9 shows the cock- 

 roach and the attachments of wings and legs. 



In the case of most insects, the adult deposits eggs from 

 which the young are hatched. There are instances, however, 

 among these animals, in which the young are already hatched 

 from the egg at the time when they are born. That is to say, 

 they are active and free-moving, having accomplished one 

 stage of their existence within the body of the parent. 



