12 



The growth of insects always takes place during the 

 larval portion of the life-cycle. Caterpillars, for Instance, 

 moult, or shed their skin. Pour or five times during their 

 growth, from hatching to pupation. Adult insects do not 

 grow in size. Once tin* wings have been developed, the 

 insect is full-grown. Small flies do not grow into big flies, 

 small moths do nut grow into Larse ones, nor small beetles 

 i nto Large beet Les. 



It should be remembered that butterflies and moths, 

 beetles, Hies, beesand wasps all develop Prom a Larval stage 

 which is very different in appearance from the adult form, 

 and that the change in appearance is brought about in the 

 period of pupation. On the other hand, such insects as 

 grasshoppers, cockroaches and cotton staiuers, which have 

 an incomplete metamorphosis, are in the immature stages 

 somewhat like the adult in general form, but without wings 

 or with developing wings. In the case of any insect, how- 

 ever, the winged individual is the adult. 



Senses. 



Insects have well developed senses of taste, smell, 

 hearing and sight. They have also well organized digestive, 

 nervous, circulatory, and respiratory systems. 



It is next to impossible to determine exactly the 

 functions of certain sense organs in insects. The organs for 

 seeing, hearing and for producing sound can be recognized 

 by their structures, and by experiment, but there are others, 

 the function of which it is not so easy to determine. 



The sense of taste is probably located in the small 

 appendages of the mouth parts, the senses of smell and hear- 

 ing are, in some insects at least, in the antennae, which are 

 often the most conspicuous appendages of the head. Special 

 organs of hearing are sometimes (in certain Orthoptera) to 

 be found on the abdomen and legs. The sense of sight 

 depends on the eyes, which are of two kinds, simple and 

 compound. The compound eyes are often made up of many 

 facets and are located at the sides of the head, while the 

 simple eyes, or ocelli, are situated between them, either on 

 the top or the front of the head. 



The simple eyes of insects are not always present, but 

 when they occur, they are two or three in number. The 

 compound eye is perhaps the most complex and delicate 

 structure in the insect world. 



