How they are constructed 



It will be noticed that the insect has its 'heart' along its back, and 

 its main nerve-cord along its front, or ventral side; the reverse of our 

 own structure. 



Immature Stages of Insects 



These have been mentioned briefly in the preceding chapter, and are 

 discussed again in Chapter III, under the topic of reproduction in 

 insects, so there is no need to say any more about them here. 



The Size of Insects 



According to Borror and Delong (1954), insects range in length from 

 one-hundredth of an inch to more than eight inches, and in wing-span 

 from one-fiftieth of an inch to nearly a foot. The biggest wing-span 

 among living insects is to be found in giant moths, though some extinct 

 dragonflies were even bigger. The longest and thinnest insects are cer- 

 tain stick-insects, while the bulkiest are certain beetles and water-bugs. 



The beetles are remarkable in that the Order Coleoptera includes 

 nearly half of all the known species of insects, and some of the very 

 smallest as well as some of the bulkiest. 



"^ 



Fig. 18. An attractive insect of the Order Neuroptera, family Ascalaphidae 



33 



