262 NATURAL HISTORY. 
Fig. 207. 
The Aishna, 
a aa 
lice. In the first three of these families, the insect in its 
larva and pupa states inhabits the water, respiring like a 
fish, having peculiar organs for this purpose at the sides 
of the abdomen or at its end, while in the form of its 
body it is quite like the insect in its perfect state. 
450. Of the Dragon-flies, the most conspicuous and 
best-known family, there are about two hundred ascer- 
tained species. These are the Swallows of the Insect 
