222 



NORTH AMERICAN INSECTS. 



1. Libellula, with a flat, short body (Fig. 57). 



2. sEshna, with a round, cylindrical body (Fig. 58). 



3. Affrion, with a small body, short, broad head, in which the eyes 



are placed at a distance from each other (Fig. 59). 



The wings of the first two genera are always horizontally 

 expanded ; but the wings of the last genus, when at rest, 



are directed backward, 

 touching each other. They 

 have four jaws, which are 

 covered with a helmet-like 

 membrane, giving them an 

 ugly, ferocious appearance, 

 but which is really nothing 

 more than the under-lip, 

 with which they are ena- 

 bled to seize their prey. 



The larvae, or grubs of 

 the dragon-fly, live in the water. Those of the genus Li- 

 bellula are short and thick ; those of JEshna are longer ; 

 and those of Agrion are very slender, and the smallest of 

 all. Their color is generally brownish green ; their head, 

 thorax, and hind body distinctly separated, and the latter 

 composed of ten ringlets. They swim quite well. Their 

 breathing is effected by the hind extremity of the body, 

 as any one may observe who will take them out of the 

 water and leave them so about a quarter of an hour, and 

 then put them into a flat vessel scarcely covered with 

 water. 



After spending ten or twelve months under the water, 

 these larvse transform themselves into the perfect-winged 

 insect, and henceforth live in the air. Their metamorpho- 

 sis may be almost daily observed from the month of April 

 until October, but occurs principally in the months of May 

 and June. But this transformation does not take place in 

 the water, but out of it; and, when ready for their meta- 



