270 



ZOOLOGY 



stages passed in fresh water. The stone flies have 

 two tails, and the wings fold over the body as in the 

 cockroaches. The similar segments of the thorax in 

 the young closely resemble those of very ancient fossil 

 insects. The antennae are long and slender. The May 

 flies, noted for the brief period of their adult life, usually 

 have three tails, while the antennae are short and incon- 

 spicuous. 



Order Odonata 



Dragon flies The dragon flies ; usually large insects, passing their 

 early stages in the water, the ugly young being absurdly 

 called nymphs. They are carnivorous in all stages. 

 The larva is active, and has no resting stage before 

 transforming into an adult. The adult insect has biting 

 mouth parts, very small, threadlike antennae, and very 

 well developed wings. The species differ greatly in 

 size, one having wings only about 9 mm. long, while in 

 another the hind wing of the female reaches 94 mm. 



From Bulletin 67, U. 5. National Museum 

 FIG. 83. A dragon fly (Plathemis) . 



