THE DRAGON FLIES AND THE MAY FLIES 27 



To this type belong the best fliers of the group. The insects 

 which illustrate the other type, while they can easily enough 

 be recognized as dragon flies, are of more slender build. These 

 are commonly called damsel flies. Their eyes are widely sep- 

 arated on opposite sides of the head. The anterior and pos- 

 terior wings are alike in size and shape, and when not in 

 use are folded against the abdomen. The flight is less sus- 

 tained and more erratic than that of species of the first type. 

 Definition of Odonata (Gr. odous (odont-), " tooth"). The 

 dragon flies constitute the order Odona'ta, a word meaning 

 "toothed," perhaps in allusion to the teeth on the labium 

 of the nymphs. The Odonata are distinguished by the bit- 

 ing mouth parts and the four equal or nearly equal net- 

 veined wings. Though the nymphs do not closely resemble 

 the adults, there is no conspicuous change from one molt 

 to the next, except at the last molt. Then the fully formed 

 wings of the adult are liberated from the wing pads of the 

 nymph. Although the nymphs resemble the adults less 

 than in the case of grasshoppers the Odonata likewise have 

 incomplete metamorphosis. 



The sun comes forth and many reptiles spawn ; 

 He sets and each ephemeral insect then 

 Is gathered into death without a dawn, 

 And the immortal stars awake again. 



Shelley 



May Flies. The May flies (Fig. 14), which stand in litera- 

 ture as the type of brief and purposeless existence, are deli- 

 cately constructed, pale insects, with usually four finely 

 veined wings and two or three long, white filaments project- 

 ing from the end of the abdomen. The eyes are compara- 

 tively large, but the mouth parts are so reduced that no 

 food can be taken during adult life, which in most species 

 lasts only a few hours. May flies appear in countless num- 

 bers in late spring or early summer, dance about in the air 



