£ PHEMERIDA . 87 



Family Ephemekid^e (Eph-e-mer'i-dae). 

 The May -flies. 

 In river or lake towns, during the warm evenings of late 

 spring or early summer, the electric lights or street lamps are 

 often darkened by myriads of insects that dash against them, 

 and the pavements are made slippery by their dead bodies 

 which have been trampled under foot. They are not the ordi- 

 nary night-flying moths: if an individual of the thousands 

 that cling to the posts and buildings in the vicinity of the 

 light be examined, it will prove to be a delicate creature with 

 oainty, trembling wings and two or three long, 

 white, thread-like organs on the end of its body ; 

 the body itself is so transparent that the blood 

 within can be seen pulsating. The front 

 wings are large and finely netted, and the 

 hind wings are small or absent (Figs. 94, 95). Fl 2* t wo"^inJed 

 So fragile are these pale beings that they seem ay ~ y ' 



like phantoms rather than real insects. No wonder that 

 poets have sung of them as the creatures that live only a 

 day. It is true that their winged existence lasts often 

 only a day or even a few hours ; but they have another 

 life, of which the poet knows nothing. Down on the 

 bottom of a stream, feeding on mud, water-plants, or other 

 small insects, lives a little nymph with delicate, fringed 

 gills along its sides and two or three long, many-jointed, 

 and often feathery appendages on the end of the body (Fig. 

 96). It has strong legs and can both walk and 

 swim. After about the ninth molt — there may be 

 twenty molts in all — there appear on its thorax 

 four little sacs which are the beginnings of wings ; 

 with each molt these grow larger, until finally the 

 last skin of the water-nymph is shed, and gills and 

 mouth-parts are all left behind, and the insect 

 comes forth, a winged May-fly. But there is still 



FiG.96.— Nymph ° . 



of May-fly. another change to be undergone. I he insect 

 has not yet reached the adult state. After flying a 



