338 



COLLEGE ZOOLOGY 



Fig. 259. — Order 

 Aptera. Campodca 

 stapkylinus. (From 

 Sedgwick's Zoology, 

 after Lubbock.) 



Fig. 260. — Order 

 Aptera. Lepisma 

 saccharina, the fish- 

 moth. (From Sedg- 

 wick's Zoology.) 



other interesting species 

 is the snow-flea, Achorutes 

 nivicola, which is some- 

 times a pest in maple 

 sugar camps, since large 

 numbers collect in the 

 sap. 



Order 2. Ephemerida. 

 — May-flies (Fig. 261). 

 — Insects possessing deli- 

 cate membranous wings, 

 with many cross veins ; 

 the fore-wings large, the 

 hind wings small or want- 

 ing; mouth-parts poorly 

 developed; metamorpho- 

 sis incomplete. 

 The young (nymph) may- fly (Fig. 261, A) lives in the water 



and breathes by means 



of tracheal gills. After 



from one to three 



years, depending upon 



the species, the nymph 



emerges from the 



water and becomes a 



winged adult (Fig. 



261, B). This adult 



is said to be in the 



subimago stage, since 



it moults after acquir- 

 ing wings. No other 



insect is known to do 



this. The paired con- 



Fig. 261. — Order Ephemerida. A, nymph of the May-fly. k, tracheal! 

 gills; I, principal trunk of tracheal system. B, adult May-fly. Af, anal | 

 filaments. (From Sedgwick's Zoologv.. 



