Nymph x 6 



MAYFLIES, DUNS AND SPINNERS 233 



nymph of Baetis, one of the genera with swimming 

 nymphs. 



According to Pictet the nymphs belonging to this 



division have been the worst 

 Crawling nymphs. treated by nature. Not having 



powerful mandibles and muscu- 

 lar forelegs like the digging nymphs, having neither 

 the strength of the flat nymphs, nor the fin-like tail 

 of the swimming nymphs, they Fig. 41. blue-winged Olu-e 

 are slow in their movements, 

 unable to dig, and thus escape 

 from their numerous enemies, 

 and could not well secure their 

 prey if they did not make up by 

 cunning for what is wanting in 

 strength and agility. They live 

 in parts of the stream where the 

 flow is not very rapid, and are 

 prone to shelter in gravelly 

 places on the bed of the river. 

 They envelop themselves with 

 a thin coating of mud or other 

 detritus, and are often almost 

 invisible under such conditions. 

 At the same time the small 

 larvae and other creatures on 

 which they feed cannot dis- 

 tinguish these nymphs lying in ambush, and fall an 

 easy prey to them. Fig. 41 shows a nymph of the 

 blue-winged olive, which is the type of this division. 



