THE NERVE-WINGED INSECTS 95 



of its wings, as is highly necessary if it is not to be drowned. Most 

 insects require several minutes or even hours for the wings to ex- 

 pand and harden, but Professor Comstock observed a caddis-fly 

 which took flight immediately upon emergence from the water. 

 The adults are usually grayish, brownish, or dusky in color, marked 

 with black or white, and are rarely observed except as they fly 

 into lights. 



Pseudoneuroptera, with incomplete metamorphosis. All of the 

 three orders just considered have a complete metamorphosis and are 

 more or less closely related. The next three orders are all aquatic 

 and have an incomplete metamorphosis, for which reason they are 

 often grouped together as false Neuroptera (Pseudoneuroptera). 



The May-flies (Ephemerida) l are well 

 named, for they are the most ephemeral 

 of insects. The wings are exceedingly 

 delicate and the fore-wings are much the 

 larger, the hind-wings sometimes being 

 entirely wanting. The mouth-parts of 

 the adults are exceedingly rudimentary, 

 and they probably take no food. The 

 antennae are short, but at the end of FlG - I22 - Net of a net-building 



' caddis-worm 



the long, soft abdomen are two or three 



. . , , . .... , (After Comstock) 



long, many-jointed, threadlike append- 

 ages, the cerci, which are quite characteristic of the May-flies. On 

 warm nights of late spring and early summer the lights of towns 

 near rivers and lakes are often darkened by myriads of May-flies. 

 They are light brown or dusky colored, with wings expanding from 

 one to one and one half inches, and with cerci fully as long. The 

 nymphs live at the bottom of ponds, streams, and lakes, feeding on 

 small insects and vegetable matter in the ooze. Along each side of 

 the nymph's abdomen is a row of delicate, platelike, fringed tracheal 

 gills, through which it breathes, and at the tip of the abdomen are 

 three feathery appendages. The legs are strong and enable it both 

 to walk and to swim. The nymphs molt very frequently, there being 

 in some species as many as twenty molts. After about the ninth 

 molt the wing pads commence to appear on the back, and become 



1 From ephemeras (lasting but a day). 



