, MAY-FLIES. 63 



to devour the eggs of other insects and fish, thus 

 maintaining the grand cycle of extinction and re- 

 production which obtains over the whole wide do- 

 main of nature. The larvae, being essentially aquatic 

 animals, must be furnished with organs, analogous to 

 the gills of fish, for the purpose of respiring the sur- 

 rounding fluid. They are a series of fin-like fringed 

 appendages, extending down each side of the abdo- 

 men, and by and in these, which are continually in 

 motion, the air is decomposed or separated from the 

 water, and conveyed through spiracles to the tracheae. 

 Besides the lateral appendages, the larvae have three 

 pairs of limbs on the forepart of the body, which 

 enable them to crawl and swim about at pleasure. 

 The pupae differ little from the larvae except in their 

 larger size, and that in the more advanced state the 

 future wings can be perceived carefully encased over 

 the thorax. In no instance, as has been erroneously 

 asserted by some writers on fishing, do any of the 

 Ephemeridae form a case or caddis to dwell in, as their 

 neighbours the Phryganidae or stone-flies do ; but, 

 in both the larvae and pupse states, the Ephemeridae 

 form holes at the bottom and the sides of the stream, 

 wherein they can avoid the too officious attentions of 

 their fishy friends. The length of time they remain 

 in these states is unknown, probably it extends from 

 one to two, or even three years. At the period of 

 their penultimate transformation, the pupa, rising 



