. 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 larve, 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 trachez. 
Besides the lateral appendages, the larve have three 
pairs of limbs on the forepart of the body, which 
-enable them to crawl and swim about at pleasure. 
The pupe differ little from the larvee 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 
Ephemeridee form a case or caddis to dwell in, as their 
neighbours the Phryganide or stone-flies do; but, 
in both the larvee and pupe states, the Ephemeride 
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 
