THE EPHEMEKIDyE. 353 



This is curious enough, for it is not often that the de.'jraded 

 condition so commonly observable in the wings of female insects 

 is to be found in the males, and it is very interesting that such 

 closely-allied insects should have such remarkable differences of 

 structure. 



The EphemeridcB exist in enormous numbers, and last for the 

 shortest time imaginable in their perfect state. They are the 

 lightest, the most fragile, and the most delicate creatures in the 

 world. They float away in the air from off the water, in which 

 they have lived during the early stages of their existence, flutter 

 in the sunshine, dance about with every breeze, and they grow 

 faint as the sun gets low, and sink and die with the night. 

 They are truly ephemeral beings. They can be easily dis- 

 tinguished. They have very short antenna, ending with an 

 extremely delicate silk-like thread ; their wings are very fine, the 

 front ones are the largest, the hind ones being very small ; the 

 body is terminated by two or three long-jointed bristles ; the 

 structures of the mouth are soft, and cannot receive food, and 

 indeed the perfect insects, living as they do only a few hours, 

 never think of wasting their lives in eating and drinking. They 

 all exist for love, and they spend their short day in a constant 

 and active courtship. The eggs are laid in little packets upon 

 the water. As soon as the larvae escape from the &^^ they take 

 to the water, and grow more or less rapidly, according to the 

 species. These larvse are essentially aquatic insects, and are 

 organised so that they can respire in water, for there are gills, or 

 delicate folds of skin, which are traversed by numerous tracheae 

 fixed on to their bodies. The larvae of all the species of the 

 genus Ephejnera are very similar, and they are believed to live 

 two or three years before they begin their transformations. They 

 reside beneath stones or in burrows at the bottom of running 

 streams, and they undergo an incomplete metamorphosis. They 

 have very strong jaws covered with spines, and mandibles with 

 sharp points to them. They begin to be nymphs when the rudi- 

 ments of wings appear. When the nymph is full grown^ it crawls 

 out of the water on to plants or stones, and its skin cracks 

 down the back and the adult emerges from it into the air. But 

 this perfect insect is covered over and entirely enclosed in a 



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