194 THE EPHEMERINA. 



filaments, and even those species which, when mature, 

 have only two of these appendages, possess three in 

 the larva state. The branchial plates, those delicate 

 leaf-like organs with which the sides of the abdomen 

 are furnished, are often of the most beautiful con- 

 struction. They form double leaves springing from a 

 common base on each side of the six first segments 

 of the abdomen ; into each of these leaves a strong 

 trachea passes, and becomes divided in their substance 

 into numerous delicate branches. In some cases the 

 gill-plates are fringed all round with delicate hairs, in 

 others their margins are naked, and in others one of 

 the leaves in each pair is converted into a tuft of 

 delicate filaments. 



On arriving at maturity the pupa mounts to the 

 surface of the water, where it often floats whilst its 

 integuments burst, and give issue to the perfect 

 insect, which, however, although capable of flight, is 

 still enclosed in an exceedingly delicate membrane. 

 Flying heavily they reach the shore, where they 

 attach themselves to the stems of plants, posts, and 

 other objects, frequently even settling upon the 

 clothes of the passers by, and in these situations most 

 of them quickly get rid of their last envelope, which 

 they leave adhering by its claws to the object which 

 has served them as a support. In some cases, how- 

 ever, as Mr. Westwood observes, the last garment of 

 the immature insect is not cast off until more than 

 twenty-four hours after its emergence from the 

 watery home of its youthful days. After escaping 

 from this pellicle the insect always appears of a 

 brighter colour, with its wings more transparent and 

 glistening, and what is still more remarkable, the tails 

 often grow to double their previous length. 



