72 DESCRIPTION of the 



They begin to rife out of the river ^5 or 40 minutes 

 after the fun fets and continue rifing about fifteen 

 minutes. 



We have no information concerning the larva: of 

 thofe infe»5ts. 



The cryfahs, in which form they rife to the furface 

 of the water, is not diftinguifhable from the perfe£t in- 

 fed: in fhape or colour. 



The cryfalis depofits a thin white pellicle or fkin on 

 the furface of the water and rifes a perfedl infedl. It 

 continues on the wing about an hour and perifhes. 



Some of them, not one in a hundred, rife from the 

 water in the form of a cryfalis. They fly immediately 

 to the fliore and in lefs than a minute they creep through 

 the white pellicle that covered the trunk, abdomen and 

 appendices, and rejoin their companions on the wing. 



In their flight they feldom rife more than fix or eight 

 feet above the water, but they ufually flcim or play near 

 the furface. 



The female drops two clufliers of eggs upon the water 

 and periflres immediately. 



The eggs are yellow. Each clufl;er is nearly one 

 quarter of an inch in length and the thlcknefs of a com- 

 mon pin, refembling the roe of a fifh and containing 

 about 100 eggs. They fink in the water. 



As thofe infedls are not feen to couple on the wing 

 it is prefumed that the male fecundates the eggs when 

 they drop on the water. 



Thefe flies are fo numerous that they appear fome 

 evenings like thick driven fnow in a cloud that is hardly 

 tranfparent. 



Thefe infedts, who differ in many particulars from 

 the ephemera, are not eafily reduced to any genus de- 

 fcribed by Linnaeus, Geoffroy or tscheffer. They muft 



be 



