ii2 ROD AND RIVER 



creepers so transported, and that it is necessary 

 for their well-being that the mud in which they 

 are found should be taken with them. Where 

 this had not been done the experiment had failed, 

 but where it had been attended to it had been 

 successful. The mud so taken had, by degrees, 

 been incorporated with that taken from the river 

 into which it was desired to introduce the creepers ; 

 and so, by gradually and increasingly adulterating 

 the former with the latter, the creepers had become 

 accustomed to it and fitted to take up their new 

 quarters. 



Kirby and Spence state that the lives of the 

 Ephemera vary in the creeper state from one to 

 three years, the several varieties differing con- 

 siderably in this respect. De Geer states that he 

 experimented with the larvae of mayflies, in order 

 to test the duration of the period in which they 

 remained in that stage, and with the following 

 results : Some, which he kept in Brittany, re- 

 mained in the larval condition for between one 

 and two years ; while others in North Holland 

 required three years to hatch out. 



In his work on the ' Classification of Insects/ 

 Professor Westwood states that De Geer suc- 

 ceeded in keeping some Ephemera alive for eight 

 days, and that a Mr. Stephens contrived to do 

 so for over three weeks ; adding that, if they had 

 been left to live in a natural state, they would 



