THE INSECTS. 329 



clusters, which rapidly burst, and the eggs sink, and lie 

 broadcast on the bottom of the river. 



The less perishable species extrude their eggs gradually, 

 part at a time, and deposit them in one or other of the fol- 

 lowing manners : Either the mother alights on the water 

 at intervals to wash off the eggs that have issued from the 

 mouths of the oviducts during her flight, or, as Mr. Eaton 

 has himself observed, she creeps down the stem of a plant 

 into the water, enclosed in a film of air, and deposits her 

 eggs (the wings being collapsed so as to cover up the abdo- 

 men) under stones, &c., and on completing her labour, floats 

 up to the surface and flies away. But at times her setae 

 get wet ; she is unable to extricate herself, and is drowned. 



A letter in the Field of April 10, 1886, from Mr. W. F. 

 Beart, of Godmanchester, corroborates these observations. 

 He was returning from fishing in a stream in Bedfordshire 

 in the early part of May, 1885, when he noticed near a 

 wooden bridge a number of spinners, some on the water, 

 some in the air. His attention was attracted to an insect 

 sitting on a post of the bridge, quite close to the water 

 an olive dun. He saw it walk down the post head fore- 

 most into the water, the pressure of which appeared to 

 double the wings flat on the back, and so disappeared. In 

 about a minute it walked up the post again, no longer an 

 olive dun, but a spinner. He was so much interested 

 that he remained for an hour, and saw a number of olive 

 duns do the same thing, some rising into the air, others 

 floating down the stream on the surface of the water. 



Mr. Eaton says : " The duration of the egg state varies 

 with the temperature to which they are exposed " and 

 makes some interesting remarks as to the power of living 

 of the Nymphce in relation to the temperature of the water. 

 He says : " Besides the influence of flood and drought, or 

 constancy of supply, the climate of the water is largely 

 concerned in determining the fitness or unsuitability of a 

 particular site for particular kinds of the Ephemeridce. A 

 knowledge of the water climate needed by a species renders 

 intelligible the limitation of its geographical and local dis- 

 tribution. The temperature of the ordinary land-springs 



