106 FRESH WOODS. 



vulgata, the only ones I have been able to 

 observe in this division, are very difficult to 

 keep for a long time, and I have only been 

 able to preserve them for a few months." 



Concerning the manners and customs of 

 these EphemeridcB during their subaqueous 

 existence, it is very interesting to learn from 

 Pictet, in relation to the metamorphoses 

 of these insects, that there are great diffe- 

 rences between the species. Some, long and 

 cylindrical, armed with strong and trenchant 

 claws, can dig out galleries for themselves in 

 the earth. Others, large and fat, are incap- 

 able of digging, live always in the open water 

 attached to stones, and are easily caught. 

 Others, again, thin and delicate, are supplied 

 in their pliant tail with an instrument for 

 swimming, and these find retreats in mosses 

 and aquatic grasses. Besides these, there 

 are others still more feeble, and the latter, 

 being unprovided with the means of swim- 

 ming, lie in ambush, and seize their prey by 

 strategy. 



The larvae of the Ephemera and the Palin- 

 genia have very marked differences in the 

 form of their mandibles and respiratory 

 organs, but they have also many similarities ; 

 both are long, subcylindrical, with a small 

 pointed head. They seek standing waters, 



