208 



NATURAL HISTORY. [cH. XIV. 



nences which, fringe the edges of the leaf. This 

 species of larva rarely swims about, but remains 

 concealed in little holes which they have pierced in 

 the banks of the river. These holes are ordinarily 

 directed horizontally, and their apertures are oval 

 (fig. 1). At first sight these innumerable holes ap- 

 pear to be placed confusedly and without any sym- 

 metry ; nevertheless it may be observed, on a nearer 

 inspection, that some are much larger than others, 

 and that the large ones are very oval and stand 

 isolated, while the small ones are more circular, and 

 are placed in pairs on the same horizontal line; after 

 a slight examination, the reason of the proximity of 

 the smaller circular holes is apparent, for the two 

 apertures are found to belong to one habitation, and 

 the dwelling of our ephemerae observed to be not so 

 simple as that of the earth-worm. It is, in fact, a 

 bent tube (fig. 2); and the advantages of such a 

 construction are evident. The insect, after enter- 



FlG. 1. 



Fig. 2. 



ing, can go out w^ithout crawling backwards, or with- 

 out making that awkward turn which it would be 

 forced to do if in a straight hole ; in fact, our ephem- 

 era has a door for going in and another for coming 

 out. The large oval holes are caused by the parti- 



