VIII MAY-FLIES 293 



sides of the segment [in advanced larvae] are the 

 sheaths of the wings. Air-tubes ramify upon the 

 sheaths, and shortly before a moult, the wings may 

 be seen within them, folded up in a wonderful 

 and beautiful manner. The third thoracic segment 

 bears the second pair of wings, which are much 

 smaller than the first, and also a pair of five-jointed 

 legs. The first segment of the abdomen is smooth 

 and provided with no appendages, the next six 

 segments are furnished with gills, which are in 

 incessant movement. In the Lobster, Crab, and 

 Sepia,^ which in many respects approach the structure 

 of Insects, we find the gills formed and arranged 

 in nearly the same manner, though with this difference 

 that in Crabs and Lobsters the gills are enclosed by 

 a hard carapace, while both in them and in the Sepia 

 they are more concealed than in the Palingenia-larva. 

 The eighth and ninth segments of the abdomen are 

 simple and smooth. The tenth or last abdominal 

 segment is furnished with three hairy filaments ; 

 besides these, there arc two small curved appendages 

 (claspers) which are not so conspicuous in the female.- 

 To these are added in the male yet another pair of 

 small appendages beneath the others. 



" The colour of the larvas, when very small, is pale 

 blue, verging upon green. This colour belongs rather 

 to the viscera than to the skin. The eyes are dark 



^ The correspondence between the gills or any other organs 

 of Sepia, and those of an Insect, is very far from close. 



- On the under side of the last abdominal segment of female 

 Ephemeras, a pair of minute appendages can be made out, 

 which are the parts intended by Swammerdam. 



