212 MINUTE MARVELS OF NATURE 



species, its metamorphoses are completed, and 

 the animal leaves the water to become a wing-eel 

 May-fly. Fig. 140 shows the larva of a May-fly. 

 It is a mistake to suppose that May-flies only 



Fig. 140. Larva of May-fly, 

 x 4 diameters 



appear during- May, as various species arrive at 

 maturity at different periods during the summer 

 months. But the regularity of emergence of each 

 species is remarkable, and the phenomenon of the 

 sudden appearance of immense swarms without 

 any warning is a spectacle which familiarity never 

 stales. 



The rise, as it is called, of the flies usuallv takes 



