418 



THE INSECT WORLD. 



vulgata, Fig. 389), is of a brown colour, banded with yellow, and 

 the wings smoky, with brown spots. These insects are remarkable 

 for their elegant flight; they are continu- 

 ally rising and falling. When they move 

 their wings, they rise ; but if their wings, 

 though spread out, remain motionless, as 

 also the silky hairs which form their tail, 

 they fall again. They may be seen in 

 myriads in places where there is much 

 water. 



We have said that the Ephemera live 

 only for a few hours. This is the general 

 rule ; but their existence can be prolonged 

 for ten or fifteen days by preventing their 

 copulation. If, however, the duration of 

 the life of these insects is so short when 

 they have reached the perfect state, which 

 is when the conformation of the mouth pre- 

 vents them from taking any nourishment, 

 their larva state is of very long continu- 

 ance. Swammerdam says, in his curious 

 memoir, entitled "Vita Ephemeri," it is 

 not less than three years. 



The females lay their eggs in one single mass, and let them 

 fall into the water, in the form of a packet. The larvae which 

 come out of them are very active, and swim with great ease ; but 

 generally conceal themselves under the pebbles at the bottom. 

 The sides of their abdomen are provided with gills, very much 

 fringed, which serve them, not only for breathing the air under 

 the water in the same way that fish do, but also for swimming. 

 The larvae have, at the extremity of their body, two or three 

 hairs, like the perfect insect. They hollow out galleries in the 

 beds of rivers and ponds, and live on small insects. The pupa 

 (Fig. 391) differs only from the larva (Fig. 390) in having 

 the rudiments of wings. When about to undergo their meta- 

 morphosis, they come out of the water and cling to plants, &c. 

 The skin cracks on the back when it is dry, and there comes 

 out a heavy insect, which flies feebly, and has opaque wings. 



Fig. 389. Ephemera vulgata 

 imago. 



