MOTIONS OF INSECTS. 295 



move in midwater, either by the same motion of the 

 legs as they use in Avalking, or by strokes, as in swim- 

 ming ; others for this purpose employ certain laminjB, 

 which terminate their tails, as oars ; others again swim 

 like fish, with an equable motion ; some move by the 

 force of the water which they spirt from their anus; 

 others again swim about in cases, or crawl over the 

 submerged bottom ; and others Avalk even on the sur- 

 face of the water. I shall not now enlarge on all these 

 kinds of water-motion, since many will come under 

 consideration hereafter. 



There are two descriptions of larvae of ITi/drophili^ 

 one furnished with swimmers or anal appendages, by 

 means of which they are enabled to swim ; the other 

 have them not, and hence are not able to rise from the 

 bottom^. The larvae of D?/tisci, by means of these nata- 

 tory organs, Avill swim, though slowly, and every now 

 and then rise to the surface for the sake of respiration. 

 Those o^ Ejihemerce, when they swim, apply their legs 

 to the body, and swim with the swiftness and motions 

 of fish''. Those of the true may-fly (Seniblis Intaria, 

 F.), on the contrary, use their legs in swimming, and 

 at the same time, by alternate inflexions, give to their 

 bodies the undulations of serpents '^. But the larvae of 

 certain dragon-flies (Aes/ina and Libellula^ F.) will af- 

 ford you the most amusement by their motions. These 

 larvEB commonly swim very little, being generally found 

 w alking at the bottom on aquatic plants ; when neces- 

 sary, however, they can swim very well, though in a 

 singular manner. If you see one swimming, you Avill 

 find that the body is pushed forward by strokes, be- 



^Miger, ^nn.(f«iHHS. xiv.441. " Dc Geer, ii. 621, Mbid.'S:— 



