X 



POND-SKATERS 



351 



Fig. 105 



Very young larva 

 of Gerris, natural size, and 

 magnified. 



dimples cast shadows on the bottom, each surrounded 

 by a bright ring, due to refraction of the raj-s wh-ich 

 pass through the curved surface. 

 But the central shadow, cast by 

 the body of the Insect, has no 

 bright ring, and when the animal 

 moves, no bright ripples appear 

 about the central shadow, such 

 as accompany the movements 

 of the legs. The body does 

 not actually touch the water.^ 

 Meinert observes that Gerris has 

 three modes of moving about on 

 water, (i) drifting by wind or 

 cuo'ent, (2) skating, and (3) 

 leaping. A small species, G. lacustris, can leap a few 

 inches on the surface of water, but a greater distance 

 on solid ground. Gerris dives occasionally but not 

 often, and never when avoiding pursuit. An allied 

 species, X'^elia currens, though less nimble than Gerris, 

 swims under water more readily. At times it can be 

 seen to run, back downwards, on the surface-film, 

 completely immersed in the water ; its abdomen at 

 such times glistens with the air-bubble which over- 

 spreads it. 



All these surface-Rhynchota live by sucking the 

 juices of dead or dying Insects blown or in some 

 other accidental way brought to the surface of the 

 water. The beak is driven into the body, and kept 

 there for a considerable time until the av^ailable juices 

 have been extracted. 



^ Meinert, Saef fry^- af Entomol. Meddeleher, 1887, 



