366 NATURAL HISTORY OF AQUATIC INSECTS CH. 



terrestrial species are able to support themselves on 

 smooth vertical surfaces by help of this adhesive 

 organ, which opens by a slit, and gives passage to a 

 fleshy sucker. 



The aquatic Spring-tail, says De Geer, perished in 

 two or three hours when removed from the water, 

 and its body shrunk as if by evaporation. He was 

 inclined in 1740 to suppose that the tubercle mentioned 



FIG. 112. Isotomapalustris (Aquatica cinerea of De Geer). a, the forked appendage 

 or spring ; b, the adhesive organ, or ventral sucker, seen also between the hind 

 legs in the upper figure ; c, claws at extremity of leg. x 60. 



above sucked up water for the supply of the body 

 when the Spring-tail floated on its native pools. 

 Having placed some of these Insects in a vessel 

 completely full of water, he observed that they crept 

 to the bottom, and lived for several days. They did 

 not apparently possess any power of swimming. 



The smaller and less common Isotoma palustris is 

 also described, but De Geer gives little information 

 as to its habits. 



It is easy to find aquatic Podurae in ditches and 



