200 THE ENTOMOLOGIST. 



A GUIDE TO THE STUDY OF BRITISH WATERBUGS 

 (AQUATIC RHYNCHOTA). 



By G. W. Kirkaldy. 



(Continued from p. 154.) 



Brulle, however, noted* that some individuals of a species 

 of Gerris plunged rapidly beneath the surface upon attempted 

 capture. 



The foregoing and ensuing experiments and notices were 

 made, as far as possible, on individuals in their natural habitat 

 as well as in confinement, but it is of course exceedingly difficult 

 to make minute observations upon such insects in the open. 



The velvet-like pubescence, with which these insects are 

 clothed, has been previously referred to as permitting the 

 insect to respire without inconvenience by forming an air- 

 bubble around it when beneath the surface, and also as pre- 

 venting the entrance of water, either when submerged or by 

 chance spray, into the trachaeal system. 



Meinert instances another scarcely less important use, viz. : 

 that this air-investment enables the insects, after diving be- 

 neath the surface, to commence respiration of the upper air at 

 once, allowing them to come up perfectly dry. In fact, this 

 air bubble serves much the same purpose as the space between 

 the elytra and the dorsal surface of the abdomen in Dytiscus, 

 Ilyocoris, Corixa, &c, and the lateral grooves covered with two 

 fringes of strong hairs on the venter in Notonecta. But it is 

 necessary to the effectual working of the pubescence that it 

 should be perfectly clean and free from dirt. I have previously 

 remarked on the incessant care with which the Gerridae cleanse 

 themselves ; and, taking into consideration the longer legs in 

 Gerris, the process is very similar to that already described in 

 Hydroessa. 



In nature, although Gerris is perhaps as common on small 

 ditches and pools as on larger sheets of water, it by no means 

 keeps to the shelter of the shore of the latter, making fairly long 

 excursions out, and therefore does not thrive well, as a rule, in 

 captivity. 



When imprisoned in even a fair-sized bowl, they knock their 

 heads and fore legs continually against the sides of the bowl, 

 become enfeebled, subsequently water-logged, sinking at last to 

 the bottom and there perishing. 



Gerris is not at all of a timorous nature ; with care, one can 

 approach very close to them and observe them superficially with- 

 out difficulty, and can even with a well-timed, rapid movement 

 catch them with one's fingers. They are not, as a rule, disturbed 



* ' Histoire uaturelle, Insectes,' vol, ix, 



