154 THE ENTOMOLOGIST. 



A GUIDE TO THE STUDY OF BRITISH WATERBUGS 

 (AQUATIC HEMIPTERA OR RHYNCHOTA). 



By G. W. Kirkaldy. 



(Continued from p. 83.) 



Plea, Leach.* 



Resembles an animated grain of sand. There is a single 

 British sjoecies : — 



1. P. LEACHi, McGregor & Kirkaldy (= minutissima, Fabr., 

 nee Linn6). Generally distributed. It is probably N. atomaria, 

 Pallas. It has a funny paddling gait in the water, more like 

 certain beetles than any of its allies. It probably oviposits in a 

 similar manner to Notonecta. 



This closes the account of the true waterbugs belonging to 

 the Pagiopodous division. We now have to consider an aquatic 

 family of the Trochalopoda, viz., the Nepidse, containing two 

 British forms, Nepa cinerea and Ranatra linearis. 



Fam. Nepid^. 



The Nepidae are apparently descended from a protoreduvioid 

 stock, and have, like the aquatic Pagiopoda, become modified for 

 existence in their newer habitat. Their most conspicuous dif- 

 ferential character is the filamentary caudal tube, which is used 

 for respiratory purposes, and is simply two elongate, modified 

 spiracles, and which varies in length according to the species. 

 Fieber, in his anxiety to ally the Nepidte to the Belostomatidse 

 (a family of giant, extra-British waterbugs), termed these fila- 

 ments " aidothecal appendices," although they have been known 

 certainly to be respiratory, not sexual, for one hundred and 

 seventy-eight years ; while taking in a fresh supply of air the 

 end of the tube is simply thrust out of the water. In the 

 nymphs the tube is shorter and stouter. 



The head is porrect ; the rostrum short, stout, and curved, 

 composed of three (apparent) segments ; the body flat in Nepa, 

 subcylindric in Ranatra ; the antennse are composed apparently 

 of three short segments, the second of which is produced later- 

 ally. In the water the legs are moved alternately, in contrast to 

 the aquatic Pagiopoda, in which they are moved synchronously ; 

 the anterior pair are strongly raptorial, the other pair slender, 

 not ciliate ; the tarsi are not segmentate, and terminate in two 

 claws. Their gait is leisurely, a sort of paddling rather than 

 swimming. They remain motionless for hours concealed, or 

 partly concealed, in the mud of the ponds or canals in which 

 they live, or clinging to the stems of water-plants, lying in wait 

 for such prey as they can overpower, not sparing their own kin, 



■•'• From Greek pleo, I swim. 



