148 THE ENTOMOLOGIST. 



A GUIDE TO THE STUDY OF BRITISH WATERBUGS 

 (AQUATIC RHYNCHOTA). 



By G. \V. Kirkaldy, F.E.S. 



(Continued from vol. xxxii. p. 300.) 



The true "waterbugs" — i.e. those which pass the greater 

 portion of their existence actually beneath the surface of water — 

 whether it be running stream, stagnant pond, or brine pool—and 

 which are considerably modified in their structure in accordance 

 with their environment — have been usually placed in a single 

 division by modern authors, partly for convenience, and partly 

 from a mistaken idea of the taxonomic importance of one or two 

 characters, e.g. the great alteration in the magnitude and situa- 

 tion of the antennae, which in the majority of the forms are con- 

 cealed when at rest in grooves on the under side of the head, 

 whence the group is usually termed Cryptocerata (or Krypto- 

 kerata).* This modification is, however, evidently not a test of 

 relationship, but connected with the nature of their habitat. In 

 the same way that coleopterists perceived at length that the 

 Dytiscidge, Gyrinidse, Hydrophilidae, &c., were really not closely 

 allied, despite their common habitat and their superficial re- 

 semblance, so have many rhynchotists now realised that there 

 are two heterophyletic divisions — probably very distantly related 

 — of aquatic bugs. 



The first of these — the Naucoroidea— embraces the British 

 families Naucoridae, Corixidse, and Notonectidse, and the exotic 

 Mononychidae (which should perhaps be included in the Nau- 

 coridse) and Belostomatidae. The second — the Nepoidea— con- 

 tains a single family, the Nepidae, with two British genera, viz. 

 Nepa, Linn., and Ranatra, Fabr. The Gerridae, which have 

 previously been discussed, are related more nearly to the 

 Nepoidea than to the Naucoroidea, but have in any case arisen 

 quite separately, probably from a proto-Eeduvioid stock, from 

 which indeed the Nepoidea also probably originated. 



The first step towards an aquatic life to which Notonecta has 

 become so admirably adapted would be represented by a bug not 

 unlike Acanthia, Fabr. Latr. [Salda, Saund.], a genus of which 

 we have eighteen species in our islands. These are most diverse 

 in their habits, most of them frequenting the margins of 

 streams, ponds, salt marshes, often under stones : one species is 

 to be found in Sphagnum ; while another occurs far away from 

 moisture on sandy commons or moors, under heather or in sand- 

 pits. Two species at least move about from plant to plant 



* Greek xpt^Trroj (Icruptos), hidden ; «spa; (keras), a horn. 



