512 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



Group 10. 



Anterior tarsi of male never greatly incrassate, their claws more or less elongate, 

 their undersurface bearing distinct, but not large, palettes. Prosternal process 

 elongate, never broad, but little compressed and not carinate ; metasternal groove 

 rather long ; wings of metasternum rather large ; hind coxae moderately developed, 

 their front border not much arched ; swimming legs moderately slender. 



Twelve species from both Old and New Worlds. 



706. Dytiscus congener, Payk., Agabus congener, M.C — Species variabilis; Ovalis, 

 vel oblongo-ovalis, vix convexus, niger, elytris fuscescentibus, lateribus dilutioribus, 

 prothorace vix senescente lateribus angustius minus discrete ferrugineis, margine 

 laterali hand lato, antennis pedibusque rufis, his femoribus nigricantibus : prosterni 

 processu elongato, angusto, acuminate, nitido, impunctato, leviter transversim 

 convexo, baud carinato. Lonof. 7, lat. 4 m.m. 



The male has the front and middle tarsi rather elongate, their basal joints 

 distinctly incrassate, and furnished beneath with rather short hairs which bear 

 quite distinct palettes, tbe claws of the front feet are elongate and but little curved, 

 and very nearly simple, there being a scarcely visible sinuation of their lower edge. 

 In this sex the elytra bear only obscure traces of reticulation, while in the female 

 the sculpture is excessively variable ; sometimes the wing-cases in this sex are as free 

 from sculpture as in the male, while sometimes they are densely and distinctly 

 reticulate so as to render the surface dull ; the species also varies in colour, size 

 and form, and as the varieties are more or less localized in distribution thej^ lead 

 one to believe at first that they may be distinct species. In Scotland the females 

 are generally very dissimilar to the males, but one also finds rarely there specimens 

 which are intermediate in colour and sculpture between the males and the dissimilar 

 females. In Sweden, according to the few individuals I have seen from there, the 

 females are but little different from the Scotch intermediate form. On Monte Viso, 

 Ghiliani found a brightly coloured form looking just like Dytiscus paludosus, and 

 having the females similar in colour and sc\ilpture to the males ; while Doria has 

 found at Gnecco a large form in which the difierence between the sexes is carried 

 to its extreme. In the variety Gaurodjtes thomsoni (Sahl. Not. Fenn. XI, p. 407) 

 the form is usually narrower and more elongate, and the colour darker, and the 

 females have a slight reticulation near the humeral portion of the elytra. None of 

 the characters however are constant, and as the structural characters remain without 

 variation, I have been compelled to consider all these forms as belonging to but 



