512 On Aquatic Carnivorous Coleoptera or Dytiscide. 
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 coxze 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 enescente lateribus angustius minus discrete ferrugineis, margine 
laterali haud lato, antennis pedibusque rufis, his femoribus nigricantibus : prostern1 
processu elongato, angusto, acuminato, nitido, impunctato, leviter transversim 
convexo, haud carinato. Long. 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, the 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 they 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 sculpture to the males; while Doria has 
found at Gnecco a large form in which the difference between the sexes is carried 
to its extreme. In the variety Gaurodytes 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 
