694 On Aquatiz Carnivorous Coleoptera or Dytiscide. 
1087. Hydaticus adamsii, Clk., M.C.—Breviter ovalis, convexus, nitidus, subtus 
piceus, prosterno capiteque in medio testaceis, supra testaceus, vertice, signatura 
capitis mediali prothoracisque fasciis transversis marginalibus, nigris; elytris 
crebrius nigro-vermiculatis ; pedibus anterioribus testaceis, posterioribus nigris, 
fe mribus testaceis basi infuscato ; elytrorum epipleuris sat latis ; pedibus posterio- 
ribus brevibus, crassis. Long. 13, lat. 8 m.m. 
The male has three larger and about twenty-four smaller palettes on the front tarsi, 
and twelve on the intermediate feet, the latter being placed four on each of the 
three basal joints so as to form two perfectly regular longitudinal series ; the claws 
on each of these pairs are distinctly longer than in the female. There is also a 
difference in the extension of the thoracic coloration, the anterior band of black 
colour having in the female twice as great an extension in the antero-posterior 
direction as it has in the female ; the thorax of the female is a little shorter than it 
is in the male, and so it results that the yellow fascia intervening between the two 
black ones, is only about half as long in the female as it isin the male. In the 
female there is a very obscure development of sexual sculpture, towards the outside 
of the wing-case, consisting of scanty and not very distinct larger punctures. 
The species cannot readily be confounded with any other of the allies; although 
in the colour of the upper surface it somewhat resembles Dytiscus cinereus, it is at 
a glance distinguished therefrom by the more rotund form and by the dark colour 
of the undersurface ; moreover, the front border of the hind coxze does not extend 
quite so near to the middle coxal cavities. It apparently varies little; the ten- 
dency to corrugation of the surface of the thorax in the female is, however, more 
marked in some individuals of that sex than in others. 
Japan. 992. 
1088. Dytiscus cinereus, Linn., Hydaticus cinereus, M.C.—Ovalis, sat latus 
et convexus, nitidus, rufo-testaceus, capitis vertice signaturisque, et prothorace fasciis 
duabus magnis nigris, elytris creberrime nigro-vermiculatis ; elytrorum epipleuris 
angustis ; tarsis posterioribus sat gracilibus. Long. 14%, lat. 84 m.m. 
In the male of this species, the smaller palettes on the front tarsi are about twenty- 
eight in number, while on the middle feet the number is fourteen, six on the basal, four 
on each of the two following joints, placed in two perfectly regular longitudinal series. 
The female has no greater punctuation of the wing-cases than the male has. In 
this latter sex the thorax is rather longer than in the female so that the yellow 
space intervening between the anterior and posterior black bands is rather greater 
in the male than in the female. 
The anterior black band in this species always attains the front margin of the 
thorax, it is thus divided into two equal parts by the transverse series of punctures, 
and it is of about the same extension (in the antero-posterior direction) as the basal 
