666 On Aquatic Carnivorous Coleoptera or Dytiscada. 
signaturisque frontalibus, hoe plaga parva basali, nigris ; elytris ex parte majore 
nigris, lineis tribus testaceis ad basin plus minusve distinctis, margine late 
irregulariter testaceo, nigro-irrorato; antennis pedibusque anterioribus rufis, 
pedibus posterioribus piceis. Long. 143. lat. 8 m.m. 
The male tarsi seem scarcely to differ from those of Hydaticus capicola (No. 
1043), the female seems at first to possess no peculiar sculpture, but there exists 
on each side of the thorax an indistinct patch of very fine and dense sculpture. 
The species seems to be a very variable one in size and colour, indeed in this 
latter respect it is not easy to find two indviduals quite similar ; sometimes the 
black marks on the middle of the head are well developed, at other times nearly 
entirely absent; there is always a blackening of the base of the thorax in front of 
the scutellum, sometimes there is a more or less distinct, small dark mark on the 
middle of the thorax, and sometimes even the tront margin is a little blackened. 
The amount of black on the elytra varies greatly ; generally the sutural portion 
is entirely black except at the apex, the outer margin and apex are always yellow, 
dotted with black, the boundary between the black sutural part and the pale outer 
part is generally very irregular and indefinite; the black sutural part evidently 
arises from coalescence of the black dots, and in some cases it is absent, the elytra 
being dotted more or less regularly with black ; in this case the yellow longitudinal 
lines are distinct, but where the black colour is very largely developed these lines 
can only be distinguished at the extreme base. H. incaustus and H. isabelli, Aubé, 
are both varieties of this species. 
South America ; (Brazil, Columbia). 
1041. Hydaticus sobrinus, Aubé, M.C.—Ovalis, sat latus et convexus, subtus. 
piceus, prosterno testaceo, supra rufo-testaceus, capite, vertice signaturaque 
frontali et prothorace macula discoidali nigris, elytris creberrime nigro-irroratis, 
irrorationibus plus minusve condensatis, seepius fascia transversa post medium sat 
distincta, antennis pedibusque anterioribus rufis, pedibus posterioribus piceis. 
Long. 11%, lat. 62 m.m. 
This species is very closely allied to Hydaticus capicola (No. 1043), but is shorter 
in form, and has the legs shorter and stouter, the black mark on the thorax is. 
usually less extended in the transverse direction, and the black dots of the elytra 
are confluent in a more or less irregular manner. ‘The male characters are the 
same as in the two preceding species, and the female has.deep rug on the sides 
of the thorax as is the case in Hydaticus capicola. 
The amount of confluence of the black spots is variable ; nearly always an 
irregular black fascia behind the middle can be traced, but when the surface 
becomes very much blackened by extensive condensation, this fascia 1s, of course, 
less distinct ; the same remark applies to three yellow lines, or veins, on the 
