666 On Aquatic Carnivorous Colroptera or Dytiscidcu. 



signaturisque frontalibus. hoc plaga |)arva basali, nigris ; elytris ex parte majore 

 nigris, lineis tribus testaceis ad basin plus tninusve distinctis, margine late 

 irregulariter testaceo, nigro-irrorato ; antennis perlibusque anterioribus rufis, 

 pedibus posterioribus piceis. Long. 14i. lat. 8 m.ra. 



'I"he male tarsi seem scarcely to difter from those of Hydaticus capicola (No. 

 1013), 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 tliis 

 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 front 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 sutui-al 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 inore 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. incaustusand H. isabelli, Aub6, 

 are both varieties of this species. 



South America ; (Brazil, Columbia). 



](»41. Hydaticus sobrinus, Aube, .M.C. — Ovalis, sat latus et convexus, subtus 

 piceus, prosterno testaceo, supra rufo-testaceus, capite, vertice signatura(]ue 

 frontali et prothorace macula discoidali nigris, elytris creberrime nigro-irroratis, 

 irroraticnibus plus minusve condensatis, ssepius fascia transvei'sa post medium sat 

 distincta, antennis pedibusque anterioribus rufis, pedibus posterioribus piceis. 

 Long. Ill, lat. 6l m.m. 



This species is very closely allied to Hydaticus capicola (No. 104.S', 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 bla.'k dots of the elytra 

 are confluent in a more or less irregular mannei'. The male characters are the 

 same as in the two preceding species, and the female has deep rugae 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 is, of course, 

 less distinct ; the same remark applies to three yellow lines, or veins, on the 



