On Aquatic Carnivorous Culeoptera or Dt/ttscidce. 671 



certain individuals there are quite distinct short irregular impressions, while in other 

 cases there is in the same situation only a more dense and, perhaps, rather coarser 

 jjunctuation, while often there seems to be no departure from such punctuation as 

 exists in thu male. 



The species is easily recognised by the yellow vitta running parallel with the 

 outer margin of the wing case, and extending from the base to near the apex, but 

 not there attaining the suture ; and by the short additional humeral vitta : both 

 these stripes are subject to some variations, the elongate one is sometimes inter- 

 rupted, or broken up, and, very rarely, nearly entirely absent ; the outer yellow 

 stripe also varies somewhat ; it is often so confluent with the more elongate stripe 

 that the two have the appearance of one stripe enclosing a small humeral black 

 mark : this black mark may become more elongate so that the junction of the two 

 yellow stripes occurs only just behind the middle ; in other cases the short humeral 

 stripe does not join the inner stripe at all, but is terminated just before the middle. 



The species also varies somewhat in size and form : it has always the ciliae of 

 the hind margins of the joints of the posterior tarsi very largely developed, but even 

 this is subject to a little variation. The variations are to some extent, but only 

 slightly, dependent on geographical distribution ; the most marked instance of 

 which is that the specimens in which the short humeral yellow stripes on the wing- 

 cases remains quite ununited with the longer stripe, occurs chiefly in Australia : 

 similar individuals occur, however, in Siam and the Malay peninsula, and every 

 grade of intermediate character may be found. A variety from the Philippine 

 Islands has the inner yellow stripe represented only by a spot of that colour near 

 the apex of the wing-cases, the humeral stripe being on the other hand a little 

 longer than usual, this has been recently described as a distinct species (H. 

 bipunctatus, Wehncke). 



This species is very ^videly distributed in the South Eastern parts of the Old Worhl. Japan, 

 Mantchuria, Formosa, China, East India, Ceylon, Malacca, Siam, Java, Boi-neo, Sumatra, Celebes, 

 Philippine Islands, Labuan, Batchian, Menado, and Australia (North, South, and "West). 1044. 



1050. Hydaticus exclamationis, Aub^, M.C — Ovalis, sat latus et convexus 

 niger, capite anterius prothoraceque ad latera testaceis, elytris vitta elongata lateral! 

 testacea ; antennis pedibusque anterioribus testaceis, pedibus posterioribus piceis. 

 Long. 13i, lat. 8 m.m. 



This species difiers from Dytiscus vittatus, inasmuch as the short humeral stripe 

 of the elytra of that species is in the present one extended to the extremity of the 

 wing-cases, while the inner stripe is entirely wanting ; besides this the cilias on the 

 hind margins of the joints of the posterior tarsi are much shorter, and the fringing 

 hairs at the base of the anterior tarsi of the male are considerably longer than in 



