0)1 Aquatic Carnivorous Coleoptera or Dytiscid(B. 913 



It is a perfectly distinct one, and would be very homogeneous, were it not for 

 Dytiscus liberus (No. 1,084), which departs considerably froiu the other species. It is 

 smaller than tlie other species, less convex, and has no black markings on the head 

 and thorax as the other species have ; it has moreover the middle legs more slender, 

 and their tibiae less spinulose, and the antennal portion of the head shorter, and 

 the setae of the middle femora shorter. In some of these points it makes an approxi- 

 mation to Rhantaticus. Some of the other species likewise depart more or less in 

 their structure from the average, thus Nos. 1,0S5, 1,086 and 1,087, have the front 

 border of the hind coxa not so near the middle one as the other species have : and 

 Hydaticus austriacus (No. 1,085), differs from the other species by the simple 

 middle tarsi of the male. 



I. 75.— Genus ERETES. {Vide p. 699.) 



Two closely allied species are all that exist to form this very distinct aggregate. 

 The .shape and colour are peculiar, and the skeleton is much softer than in most 

 other Dytiscidse. Rather flat above, and rather narrow, -the insect is a good deal 

 narrowed towards the front, the outlines of the thorax and elytra are very discon- 

 tinuous, and the eyes large and prominent. The whole insect is of a pale yellow, 

 or whitish colour, the head and thorax have two or three, incon.stant (sometimes 

 absent) transverse dark markings, and the elytra are more or less densely marked 

 with very distinct isolated punctures, each of which is black, and there may be a 

 transverse irregular black fascia before the apex ; this is sinuate so that the suture 

 projects slightly there. The head in front of the eyes is extremely reduced. The 

 pro thorax has a very fine elevated lateral margin. The prosternum is very reduced 

 in front of the coxae, but the inter-coxal portion is much thickened, the prosternal 

 process in which it terminates is rather narrow, gradually acuminate towards the 

 apex, and obsoletely margined. The hind coxae are enormous, so that the meta- 

 sternum which is elongate in the middle, is reduced at the sides to a very short, 

 parallel-sided, curved lacinia or wing, which is greatly deflexed round the anterior 

 border of the coxa, and is a little dilated near its rounded termination ; this termina- 

 tion is placed far from the epipleura, and the coxa is prolonged behind it and the 

 metathoracic episternum as far as the epipleura, while intervening between the edge 

 of the epipleura, the outer hinder edge of the episternum and the upper terminal 

 border of the coxa, there is seen very distinctly a triangular piece, which is a portion 

 of the metathoracic epimeron left uncovered by the very reduced epipleura : the 

 posterior margin of the coxa becomes thickened in a peculiar manner near its termina- 

 tion, so as to mark off the outer portion as a triangle separated from the larger 

 part by a thickened raised line : the coxal lines are fine, short and abbreviated in 

 one, obsolete in the other species ; the coxal lobes, are very short, rather broad, 

 without supra-articular border. The hind legs are rather slender, their tarsi are 

 elongate, the basal joint being not greatly shorter than the tibia, they are terminated 



