On Aquatic Carnivorous CoJeoptera or Di/tisckJce. 691 



I. 73.— Genus RHANTATICUS. 



Coxal lines obliterated, so that no supra-articular border is visible, middle femora 

 with quite short spinuies. Elytra yellow speckled with black, the black specks 

 being more or less coalesced to form two or three irregular transverse black fascia. 



A single species* is known; it has a wide distribution in the warmer parts of the 

 eastern hemisphere. 



1083. Hydaticus signatipennis, Lap., M.O. — Ovalis, fere angustus, parum con- 

 vexus, Isevigatus, nitidus, testaceus, capite prothoraceque anterius et posterius in 

 medio nigro-signatis, elytris nigro-irroratis, irrorationibus in fascias duas, una ante 

 altera post medium, condensatis. Long. Ol, lat. 5 m.m. 



In the male the anterior tarsi are large, and clothed beneath with well developed 

 palettes; the more basal one of the three larger of these is distinctly larger 

 than the other two, which in fact are about intermediate between it and the smaller 

 ones ; the middle tarsi are not incrassate, but the three basal joints bear beneath 

 two rows of small sessile palettes. 



The species is the smallest of the Hydaticides, and has much resemblance to a 

 Rhantus; it varies in the extent of the black marks on the head and thorax, these 

 are usually more largely developed in the individuals from Australia and New 

 Caledonia than in those from other localities. In what may be called the type form 

 (fi-om tropical Asia) the vertex is black and the black colour extends forward along 

 the inner side of the eye, while on the middle of the head there are two black marks 

 placed at an angle to one another, and often joined so as to form a single angular 

 mark; on the thorax the black marks in front and behind have but a small extension 

 even in the lateral direction, and in some individuals the anterior one entirely 

 disappears : in the Australian individuals there is an additional black transverse 

 mark on the head in front of the other two, and in front of the basal mark of the 

 thorax there is another black mark, which however is joined to the basal mark in 

 the middle and at the sides so as to form a single transverse mark enclosing two 

 yellow spots, which however are sometimes absent owing to the still greater exten- 

 sion of the black colour. I can find no other characters to distinguish this form 

 and can scarcely think it constitutes a distinct species. In the Australian form the 

 hind tibijB and tarsi are more or less black. The individuals from Madagascar .show 

 a reproduction of the markings of the Australian race but in a far less constant 

 manner, and they have not the hind tibiae and tarsi dark, their form is shorter and 

 the black fasciae of the elytra less distinct than in the Australian individuals ; the 



* It is probable that H. congestus, Klug, (No. 1309 huj. op.) from Madagascar, is either a variety of this 

 species or a closely allied one. 



TRANS. EOT. DLB. SOC, N.S., VOL. n * U 



