724 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



large almost triangular area, they do not quite reach to the lateral margin but 

 leave a narrow elongate space there smooth : the epipleurse behind ihe 

 shoulders are broad and flattened and obliquely perpendicular. 



The species varies a good deal in size and somewhat in the colour of the legs, 

 and often the epipleurte and metathoracic episterna are more or less rufescent : and 

 occasionally there may be seen in the male as well as in the female, the rudiments 

 of a second claw on the hind tarsus ; this claw is of short broad triangular form, 

 and is placed at the extremity of the inner terminal point of the unguicular cleft ; 

 in the female of C. binotatus this rudimentary claw appears as a slender elongate 

 process placed along the inner margin of the unguicular cleft. 



Aube has described as occurring in Senegal a species closely allied to C. owas, 

 and has called it C. bimaculatus; the characters he gives to distinguish the two 

 are quite without importance. 



I have a female specimen from Doue's collection, said to be from Algeria, and 

 this differs in no respect from large elongate individuals found in Madagascar. I 

 have also a male individual from Lake Nyassa, which is of decidedly more elongate 

 form than any specimen I have seen from Madagascar, and the patch of sexual 

 pubescence on the intermediate tarsus is only one-half the width of what it is in 

 the Madagascar examples. I consider it, however, only a variety of C. owas. In 

 the Munich Catalogue, Harold has proposed the name of Trogus caffer for the 

 Cybister binotatus of Boh. (nee. Klug), but it is doubtful whether Boheman's de- 

 scription indicates more than a female variety of this species. 



Madagascar. 1065. 



1136. Cybister immarginatus, Aube. — Gravidus, ovalis, latus, convexus, supra 

 nio-ro-olivaceus, prothoracis lateribus omnino vage et obsolete rufescentibus, subtus 

 niger, pedibus anterioribus et intermediis jjiceis femoribus basi apiceque, tibiisque 

 anterioribus scepius dilutioribus, pedibus posterioribus nigricantibus ; antennis rufis. 

 Long. 37, lat. 21 m.m. 



The male of this species has the front tarsi rather small, attaining only 2t — 3 

 m.m. in the transverse direction, the pubescent area is correspondingly small, and 

 the basal fringing hairs are short so as to project but little beyond the basal 

 pubescence. The intermediate tarsi have a rather large patch of moderately short 

 pubescence, the patch is narrowly oval in form, its basal termination being 

 particularly narrow ; their claws differ but little from those of the female. The 

 female has no trace of any sexual sculpture, and there is never the least rudiment 

 of a supplementary claw to the hind tarsi. 



The species varies a good deal in size and in colour, it is sometimes nearly entirely 

 black; at other times the metathoracic episterna are very rufescent, and other parts of 

 the undersurface also become more or less rufescent ; the largest specimens attain the 



