532 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



Mas, nitidus, elytris fusco-ceneis, elyti'orum reticulis sat elongatis. Long. 12 m.in. 



Fern., opaca, elytris fusco-sub-rutis, ad apicein sat nitidis, subtilius reticulatis, 

 reticulis elongatis, tantum ad apiceui latioribus et brevioribus. Long. 11 m.m. 



The male has the three basal joints of the front and middle tarsi incrassate, and 

 furnished beneath with glandular hairs, the outer portion of which bear about three 

 series of ill-developed palettes; the claws of both feet are rather elongate, equal and 

 simple : the sexual difference in sculpture and appearance is very striking. 



Though the species is approximated by the various varieties of Dytiscus bipus- 

 tulatus, yet on the whole it seems to me that it must be considered a distinct 

 species, until sufficiently intermediate forms can be brought forward. The simple 

 structure of the male tarsal claws, is a prominent distinctive character ; the female 

 is excessively close in appearance to the p var. (Agabus solieri, Aub^). of A. bipus- 

 tulatus, but it has not the sides of the thorax rounded ; in both sexes the prosternal 

 process is rather broader and flatter than in Dytiscus bipustulatus, approximating 

 to that of Agabus melanarius, Aube. 



Madeira. 806. 



751. Dytiscus bipustulatus, Linn., Agabus bipustulatus, M.C. — Species per varia^ 

 bills ; supra et infra undique strigulosus, niger, supra plus minusve senescens, 

 antennis palpisque rufis, pedibus piceis, anterioribus dilutioribus ; reticulis elytrorum 

 semper in parte basali longitudinalibus, s^epius angustis et elongatis. Long. 10, 

 lat. 5i 



The male has the three basal joints of the front and middle tarsi much incrassate, 

 and furnished beneath with glandular hairs, the outer portion of which bear about 

 three rows of ill-developed palettes; a considerable portion of the basal joint on 

 the front feet is bare. The anterior claws are unequal, the front one being moderately 

 long, and bearing a small tooth beneath at the extreme base, while the hinder one 

 is elongate and much dilated behind, the swelling extending over the greater part of 

 the length of the claw but leaving the extremity slender, and causing the outline 

 behind to be much sinuate : the claws on the middle feet are also unequal, both are 

 elongate and very little curved, the anterior one being considerably longer than the 

 other. There is generally a sexual difference in the sculpture of the upper surface 

 the female being duller than the male, and having the longitudinal strias finer and 

 denser, and on the humeral portion taking a more oblique outward direction, the 

 sculpture at the extreme apex is the same as in the male. 



This species which is perhaps the commonest of the European Dj'tiscidpe is 

 extremely variable as regards size, colour, form, sculpture, sexual disparity, and 

 the form of the male tarsi : the broad supra articular border readil\- distinguishes 

 it from the other European allies, except A. melanarius, Aube, and that species always 



