604 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



reticulatis, punctis seriatis conspicuis, ad apicem oblique truncatis, angulo externa 

 nullo. Long. lOj, lat. 5i m.m. 



The male has the basal joiuts of the front tarsi a good deal incrassate and com- 

 pressed, and furnished beneath with long hairs and with palettes, their claws are 

 elongate, sinuate, and unequal, the posterior being incrassate, and a little longer 

 than the front one, this latter being only moderately slender ; the middle tarsi have 

 the basal joints incrassate and greatly compressed, and clothed beneath in a manner 

 similar to the front ones ; the apical ventral plate is sinuate on each side, so as 

 to aj^pear produced in the middle, and this central part bears long deep rugge. In 

 the female this segment is but little sinuate at the sides, and the hinder part is 

 marked with moderately short rugae ; in this sex the elytra have on their basal 

 portion some short irregular scratches, which appear to vary in their number and 

 extent in dift'erent individuals. 



Chili. 866. 



916. Colymbetes prsemorsus, Er., Rhnntus varius, M.C. — Ovalis, sat elongatus, 

 angustulus, rufo-testaceus, pectore, (maris sed non feminte abdomine) verticeque 

 nigris, eljitris nigro-reticulatis, ad apicem truncatis, angulo externo rotundato ; 

 prosterno in medio crasse compresso-elevato. Long. 9, lat. ih m.m. 



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

 and furnished beneath with long hairs and with large palettes ; their claws are very 

 unequal the front one being slendei", moderately long, nearly straight, and very 

 acuminate, while the hinder one is a good deal longer and is thickened, sinuate and 

 acuminate, and has a jirojecting tooth close to the articulation ; the middle tarsi 

 have their basal joints much incrassate and compressed, and clothed beneath in a 

 similar manner to the front feet, their terminal joint is elongate, and bears long, 

 slender, nearly equal claws ; the apical ventral segment in each sex is deeply sinuate 

 on each side, and in the male is longitudinally strigose, but in a variable manner. 

 The female has numerous very short scratches on the elytra, and the serial punctures 

 are less distinct than in the male. 



The species is somewhat variable in colour ; besides the sexual disparity in the 

 colour of the ventral segments, there is also a variation independent of sex, the 

 breast being sometimes but little black, and occasionally in the male the black 

 colour does not entirely cover the ventral segments, while on the other hand in 

 certain females, the black colour is not entirely wanting ; the prothorax is some- 

 times blackish at the base, and occasionally lias traces of two black spots on the 

 disc. The size and the thickness of the hinder of the two front claws of the male 

 also vary somewhat. 



Soutli America, (Chili, Bolivia, Monte Video). 807. 



