706 On Aquatic Carnivorous Coleoptera or 'DjtisciduB. 



The species varies much in size and minute details, but I can see no signs of specific 

 distinction. It cannot be mistaken for any other. 



OhUi. 1100. 



1104. Cybister glaucus, Brulle, Tragus glaucus, M.C. — Ovalis, subdepresssus, 

 anterius angustatus, nitidus, Isevigatus, supra olivaceus, capite anterius parum argute 

 testaceo, thorace elytrisque lateribus jjIus minusve vage ferrugineo-tinctis ; subtus 

 vel piceus vel nigricans, pedibus quatuor anterioribus rufis, posterioribus vel ferru- 

 gineis vel nigris ; femoribus posterioribus angulo externo minutissime acuto vel 

 recto. Long. 28, lat. 16 m.m. 



The male front tarsi are small, attaining only 2 m.m. in the transverse direction ; 

 the intermediate tarsi have elongate sexual hairs on the basal joint, and also a few 

 on the extreme base of the following joint. The female appears to be quite with- 

 out sexual developments, but under a powerful lens traces of a rudimentary 

 sexual sculpture may generally be found, consisting of a very fine punctuation, 

 more or less mixed with excessively fine scratches, along the middle of the wing- 

 cases near the base. 



This species also appears to be a variable one ; there may be roughly said to be 

 two forms, one in which the colour of the upper and under surface and the hind legs 

 are tinctured with ferruginous, and another in which the colour is nearly black 

 with olive reflections ; the former of the two forms generally has the apical angle 

 of the femora more acute, and the females have the sexual sculpture more obsolete 

 than in the other variety ; but these characters are variable and indicate no specific 

 distinction. 



South America ; especially in the south-east ; Buenos Ayres, Monte Video ; Bolivia {fide Mus. Castle- 

 nau). 1101. 



Group 2. 



1105. Dytiscus latus, Fab., Trogus lotus, M.C. — Ovalis, crassus, sat oonvexus, 

 saepe ad basin eljrtrorum subsulcatus, olivaceus, capite anterius vage ferrugineo ; 

 subtus niger, prosterno in medio olivaceo ; pedibus quatuor anterioribus rufo-obscuris, 

 posterioribus piceis : antennis parum gracilibus. Long, 22, lat. 13 m.m. 



The male has the front tarsi quite small, attaining only l\ m.m in the transverse 

 direction, their fringing hairs at the heel are short and placed very near the palettes 

 so that there is no pubescent area ; the iutei'iuediate tar.si have a narrow line of 

 quite short sexual pubescence along the underside of the basal joint, and there may 

 be traces of a similar line on the following joint; the inner claw on the hind feet 

 is much smaller and shorter than the outer one. The female has a sexual sculpture 



