On Aquatic Carnivorous Coleoptera or Dytiscidce. 675 



the punctuation of the wing-cases is not so dense as in the typical individuals. 

 These characters become more or less modified in Californian specimens, and in the 

 broader and shorter individuals from this part of the Pacific district the resemblance 

 in form to Dytiscus fraternus is very great, and is accompanied by a great extension 

 of the black mark of the hind femora. A variety of this Californian race has, 

 however, the undersurface and hind femora entirely yellow. 



Crotch states that a form of the female without grooved elytra occurs, but I have 

 not seen such, the variation tending, when departure from the type is made, in the 

 direction of greater extension of the grooves, and I suspect that the individuals 

 alluded to by Crotch should have been rather referred to Dytiscus fraternus. 



The variations of the species, as given by Crotch, are : — 



Var. simplex, Lee. Posterior femora piceous, knees yellow ; female with the 

 elytra smooth. San Diego. 



Var. oregonensis. Elytra paler, more thinly irrorated with black, fascia paler and 

 more distinct, posterior femora pale. Oregon. 



Var. latiusculus, Lee. Testaceous beneath, sulci of $ as in type. 



Var. abbreviatus, Man., Aube. Larger, femora testaceous, sulci in the female 

 almost reaching the base. 



North America. Very -nddely distributed fi-om Sitka to Haiti. 958. 



1055. Dytiscus fraternus, Harr., Acilius fraternus, M.C. — Supra parum 

 convexus, testaceus, vertice prothoraceque signaturis transversis nigris, elytris 

 creberrime nigro-in-oratis fascia transversa pallida parum distincta, subtus pectore 

 abdomineque nigris, hoc minus testaceo-variegafco ; femoribus posterioribus nigri- 

 cantibus : corpore creberrime punctate ; antennis elongatis, tenuissimis. Long. 14, 

 lat. 8 m.m. 



Mas, subopacus, elytris creberrime punctatis. 



Fern., elytris sulcis latis, setulosis, ad basin valde abbreviatis, suturali paulo 

 breviore. 



This species has the male characters the same as in Acilius semisulcatus, except 

 that the three tufts of hairs on the intermediate tarsi are much less developed, and 

 appear indeed on a hasty inspection to be entirely wanting. 



The species is very closely allied to A. semisulcatus, but the anterior border of 

 the hind coxa is always separated by a longer space from the middle coxal cavity. 

 Besides this the species is usually rather broader, darker in colour, and more densely 

 punctured, and the furrows on the elytra of the female are more abbreviated in 

 front. A variety of this latter sex occurs in which the elytra are, like those of the 

 male, without grooves. 



The species varies somewhat in the colour of the upper surface, especially in the 



TRAXS. ROT. DCB. SOC, N.S., 'VOL. H. 4 g 



