On Aquatic Carjiivorous Coleoptera or Dytiscidce 715 



Group 1. 



1119. Dytiscus fimbriolatus, Say, TiogusJimbnoIatus,M.C.— Oya.\is, supra niger, 

 subolivaceus, caplte anterius prothoraceque lateribus testaceis, elytris vitta lateral! 

 posterius obsoletescente testacea ; corpore subtus piceo, abdominis lateribus flavo- 

 maculatis, antennis pedibusque anterioribus rufis, pedibus posterioribus tarsisque 

 intermediis piceis. Long. 28^, lat. 16 m.m. 



The male has a narrow excessively obscure band of extremely short sexual 

 pubescence, on the undersurface of the basal joint of the intermediate tarsus ; and 

 the hind coxa has at the apex just iu front of the articulation three or four coarse 

 plicae. The female is without these folds ; but has a well marked sexual sculpture 

 on the upper surface, there are always some fine scratches on each side of the back 

 of the head, and the thorax has numerous irregular scratches, while the elytra are 

 generally covered with longitudinal scratches, anastomosing here and there, and 

 leaving only a small space at the apex, and a band along the suture smooth : the 

 epipleurae, just behind the shoulder, are broader than in the male, and are flattened, 

 and obliquely perpendicular, instead of being rounded, and transverse in direction, 

 as they are in the male. 



The species appears to be very variable, and it is quite possible that there will 

 prove to be more than one distinct form mixed under its name ; the yellow band 

 on the side of the elytra is rather narrow, and at the apex is indefinite, indeed on 

 the hinder half of the wing-case a line of darker colour separates the yellow line 

 from occupying the outer margin, this darker band is not often very definite ; at 

 the apex at a distance from the suture there are some yellow maculae, which when 

 more than usually distinct give to the yellow marginal band the appearance of 

 being dilated there. In a variety from Texas, the lateral band of the elytra is 

 broader, and reaches in a definite manner to the suture, where however it is 

 thinned out to a point. The sexual sculpture of the female also varies much ; the 

 scratches on the head are always present, and sometimes the scratches on the 

 thorax and elytra are coarse and close, while in certain individuals they become 

 finer, shorter and more isolated, and at the same time occupy a less area on the 

 wing-cases, their disappearance being from the apical and sutural portions. The 

 supplementary obsolete claw of the female hind tarsi also varies in its development, 

 being sometimes so small as to be not very easily detected, while in other cases it is 

 longer, more detached, and more conspicuous, it appears to be most largely deve- 

 loped in those cases where the terminal joint of the tarsus is shortest and thickest. 



Besides these points of variation, considerable difference is also found in size and 

 colour, and even in the extent of the development of the sexual pubescence on the 

 intermediate tarsi of the male, the band^on the basal joint being sometimes larger, 



TBAKI, HOT. DOB. SOC, M.S., VOL. U. * Z 



