DYTISCID^E. 75 



DESCRIPTION. 

 (? 



Body reddish-yellow underneath, above olive-black. Head minutely but thinly punctured ; mouth, 

 nose, and antennae yellow; there is a red angular spot on the vertex: prothorax obsoletely channelled, 

 minutely and thinly punctured, with the limb widely yellow, but less so behind where the yellow 

 sends two teeth iuto the black disk ; an anterior and posterior transverse line of larger punctures are 

 also visible : scutellum wholly black : elytra with two discoidal longitudinal rows of punctures ; three 

 others, in which the punctures are more distant and less conspicuous, are interposed, one between 

 the suture and the first row, the next between the first and the second, and the third between the 

 second and the lateral margin ; there are besides a few scattered and very minute punctures ; at the 

 apex these rows are all lost in a number of scattered punctures intermixed with punctiform impres- 

 sions ; the side of the elytra, the external half of their base, and an oblique gleam at the apex are 

 all yellow, which colour though occupying a considerable breadth of the side, at the base and apex 

 is a narrow strip : 3 the sutures of the breast and margins of the ventral segments of the abdomen 

 are black or dusky ; scapulars rather thickly, deeply, and confluently punctured ; lateral angles of the 

 mesostethium wrinkled ; posterior dilated ; coxeb thinly punctured, legs yellow ; the lobes of the 

 metasternum are acuminated as in D. circumflexus. 4 



? 



The female differs from the male, in having the yellow parts redder, especially on the under-side 

 of the body ; the head and the prothorax are more thickly and distinctly punctured ; the angular 

 red signature of the vertex reaches the red spot between the eyes and the nose ; the elytra are 

 ploughed out into ten deep furrows, the external ones being the widest, there is also a very short 

 one between the sixth and seventh at the base ; these furrows approach the end of the elytrum, and 

 most of them terminate in a series of punctiform impressions which nearly reach the tip ; the eighth 

 and ninth furrows are shorter than the rest, and included between the confluent ends of the seventh 

 and tenth ; the whole elytrum is thickly and visibly punctured ; the scutellum is piceous : the 

 mesostethium is black with a large anterior yellow spot; the sutures and the margin of the seg- 

 ments are more widely and distinctly black than in the male. 



I at first regarded this as a variety of D. marginalis, and it is probably the species to which 

 Linne refers as found in North America: but upon a close examination I am convinced that D. 

 Ooligbukii, though the representative of that species, is not synonymous with it. The lobes of the 

 metasternum which terminate in a long acumen like those of D. circumflexus sufficiently prove this; 

 the prothorax of the male is shorter and more distinctly punctured, and the elytra less so. The 

 female has a little furrow between the sixth and seventh, not in D. marginalis ; the furrows are 

 all parallel, and fall short of the apex one third of the length of the elytrum — other more minute 

 differences are also observable. 



As this species was taken by the useful, worthy, and honest Esquimaux Ooligbuk, I trust I may 

 be excused for giving to it his name. 



3 If the elytra are rubbed hard, the black colour comes off and leaves the yellow. 

 * Curtis, Brit. Ent. iii, t. xcix,f. c. 



L 2 



