396 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 117 



PlatydemaparvulumCa.sey,1884:,pTp. 50, 105. — Horn, 1885, p. 111. — Casey, 1890, 

 p. 485. 



Description. — Body broadly oval, moderately convex, black, shin- 

 ing. Head of male with two prominent, parallel, cylLtidrical, forward- 

 projecting horns between eyes, a deep depression between them; head 

 of female with sharply pointed tubercles instead of horns, depression 

 between them shallower, antennae and moiithparts reddish brown, 

 terminal segment of maxillary palpus short, broadly triangular; eyes 

 large, flattened dorsally, very deeply emarginate, separated ventrally 

 by a distance varying from 1 to slightly more than 2% times the 

 longer axis of one eye. Pronotum trapezoidal, strongly narrowed 

 from base to apex, sides nearly straight to slightly arcuate, basal 

 angles rectangular, apical angles narrowl}^ rounded, strongly deflected, 

 margmal bead rather fine, slightly reflected, set oft' from rest of pro- 

 notum by a very narrow flattened area which parallels it, surface 

 uniformly moderately, coarsely, and densely, punctured. Elytral 

 striae feebly impressed, finely and closely punctured, intervals dis- 

 tinctly convex, relatively coarsely and densely punctured. Prosternal 

 process horizontal and prominent. Ventral surface of prothorax usu- 

 ally thickened and convex, coarsely and densely punctured to almost 

 smooth; metasternum punctured at least on anterior two thirds, im- 

 punctate on posterior third or less. Basal three abdominal sternites 

 coarsely and densely, sometimes confluently, punctured, especially lat- 

 erally; apical two segments finely and sparsely punctulate. Male 

 genitalia with ventral portions of lateral lobes elongate, curved later- 

 ally, meeting the basal sclerite (pi. 4, figs. 22, 23). Measurements: 

 length 3.4-5.8 mm.; width 2.0-3.5 mm. 



Remarks. — -This is a widespread and common species and, as one 

 might expect, subject to considerable subtle variation, particularly 

 in sculpture and punctation. The most noteworthy variation is in 

 the distance separating the eyes ventrally, which caused considerable 

 consternation until a systematic study of series of specimens from 

 various localities was undertaken. From the accumulated data, it 

 was found that the species varies clinally in regard to this character. 

 In the northern part of its range, from New England west to ^linne- 

 sota and south to Ohio, Indiana, and Illinois, the eyes are separated 

 by a distance subequal, on the average, to about twice the longer 

 axis of one eye. This ratio dimmishes as one proceeds southward, 

 reaching its climax m northern South America, where the distance 

 separating the eyes is subequal to one eye. Roughly the same ratio 

 prevails in the West Indies. 



Champion (1886) considered all of his Central American specimens 

 to be conspecific with those from the United States. Specimens 



