DIAPERINI NORTH OF MEXICO TRIPLEHORN 431 



arcuate from eye to eye, clypeus well defined, eyes moderately large, 

 convex, anterior margin broadly and deeply emarginate; separated 

 ventrally by from 1.6 to 2.3 times the longer axis of one eye; terminal 

 segment of maxillary palpus robust, broadly triangular; antennae 

 and mouthparts uniformly dark brown; dorsal surface of head very 

 coarsely and densely, sometimes rugosely punctured. Pronotum 

 transverse, sides strongly and evenly arcuate, convergent from base 

 to apex, apical margin feebly emarginate, basal margin feebly bi- 

 sinuate; scarcely margined but prominently beaded laterally; both 

 basal and apical angles obtuse, broadly rounded; surface uniformly 

 finely and densely punctured. Elytra nari'owly margined and feebly 

 undulate laterally, bead coarse and sharply reflected; discal striae 

 not impressed, punctm*es coarse and rather widely spaced; outer- 

 most stria gradually approaching adjacent one toward base, leav- 

 ing an unusually large, convex humeral interval between it and ely- 

 tral margin; scutellar striae absent; remaining striae normal, in- 

 tervals flat to feebly convex, moderately coarsely and densely punc- 

 tured; entire dorsal surface vdih short, microscopic setae arising from 

 punctures. Ventral surface of pronotum slightly concave, smooth; 

 prosternum narrow between coxae, broadly expanded and horizontal 

 caudally, apex acute, unusually deeply inserted into mesosternum; 

 mesosternum prominent mth narrowly V-shaped, elevated ridges; 

 metasternum coarsely and densely punctured medially, punctures 

 finer and more widely separated laterally; abdominal sternites 

 densely punctured medially, more coarsely and sparsely so laterally and 

 apically; fourth abdominal sternite always deeply impressed lat- 

 erally; other sternites sometimes also \vith. lateral impressions. Fem- 

 ora and tibiae concolorous wdth body, tarsi lighter, yello^\^sh browTi. 

 Male aedeagus (pi. 5, figs. 33, 34,) extremely large, apical sclerite 

 comprising only one-fifth the total length of aedeagus; penis prom- 

 inent, acutely prolonged and moderately well sclerotized apically. 

 Measurements: length 3.4-4.4 mm.; width 1.8-2.6 mm. 



Remarks. — This species, frequently credited to Horn, should be 

 assigned to Zimmerman. Horn published the description verbatim 

 from Zimmerman's manuscript after the latter 's death, clearly 

 giving him full recognition as author of the species. 



Considering the male genitalia alone, this species is probably the 

 most \videly divergent member of the genus Platydema to be found 

 in the Nearctic region. This divergence is further reflected in the 

 general appearance of the beetle. Superficially it most closely resem- 

 bles P. ruficolle, sharing in common with it, in addition to other charac- 

 ters, the absence of scutellar striae. The abnormally large humeral 

 interstrial elytral interval will immediately separate P. micans from 



