306 GEO. H. HORN, M. D. 



and base arcuate, hind angles broadly rounded, surface smooth. Elytra oval, 

 nearly as wide as long, base on each side oblique, humeral angles distinct 

 but obtuse, sutural stria moderately long, finely impressed, surface smooth, 

 in the pale specimens sparsely punctulate when examined under a high 

 power. Body beneath sparsely punctulate. Length .08 — .10 inch; 2 — 2.5 mm. 

 (PI. VII, fig. 14). 



Male. — Anterior and middle tarsi slightly dilated. Tarsi 5 — 5 — 4. Left mandi- 

 ble either much prolonged or with a horn-like process from the upper side. 

 Female. — Tarsi slender 5 — 4 — 4. Mandibles similar not prolonged. 



After an examination of a large number of specimens I find that 

 the elytra are absolutely smooth in some and microscopically punctu- 

 late in others, the specimens which are totally black being the 

 smoother. The males also vary in the structure of the left mandible, 

 there being every gradation between the prolonged mandible and that 

 in which the prolongation becomes a distinct horn arising from its 

 upper edge. This variation can readily be shown in pulchrum which 

 seems to be abundant, and in this I have a male not diftering appreci- 

 ably in its mandibles from the female. As this mandibular character 

 is a normal structure which closely approaches the borders of mon- 

 strosity, its variation cannot be assumed to have specific value. 



A. parvulum Lee, seems to be merely a small form of the same. 



Occurs from Pennsylvania to Missouri, and from Canada to Kentucky. 



A. pulchrum Lee. — Resembles politum in form, elytra always distinctly 

 sparsely punctulate. Head piceous, often with a paler vertical spot. Thorax 

 reddish-yellow with large round, discal, piceous space. Elytra piceous, each 

 with two large, oblique, yellowish spots of variable size and shape. Length 

 .10— .12 inch; 2.5—3 mm. 



Sexual characters as in politum. 



The color varies greatly so that the head and thorax may be 

 entirely piceous and the elytral spots comparatively small, or the 

 spots may extend and become confluent. A. mandihulatum Mann., 

 is without much doubt the same species. 



Occurs in California and also in the White Mountains, New Hamp- 

 shire, (Austin), but I have not seen any from intermediate points 

 except Kentucky, (Dury). 



A. diflTorme Lee. — Similar in form to politum but a little more elongate, 

 piceous, moderately shining, margin of thorax and a vague oblique stripe on 

 each elytron. Head very obviously punctulate. Thorax sparsely and finely 

 punctulate. Elytra with sutural stria moderately deeply impressed and ex- 

 tending two thirds to base, surface sparsely but very evidently punctate. Body 

 beneath sparsely punctulate. Length .08 inch; 2 mm. 



Male. — First two joints only of anterior tarsus slightly dilated. Tarsi 5 — 5 — 4. 



Female. — Tarsi slender 5 — 4 — 4. 

 This species is so much more obviously punctate that there need 



