Diplocheila (Isorembus) obtusa (Le Conte 1847)

Diplocheila (Isorembus) obtusa Le Conte
Rembus obtusus Le Conte, 1848:420, [type specimen a female, in the Le Conte
Coll., MCZ no. 5706]. Type locality: Long's Peak (Colorado) determined
from original description). Diplochila obtusa Horn, 1880 : 52. Diplocheila obtusa Casey, 1920 : 200 and 205. Diplocheila parallela Casey, 1920:204 [type specimen a female, in Casey Coll.,
USNM no. 47383]. Type locality: Homer, Illinois; (determined from
original description). Rembus parallelus Lindroth, 1954: 136.
This species and the following one, D. undulata Carr, form a distinct unit within the striato punctata group, the distinguishing features of which are : pronotum with posterior angles distinctly and broadly rounded, anterior margin relatively deeply concave, and sides almost parallel (figs. 46 and 47). In addition, elytral interval 3 is usually impunctate. D. obtusa may be separated from D. undulata by the characters presented in the key.
Description. — Type, female. Long's Peak.
Length 10.5 mm., width 4.7 mm. Surface glossy, sculpture as described for striatopunctata group.
Frontal impressions of head small round pits. Eyes moderately convex, less so than in striatopunctata.
Pronotum with anterior margin relatively deeply emarginate (said by Le Conte to be shallowly emarginate but compared with the other species of the genus, the emargination is deep), sides slightly rounded, more strongly incurved anteriorly than posteriorly ; disc convex, declivous laterally, impressions average for group; posterior lateral impressions narrow, elongate (fig. 46).
Elytra with intervals flat, striae distinctly impressed, impunctate, stria 7 somewhat finer and shallower than 1-6. Interval 3 impunctate.
Retractile stylus not studied.
Variation.— Data on variation in total length, maximum width, and number of spines in the posterior median row of the hind tibiae are presented in tables 17-19. Frontal impressions of the head are broad and shallow, generally irregularly rounded in outline, although elongate in some specimens. The pronotum is usually as in the type, but the sides are more parallel and less strongly rounded in some specimens. The posterior lateral impressions attain the basal margins in a few specimens, but usually they are not that long.
The basal portion of stria 1 varies from completely absent to weak but visible, and never contacting the sutural portion of stria 1. Striae 1-5 are moderately deep in all specimens examined, 6 is slightly finer, and 7 is still finer. The elytral intervals vary from flat to slightly convex. Interval 3 is punctate in one specimen from Edmonton, Alberta.
The female stylus and median lobe of the male genitalia are like those of striatopunctata (1 male and 1 female dissected and studied).
Synonymical Notes. — The synonymy presented here was proposed by Lindroth ( 1954). The differences between the type of parallela and supposedly " typical " specimens of obtusa are characters that vary individually and are, therefore, not significant from a systematic standpoint. The slight size difference between the type of parallela (length
9.6 mm., width 4.4 mm.) and that of obtusa (length 10.5 mm., width
4.7 mm.) is not significant.
Distribution. — This species is transcontinental in the Northern Coniferous Forest — or at least along the waterways in this area, ranging northward at least to McMurray, Alberta (57° + N. lat. ), from British Columbia to Nova Scotia, southward in the east at least to Pennsylvania, in the middle west to southern Kansas (east of the 100th Meridian) and southward in the Rocky Mountains to New Mexico.
I have collected this species in Chautauqua County, New York and at McMurray, Alberta. In both areas the specimens were found under stones on moderately dry soil within twenty-five or thirty feet of a stream margin.
Thirty-six males and forty females collected in the following states have been studied.
Peripheral localities — Quebec: Como. Massachusetts: Plymouth County, Plymouth. Pennsylvania : Dauphin County, Harrisburg. New Mexico : Sandoval County, Jemez Mountains. Washington : Spokane County, Spokane Falls. Alberta : McMurray. Additional states and provinces — British Columbia. Colorado. Indiana. Iowa. Kansas. Michigan. Minnesota. Missouri. Nebraska. Nevada. New York. Ohio.

Diplocheila obtusa is a species of ground beetle in the family Carabidae. It is found in North America.