A Review of California Margarinotus Marseul (Coleoptera: Histeridae: Histerinae: Histerini), with Descriptions of Two New Species Author Caterino, Michael S. Santa Barbara Museum of Natural History, 2559 Puesta del Sol Rd., Santa Barbara, CA 93105, U. S. A mcaterino@sbnature2.org text The Coleopterists Bulletin 2010 2010-03-01 64 1 1 12 journal article 10.1649/0010-065X-64.1.1 1938-4394 4892928 Margarinotus ( Ptomister ) umbilicatus (Casey, 1893) ( Figs. 5A–D , 6 ) Hister umbilicatus Casey 1893: 545 . Margarinotus umbilicatus (Casey) ; Wenzel 1944: 126 . Fig. 6. Map of known California localities for Diagnosis. PEL= 3.74–4.55 mm ; PNW= 2.68– 3.18 mm . Margarinotus umbrosus and M. umbilicatus can be separated from most other California Margarinotus by the marginal pronotal stria, which is generally obsolete in the basal half or more. (This is also true of some individuals of M. sexstriatus , which is easily separated by its large size and nearly or fully absent fourth and sutural elytral striae.) These two species share dense, umbilicate propygidial and pygidial punctation, and generally have some denser pronotal punctures along the inner posterior edge of the inner lateral pronotal stria. Margarinotus umbilicatus can usually be separated from M. umbrosus by a more nearly complete outer lateral pronotal stria and denser lateral pronotal punctures. However, the two species cannot always be clearly differentiated, even by genitalia, because of an almost continuous range of variation between them. The median lobe of both species possesses dorsal subapical teeth. In typical M. umbilicatus there are two well separated teeth, nearly erect ( Fig. 5D ), whereas in typical M. umbrosus there is a trifid process, with a well developed median and relatively weak lateral teeth ( Fig. 5E ). On the other hand, a broad range of forms bridges these extremes, from basically bifid with a minor median tooth, to a nearly rectangular weakly trifid process ( Fig. 5C ), to one with three equally developed teeth. Generally, the umbrosus form, with the median tooth the strongest, predominates from the San Francisco Bay area northward, and Wenzel (unpublished) considered this the southern limit of its range. However, numerous individuals of M. umbilicatus throughout its central and southern California range exhibit a well developed median tooth, or the teeth become largely united into a dentate plate. This is more frequent and well developed in the northern part of its range, and in the San Francisco Bay area the two species may or may not be distinct. Margarinotus spp. Fig. 5. Margarinotus umbilicatus and Margarinotus umbrosus , median lobe of aedeagus. A. M. umbilicatus , dorsal view. B. M. umbilicatus , lateral view. C. M. umbilicatus , apical view of gonopore (variant). D. M. umbilicatus (typical form), apical view of gonopore. E. M. umbrosus , apical view of gonopore. F. M. umbrosus , dorsal view. G. M. umbrosus , lateral view. Remarks. The majority of specimens of this species have been taken from wood rat nests. In the northern part of the range, where specimens more closely resemble M. umbrosus , generalist records are more common ( e.g. rotting vegetation, dung, etc.) than in the south. Distribution ( Fig. 6 ). This species was described from Marin County, and Fall (1901) lists only this record. The species occurs throughout central and southern California from around Sacramento southward to San Diego. The northernmost definite records are from the Clear Lake region (Lake County).