Margarinotus (Ptomister) merdarius (Hoffmann, 1803)

Caterino, Michael S., 2010, A Review of California Margarinotus Marseul (Coleoptera: Histeridae: Histerinae: Histerini), with Descriptions of Two New Species, The Coleopterists Bulletin 64 (1), pp. 1-12 : 10-11

Margarinotus (Ptomister) merdarius (Hoffmann, 1803) ( Figs. 9 , 10C–D )

Hister merdarius Hoffmann 1803: 39

Hister memnonius Say 1825: 32 ; Erichson 1834: 143. Synonym.

Margarinotus merdarius (Hoffmann) ; Wenzel 1944: 126.

Diagnosis. PEL= 5.05–5.54 mm; PNW= 3.55– 4.11 mm. Margarinotus merdarius can be most easily recognized by the two complete lateral pronotal striae, the inner of which is strongly sinuate and deeply impressed in the basal half, approaching the outer stria at the base. The pronotum is relatively flat laterally, even appearing weakly reflexed posteriorly due to the deeply impressed striae. The striae of M. rectus are similar in general form, but are not deeply impressed, and the pronotum is evenly convex to the lateral margin. The median lobe ( Figs. 10C–D ), especially its apex, is distinctive, possessing a single reclinate dorsal process, recurved parallel to the median lobe; the median lobe itself is cylindrical, and narrowed from base to near apex, expanded slightly at the gonopore.

Remarks. This adventive European species seems to occur only in poultry houses in California ( Legner et al. 1975), and has not yet been reported from any native environments. It has been found throughout much of the state, including Alameda, El Dorado, Orange, Riverside, San Francisco, San Bernardino, San Luis Obispo, Santa Barbara, Sonoma, Stanislaus, and Ventura Counties (not shown). In its native range it occurs primarily in bird nests, as well as dung, fungus, and decaying vegetation (Wenzel unpublished).

Species not recorded from California

Figures

Fig. 9. Map of known California localities for Margarinotus spp.

Fig. 10. Margarinotus sexstriatus and Margarinotus merdarius, median lobe of aedeagus. A. M. sexstriatus, dorsal view. B. M. sexstriatus, lateral view. C. M. merdarius, apical view of gonopore. D. M. merdarius, dorsal view. E. M. merdarius, lateral view.