Margarinotus (Ptomister) sexstriatus (J. L. LeConte, 1851)

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

Margarinotus (Ptomister) sexstriatus (J. L. LeConte, 1851) ( Figs. 9 , 10A–B )

Hister sexstriatus J. L. LeConte 1851: 163 .

Hister maritimus Casey 1916: 214 ; Ross 1937: 107. Synonym.

Margarinotus sexstriatus (J. L. LeConte) ; Mazur 1997: 95.

Margarinotus sexstriatus jacobianus (Casey) ; Mazur 1997: 95 (valid subspecies)

Diagnosis. PEL= 5.61–6.98 mm; PNW= 3.99– 4.80 mm. Margarinotus sexstriatus is easily distinguished by its generally large size and three (or fewer) complete dorsal striae on the elytron (in addition to the outer subhumeral). Its outer lateral pronotal stria is generally complete, though very close to the margin, and usually, in fact, merged with the marginal in about the anterior one-fourth. The protibiae are strongly 3- or 4-dentate, the apical tooth bearing 3 spines. The median lobe of this species ( Fig. 10A– B ) has a distinctive trifid apical process. Unlike that of M. umbrosus and M. umbilicatus , in M. sexstriatus this is borne at the apex, rather than distinctly proximad. The median lobe is flattened and slightly elevated along the lateral edges, and the median dorsal armature is borne on a curved basal platform.

Remarks. This species is highly varied in size and most characters of external sculpturing. Ross (1937) evaluated the status of two related Casey ‘species’, M. maritimus and M. jacobianus (as Hister spp. ), synonymizing the first of these outright, but upholding the latter as a valid subspecies. Though described from only San Diego, Ross (1937) considered most populations south of the southern end of the Central Valley to belong to M. sexstriatus jacobianus . These are supposedly characterized by a more deeply incised, transverse frontal stria and by a weaker third dorsal elytral stria. Although I am skeptical of its validity, there is insufficient material available from central and southern California to warrant a definitive conclusion.

Distribution ( Fig. 9 ). In California M.sexstriatus has been recorded from the Coast Ranges and Sierra Nevada, from the San Francisco Bay area southward. Its distribution extends east into central Arizona ( Ross 1937) and probably south into Mexico, at least in Baja California (a single record from Oaxaca in mainland Mexico is doubtful; Wenzel unpublished).

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.