Margarinotus (Ptomister) fractifrons (Casey, 1893)

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 : 5-7

Margarinotus (Ptomister) fractifrons (Casey, 1893) ( Figs. 3 , 4A–B )

Hister fractifrons Casey 1893: 543 ; Fall 1901. Hister planifrons Lewis 1908: 149 ; Wenzel 1960:

457. Synonym. Hister fidelis Casey 1916: 217 ; Wenzel 1960: 457.

Synonym.

Margarinotus fractifrons (Casey) ; Wenzel 1944: 126 [established combination]; Hatch 1962: plate 56 [illustrated].

Diagnosis. PEL= 4.61–5.92 mm; PNW= 3.30– 3.99 mm. This species is named for its most distinctive character. Its frontal stria is nearly always interrupted to varying degrees, from very narrowly near the middle to almost completely obsolete. Its pronotum has both lateral striae complete, the inner usually slightly sinuate behind the middle, and lacks any stronger lateral punctation. Most individuals also have fragments of the inner subhumeral stria visible in much of the apical half, usually as a discontinuous series of punctures, and the prosternal striae absent. The median lobe ( Figs. 4A–B ) of M. fractifrons is broadened and spoon-shaped, arching strongly dorsad toward the apex. Its sides are rounded, like those of M. pluto and Margarinotus mormon (Casey) . However, the median armature shape of M. fractifrons , lacking rounded ventral processes, distinguishes it from the former. The more evenly, less abruptly widened sides of its median lobe distinguish it from the latter.

Remarks. Margarinotus fractifrons is the most common Margarinotus in northern California, particularly in the Sierra Nevada. Populations east of the Sierra Nevada crest, in Inyo and Mono Counties, are slightly larger than average for the species, and have more irregularly impressed elytral striae. They otherwise fit the above diagnosis, and have typical M. fractifrons male genitalia. Rupert Wenzel (unpublished determinations) has previously considered these populations to represent M. mormon . I believe M. mormon to represent a synonym, or perhaps slightly differentiated subspecies, of M. fractifrons , although I have not seen sufficient material to take any definite action on its status at present. These populations should be re-examined in the context of a larger revision of this group.

Distribution ( Fig. 3 ). This species occurs from coastal British Columbia, Canada southward to central California. Within California most records are from the north coast ranges and Sierra Nevada. The southernmost records are from the backcountry of Santa Barbara County, in the Cuyama Valley. It has not been recently collected in that area despite fairly intensive efforts.

Margarinotus (Ptomister) harrisii (Kirby, 1837) ( Figs. 3 , 4C–D )

Hister harrisii Kirby 1837: 124 .

Margarinotus harrisii (Kirby) ; Wenzel 1944: 126.

Diagnosis. PEL= 4.17–4.98 mm; PNW= 2.93– 3.49 mm. The dense, conspicuous ground punctation of the pronotum and elytra will separate M. harrisii from all other California (and North American) Margarinotus (see figures in Bousquet and Laplante 2006). It has the outer lateral pronotal stria complete and the inner usually slightly abbreviated, or obliterated by denser lateral pronotal punctures. The propygidium and pygidium are densely covered with small punctures. The median lobe ( Figs. 4C–D ) is broadened and spoon-shaped apically, and deeply, but rather narrowly so. Its sides are nearly straight, and diverge only slightly toward the apex. The entire median lobe is strongly curved dorsad toward the apex. The median armature is short and rather simple, nearly triangular in lateral view, with the leading and trailing edges more or less straight. The genitalia is most similar to that of M. pluto and M. fractifrons , however, its median lobe is intermediate in width, and more deeply spoon-shaped than these. That of M. fractifrons is also clearly more broadly rounded.

Distribution ( Fig. 3 ). There are no previously published records for this species in California, although Wenzel (unpublished) recorded specimens from along the Oregon / California border and even as far south as Santa Cruz. The species was recently collected much further south in the San Bernardino Mts. (CBP0076400). These widely scattered records are the only ones known for the state. It is otherwise a very widely distributed species, ranging from coast to coast across the northern US and southern Canada (Bousquet and Laplante 2006), reaching its southernmost limit in California and Arizona. This species seems to prefer sandy, especially lacustrine situations ( Blatchley 1910; Wenzel unpublished), and this holds for the recent San Bernardino Mts. collection, though the species has also been reported from cow dung ( Blatchley 1910).

Margarinotus (Ptomister) rectus (Casey, 1916) ( Figs. 3 , 4E–F )

Hister rectus Casey 1916: 215 .

Margarinotus rectus (Casey) ; Wenzel 1944: 126.

Diagnosis. PEL= 4.92–5.11 mm; PNW= 3.43– 3.49 mm. Margarinotus rectus is most easily recognized by its elongate, relatively ‘rectangular’ body shape, although M. remotus , M. ephemeralis , and M. thomomysi may be nearly as elongate. It has both lateral pronotal striae complete, and the outer only slightly closer to the margin than to the inner. Both M. remotus and M. ephemeralis have only a single pronotal stria on each side, while M. thomomysi has all of the elytral striae complete. The aedeagus of M. rectus has a narrowly expanded, weakly spoon-shaped median lobe ( Figs. 4E–F ), with nearly straight, parallel sides. In this its median lobe is somewhat similar to that of M. harrisii , but is much narrower.

Distribution ( Fig. 3 ). This species is represented by a single California specimen, unfortunately a female, from Willits (Mendocino County). Wenzel identified this specimen with a question mark (unpublished), but it conforms in all external characters to what is a very distinctive species. Wenzel (unpublished) has also recorded specimens from the Oregon / California border to the north, and just east of Lake Tahoe in Nevada. It has been recorded as occurring in dung (Hatch 1962).

Margarinotus (Ptomister) pluto (Casey, 1893) ( Figs. 3 , 4G–H )

Hister pluto Casey 1893: 542 .

Margarinotus pluto (Casey) ; Wenzel 1944: 126.

Diagnosis. PEL= 5.54–5.73 mm; PNW= 3.86– 3.99 mm. In M. pluto the elytra are generally slightly lighter in color than the rest of the body, both lateral pronotal striae are complete, and the inner stria is bordered by distinct punctures mediad. Its frontal stria is generally recurved to a median point and the apex of the elytron has a transverse impression between striae 2 and 4. The median lobe of M. pluto ( Figs. 4G–H ) is broad, spoon-shaped, and strongly curved dorsad toward the apex. Its median armature is highly distinctive, with rather fine apical points and large rounded ventral processes.

Distribution ( Fig. 3 ). Bousquet and Laplante (2006) report this species as occurring in Oregon, and Wenzel (unpublished) reports a record from extreme northeastern California. I have seen three specimens from Modoc County (CASC). The species has been collected in the burrows of several mammals, including marmot ( Marmota Blumenbach ), badger ( Taxidia Waterhouse ), ground squirrels, and ‘gophers’ (possibly also referring to Spermophilus .)

Figures

Fig. 3. Map of known California localities for Margarinotus spp.

Fig. 4. Margarinotus spp., median lobe of aedeagus. A. M. fractifrons, dorsal view. B. M. fractifrons, lateral view. C. M. harrisii, dorsal view. D. M. harrisii, lateral view. E. M. rectus, dorsal view. F. M. rectus, lateral view. G. M. pluto, dorsal view. H. M. pluto, lateral view.