Margarinotus (Ptomister) thomomysi Caterino, 2010

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 : 8-9

Margarinotus (Ptomister) thomomysi Caterino , new species ( Figs. 7–9 )

Types. Holotype male: “ Huntington Lake , Fresno Co., CALIF. 27 Jan. ’48” / “nest of Thomomys monticola 18 inches under partly frozen ground” “ L.G. Ingles 1665” / “ Margarinotus n. sp. ex. USNM ”; USNM . Paratypes: 2 females, 1 male: same data as holotype , one female gold coated for SEM; deposited in USNM, FMNH [ FMNH-INS 0000 032 072], SBMN [ CBP0099524 ] .

Diagnosis. This is a highly distinctive species among not only California Margarinotus , but in the genus as a whole. Its elytral striation is unique in being essentially complete (lacking only, like most species of Margarinotus , the inner subhumeral stria), with adjacent pairs of striae (1-2, 3-4, 5-sutural) tending to be joined in irregular basal (and rarely apical) arcs ( Fig. 7B ). The body shape, especially the prothorax, is elongate and relatively narrow. The pronotal ground punctation grades evenly into markedly denser punctation in about the lateral and anterior one-fourth ( Fig. 7C ). These characters are sufficient to separate it from at least all other North American Margarinotus . The aedeagus of M. thomomysi ( Fig. 8 ) is distinctive to the extent that it is very simple. Among native western Margarinotus , this species and Margarinotus fenderi Wenzel are distinct in having the apical portion of the median lobe simple, tubular, and lacking any apical process (and these two are essentially identical in aedeagal characters.) The adventive European M. obscurus , reported from Oregon ( Mazur 1997) is similar in this regard, but has longer proximal apodemes, and thin median armature nearly reaching the apex of the median lobe.

Description. PEL= 4.36–4.86 mm; PNW= 2.74– 2.93 mm. Head finely but conspicuously punctate; frons ( Fig. 7A ) slightly depressed behind medially sinuate frontal stria; epistoma elevated; labrum about two-thirds as long as wide; mandibles flat above, conspicuously punctate on all surfaces; antennal club oval, sutures straight, very slightly oblique. Prothorax ( Fig. 7C ) about two-thirds as long as basal width, sides convergent, weakly arcuate; marginal pronotal stria extending from behind eye around anterior angles, becoming obsolete near base; outer lateral stria continuous with anterior stria, complete, sinuate and close to margin in basal two-thirds; inner lateral stria complete, connected to anterior stria at front, becoming obscured by lateral discal punctures at base; pronotal disc finely, conspicuously punctate at middle, becoming more densely punctate toward front and sides; pronotum slightly depressed and punctate along basal margin. Prosternal keel with complete striae, keel slightly convex between; prosternal lobe subtriangular, blunt at apex, with complete marginal stria more deeply impressed near the base; disc of pronotal lobe more densely punctate toward sides. Elytra ( Fig. 7B ) with complete outer subhumeral stria reaching fully to elytral base, striae 1-5 complete, sutural stria nearly or fully complete; pairs of striae 1-2, 3-4, and 5-sutural tending to be connected by basal arches (often just arc of punctures); elytral disc with fine ground punctation. Mesosternum relatively long, about half as long as wide, with complete, deeply impressed marginal stria; mesometasternal stria fine but deeply impressed, continuous with lateral metasternal stria, which is uninterrupted posteriorly, curving to nearly meet metepisternum; meso- and metasternal discs finely punctate at middle, more coarsely so at sides. Protibia rounded, with 7-8 marginal spines borne on weakly projecting teeth. Propygidium ( Fig. 7D ) moderately densely punctate, the punctures separated by nearly their widths; pygidium slightly more densely punctate, with fine ground punctation interspersed.

Male median lobe ( Fig. 8 ) with short, thin proximal apodemes about one-sixth total median lobe length; apical portion of median lobe thin, oval in cross section, evenly curved, narrowed to near apex; apex lacking dorsal process; median armature borne on curved basal plate almost one-half armature length, dorsal arms subtriangular, with outwardly curved leading edge, and nearly straight trailing (dorsal) edge.

Remarks. This species was recognized as undescribed long ago by Wenzel (unpublished), and I use the name he intended for the species. His manuscript assigned this, along with the more northern M. fenderi and the Asian Margarinotus boleti (Lewis) , to their own subgenus, hypothesizing a close relationship among them. I am inadequately familiar with the Old World fauna to take any such formal action. The species is only definitely known from a single collecting event, in the burrow of a pocket gopher ( Geomyidae : Thomomys sp. ), collected in the Sierra Nevada of Fresno County ( Fig. 9 ), at about 2,134 m. One additional female from a different locality is excluded from the type series, but appears to be the same species: CA: El Dorado Co., 1 mi E Pacific House, 25-IV-1992, C.B. Barr, seining El Dorado ditch; EMEC.

Figures

Fig. 7. Margarinotus thomomysi. A. Frons, anterior view. B. Elytron, dorsal view. C. Pronotum, dorsal view. D. Pygidium, posterodorsal view.

Fig. 8. Margarinotus thomomysi, median lobe of aedeagus. A. Dorsal view. B. Lateral view. C. Apical view of gonopore.

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