Bolbochromus (Bolbochromus) tricostatus Selking, 2019

Selking, Ryan, 2019, A New Species of Bolbochromus Boucomont, 1909 (Coleoptera: Geotrupidae: Bolboceratinae) from Mindanao, Philippines, The Coleopterists Bulletin 73 (3), pp. 531-534 : 531-534

Bolbochromus (Bolbochromus) tricostatus Selking , new species

Zoobank.org/ urn:lsid:zoobank.org:act:1FE2253E-8F29-449C-AACC-2B039CFEAD2A ( Figs. 1–5 )

Type Material. Holotype, male: PHILIPPINES: Mindanao Is.: Lanao del Sur Province, Amai Manabilang Muni., 7.6813°N, 124.6513°E ± 4.5 km, VII.2018, local collector . Allotype, female: Same data as holotype. Paratype, female: PHILIPPINES: Mindanao Is.: Lanao del Sur Province, Maguing

Municipality, ca. 7.8903°N, 124.5236°E, X.2018, local collector. All types deposited in the Canadian Museum of Nature .

Description. Holotype male ( Figs. 1–3 ). Length 7.7 mm, maximum width at pronotum just before middle 4.5 mm. Body convex, dorsum glossy. Color: Head black. Pronotum with black along basal margin, widening towards middle until merging with 2 longitudinal parasagittal black bands; longitudinal black bands reaching anterior and posterior margins; middle of disc with central testaceous, heart-shaped macula, enclosed by longitudinal black bands; flecks of black present in lateral pronotal fova; lateral border black. Scutellum black. Elytra bicolored testaceous and black; sutural stria black along entire length; striae 4 and 7 partially black; area from interstria 7 to lateral edge of elytron black for distal 2/3; basal and lateral margins black to elytral apex. Head: Dorsal surface covered with coarse punctures, glabrous. Vertex of head with distinct, transverse tubercle, rounded apically. Frons along inner margins of eyes barely raised. Clypeus broadly arcuate anteriorly; middle of anterior margin with low tubercle; lateral margins of clypeus slightly raised just anterior to clypeogenal angles, which are nearly right angles. Margin of ocular canthus evenly arcuate; ocular canthus completely bisecting eyes. Labrum with anterior margin slightly concave; with fewer but larger punctures than remainder of head. Outer edge of mandibles evenly arcuate. Antenna testaceous, with 11 antennomeres, club elliptic, inner face of first antennomere of club with glabrous plate. Pronotum: Each lateral third with scattered large punctures, central third impunctate except anteriorly; smaller secondary punctures distributed along lateral margins, almost invisible micropunctures scattered across pronotum. Disc with distinctly impressed, median longitudinal groove terminating before reaching anterior and posterior margins, entire length with sparse punctures; triangular flat area with small punctures present in front of mid-longitudinal impression. Lateral foveae barely impressed, with several punctures. Anterior angles obtuse. Anterior and lateral margins with border terminating on basal margin at level of humeral umbone of elytra; lateral margins fringed with setae underneath, visible from above. Scutellum: Shiny, with extremely fine, nearly invisible punctures. Elytra: Each elytron with 13 punctate striae, all evenly punctate along their lengths; sutural stria runs parallel to scutellum and terminates at elytral base, interrupting stria 2 that ends before reaching elytral base; stria 5 ending before elytral base; striae 8 and 9 terminating on humeral umbone, not reaching elytral base; stria 10 extending around and below humeral umbone, longer than striae 8 and 9, not reaching elytral base; stria 11 terminating at elytral mid-length, well before elytral base; stria 12 extending to approximately same length as stria 10, not reaching elytral base; stria 13 with very deep punctures, situated in reflexed lateral margin of elytron, reaching elytral base. Reflexed lateral margin of elytra with setae of 2 lengths, thick setae sparsely and evenly scattered between punctures of stria 13, finer setae more densely distributed on either side of stria 13. Elytral interstriae slightly convex; surface appearing smooth, micropunctures almost invisible; interstriae 1, 4, and 7 distinctly more raised and convex than others; interstria 3 slightly more raised and convex in basal half than remaining interstriae. Elytral apices acuminate. Ventral face of epipleuron black, with single row of setae. Legs: Protibia with 9 teeth along outer margin, gradually increasing in size from base to apex, with distal 3 teeth much larger than preceding. Meso- and metatibiae each with 3 distinct transverse carinae on outer face, fringed with acuminate spines. Apical mesotibial spurs adjacent to each other, unequal in length, with inner spur shorter than outer spur; apical metatibial spurs subequal in length, spaced apart by basal width of a spur. Genitalia: Parameres ( Fig. 5 ) testaceous in color, with apical teeth darkened, elongate, each with slight transverse dorsal impression at mid-length and inwardly curved, contiguous series of teeth at apex; ventral side evenly convex.

Allotype female same as holotype except elytral interstriae 4 and 7 with less black coloration anteriorly; transverse tubercle of vertex slightly bifid; lateral margin of pronotum, when viewed ventrally, slightly wavy; inner metatibial spur slightly shorter than outer metatibial spur.

Variation. Bolbochromus tricostatus exhibits some color variation on the pronotum and elytra ( Fig. 4 ). The longitudinal black bands may be absent on the pronotum, with only the presence of a basal black area and traces of black bands extending posteriorly a short distance on the anterior margin. The amount of black on elytral interstria 4 varies from almost all of it being black to just a small region medially. The lateral black region of the elytra beyond interstria 7 also varies in how much of the elytral length is black. The frontal tubercle can range from being transverse to apically bifid as the holotype frontal tubercle is transversely rounded (presumably worn), and the paratype frontal tubercles are apically bifid.

Etymology. The species name “tricostatus” refers to the three distinctly raised interstriae on each elytron.

Diagnosis. When using the key in Krikken and Li (2013), B. tricostatus will key out to Bolbochromus mindanaicus Krikken and Li, 2013 when using pronotal coloration, and to Bolbochromus nigriceps (Wiedemann, 1823) when using elytral coloration. When using the key in Li et al. (2019), B. tricostatus will key out to Bolbochromus luzonensis Li, Krikken, and Wang, 2019 when using coloration, and to B. mindanaicus when using paramere length.

Bolbochromus tricostatus can be easily distinguished from its Pacific Island congeners by the presence of the distinctly convex elytral interstriae 1, 4, and 7. It can be further separated from the other species of the Philippines in that the parameres of the male genitalia are glabrous, parallel-sided, and apically adorned with inwardly curved denticles. In B. mindanaicus , the parameres gradually converge and are without apical denticles. In B. nigriceps , the form of the male genitalia is starkly different (compare figs. 52–53 in Krikken and Li (2013) to Fig. 5 ). In Bolbochromus hirokawai Ochi, Kon, and Kawahara, 2010 , the base of the parameres has heavy setation. Both B. hirokawai and B. nigriceps possess a non-bifid conical protrusion on the frons, whereas the frontal tubercle of B. tricostatus is transverse to slightly bifid. In B. luzonensis , the parameres are half the length of the basal piece, whereas in B. tricostatus the parameres are equal in length to the basal piece. In Bolbochromus setosifrons Li, Krikken, and Wang, 2019 , the frons possesses two long, robust setae laterad of the frontal tubercle, and the eyes are large dorsally, whereas in B. tricostatus the frons is glabrous, and the eyes are small dorsally. In Bolbochromus jengi Li, Krikken, and Wang, 2019 , the pronotum is sharply declivous anteriorly, whereas in B. tricostatus the pronotum is evenly convex from base to apex. The new species is provisionally endemic to the island of Mindanao.

Four Indian species of Bolbochromus also have three distinctly raised interstriae: Bolbochromus lineatus (Westwood, 1848) , Bolbochromus nigerrimus (Westwood, 1852) , Bolbochromus plagiatus (Westwood, 1852) , and Bolbochromus posticalis (Westwood, 1852) . These species can be separated from B. tricostatus by the following explanation (see table 1 in Krikken and Li (2013)). The pronotum of B. tricostatus is evenly convex from base to apex, whereas in its tricostate Indian congeners the anterior declivity of the pronotum is distinctly deplanate. In B. lineatus and B. nigerrimus , the frontal protrusion is non-bifid and conical whereas in B. tricostatus the frontal protrusion is transverse to slightly bifid. In B. plagiatus , the length of the body is over 8.0 mm, while in B. tricostatus the length is below 8.0 mm. In B. posticalis , there are five elytral striae between the humeral umbone and elytral suture, whereas in B. tricostatus there are seven elytral striae.

Figures

Figs. 1–5. Bolbochromus tricostatus. 1) Holotype male, dorsal view, scale bar = 4 mm; 2) Holotype, left frontolateral view; 3) Holotype, left lateral view; 4) Paratype female, left fronto-lateral view; 5) Holotype aedeagus, dorsal view.