Maechidius bombycinus Prokofiev, 2022

Prokofiev, Artem M., 2022, New species and records of Maechidius Macleay, 1819 from New Guinea (Coleoptera: Scarabaeidae: Melolonthinae), Zootaxa 5205 (5), pp. 445-462 : 449-451

Maechidius bombycinus Prokofiev , new species

Figs. 3–4

Type material. Holotype, male ( Fig. 3A ): “ D. Neue-Guinea / Huon-Golf / Bukaua / Prof. Neuhauss S.” ( ZMHB).

Additional material examined. 1 female: “D. N. Guinea / Sattelberg” ( ZMHB) ; 1 female: “D. N. Guinea / Sattelberg XII.08 / Prof. Neuhauss S.” ( ZMHB) ; 1 female: “ Htld. V. Finschhafer I. 30 / L. Wagner S.” ( ZMHB) ; 1 female: “D. N. Guinea / 2.VIII.12 Hauptlager / Kais. Augustafl. Exp. / Bürgers S.G.” ( ZMHB) ; 1 female: “D. N. Guinea / Standlager a. Aprilfluss 19.-26.ix.12 / Kais. Augustafl. Exp. / Bürgers S.G.” ( ZMHB) ; 1 female: “D. N. Guinea 152 / Standlager a. Aprilfluss / 15.-17.ix.12 Kais. Augustafl. Exp. / Bürgers S.G.” ( ZMHB) ; 1 female: “D. N. Guinea 175 / Standlager a. Aprilfluss 8.-9.x.12 / Kais. Augustafl. Exp. / Bürgers S.G.” ( ZMHB) .

Description of the holotype. Total body length 6.3 mm, greatest width 3.0 mm. Reddish-brown, silky; antennae yellowish-brown; setation pale. Antennae 9-segmented, club 3-lamellate. Labroclypeus deeply emarginate anteriorly, its lateral margins deeply and regularly concave between anterolateral angles and canthus in dorsal view, sinuous in lateral view; anterolateral angles distinctly protruding, lobate, reflexed; canthus broadly rounded in dorsal view. Dorsal surface of labroclypeus densely and rather finely punctured, punctures annular, setigerous, setae adpressed, somewhat shorter than on frons. Underside of labroclypeus sparsely setose. Frons flat. Punctures on frons moderately large, dense, annular; intervening spaces narrow and microreticulate; setae long, of inequal length, subequal to diameter of corresponding punctures or up to 2 its diameters in length. Pronotum transverse, with anterior margin concave and slightly bisinuate, anterolateral angles strongly protruding, acute. Pronotum widest across middle, its sides slightly more convergent anteriad than posteriad; basal margin bisinuate, convex before scutellar shield; posterolateral angles obtuse. Lateral margins of pronotum indistinctly crenulate, with crenulae almost confluent and uncountable in anterior half, becoming more obvious in posterior half of their length; a long seta (about half-length of compound eye) present between every two crenulae. Pronotal punctures moderately large, annular; intervening spaces smaller than punctures, with microreticulate sculpture giving a silky appearance; punctures setigerous, with setae not surpassing diameter of punctures. Hypomeron separated from prosternum by low continuous carina bearing moderately long setae; antennal pockets weakly expressed. Punctures of hypomeron moderately large and sparse, annular; their setae probably completely worn; intervening spaces very delicately microreticulate. Scutellar shield densely and somewhat irregularly punctured, apically pointed; punctures slightly smaller than on pronotum; intervening spaces generally smaller than diameter of punctures, microreticulate. Elytra moderately widened posteriad, subtruncate apically, without longitudinal carinae. Punctures of elytral disc long and narrow, incision-shaped; intervening spaces generally larger than length of punctures, with conspicuous microreticulate sculpture giving a silky appearance. Setae on elytral disc adpressed, not surpassing length of corresponding punctures, becoming longer (up to 1.5 length of punctures) and more erect toward the sides and apex. Pygidium weakly convex, with large annular punctures, more sparsely arranged along mid-line; intervening spaces generally smaller than diameter of punctures (except along mid-line), glossy, with microreticulation obvious laterobasally only; setae semi-erect, ×1.2–1.5 diameter of puncture, becoming longer toward apical margin. Meso- and metasternum bearing moderately small annular punctures of similar sizes; intervening spaces variable, distinctly microreticulate; setae expressed in punctures on metasternal disc only, adpressed, variable surpassing diameter of punctures. Abdominal ventrites distinctly microreticulate between moderately large annular punctures arranged in transverse rows. Ventral profile of abdomen weakly concave. Protibia widened distally, with two longitudinal carinae dorsally, two conspicuous apical teeth and very poorly expressed basal tooth; protibial spur absent, but apical inner side of protibia forming an angular extension at place of spur ( Fig. 3B ). Metatibial spurs slightly inequal in length, almost straight, pointed. All tarsomeres ordinary. Tarsal claws with large pulvilli. Aedeagus and spiculum gastrale, as on Figs. 3C–F .

Females (tentatively referred). Total body length 6.0– 6.5 mm, greatest width 2.8–3.0 mm. Dark to pale reddishbrown, sometimes with greenish tint on dorsal head and pronotum in oblique light ( Fig. 4A ). Labroclypeus from weakly concave to almost straight anteriorly ( Figs. 4B–C ), its lateral margins weakly convex to weakly sinuous in dorsal and lateral view; anterolateral angles poorly expressed, obtuse, weakly reflexed; canthus broadly rounded in dorsal view. Microreticulate sculpture on pronotum and elytra less pronounced than in male holotype. Hypomeral carina less sharp than in male holotype. Elytral setae comparably longer and thicker than in male holotype, those near sutural joint grouping in double parallel rows in some specimens (maximal expression as shown on Fig. 4A ). No conspicuous elytral carinae, but some intervening spaces variably thickened in some cases. Protibia with two strong apical teeth and variably expressed basal tooth (but usually strong); protibial spur absent, with no angular extension at apical inner side of protibia ( Fig. 4D ). Metatibial spurs inequal in length, lower one almost straight, 1.5 longer than upper one, distinctly clavate; upper spur slightly curved, blunt but not expanded at tip. Tarsal claws with large pulvilli. Anal valvi comma-shaped, with rather long setae at their distal tips.

Remarks. Identification of the females is tentative and somewhat disputable.Although most of their differences from the male holotype are connected with the sexual dimorphism, the less pronounced hypomeral carina and less conspicuous microsculpture of the dorsal body may not be this case. Elytral setae trend to group in two to three double rows on each side along the suture in some females, reminiscent the pattern of M. nepenthephilus but more localized (cf. Telnov, 2020: fig. 65). Since no males associated with these females are known, they were not included in the type series and are provisionally referred to this species.

Differential diagnosis. Although this species is keyed to the couplet 19 in Telnov’s (2020) key, it is most similar and apparently closely related to M. lobaticeps Frey, 1969 from the opposed couplet. In contrast to M. lobaticeps , the new species has distinctly microreticulate, opaque and silky dorsal surface (vs. smooth and shiny in M. lobaticeps ). Nevertheless, the other characters in both species are very similar and the aedeagi show only slight differences: the parameres are more parallel-sided in dorsal view with more attenuated tips in the lateral view in the new species in comparison with M. lobaticeps ( Telnov 2020: figs. 649–651). Within the species with microreticulate dorsal surface, the new species is most similar to M. nepenthephilus Telnov, 2020 , but can be distinguished by more pronounced and lobate anterolateral angles of the male labroclypeus, elytral puncturation not forming the irregularly paired rows of punctures (at least in male), by less regular puncturation of the pygidium and shape of the parameres ( Telnov 2020: figs. 679–680).

Etymology. The species is named from the Latin adjective bombycinus, a, um (silky), in reference to the strongly opaque integument.

Figures

FIGURE 3. Holotype of Maechidius bombycinus Prokofiev, new species. (A) dorsal view; (B) protibia; (C) aedeagus, lateral view; (D) parameres, dorsal view; (E) spiculum gastrale, dorsal view; (F) ditto, lateral view. Scale bars: (A, B) 1.0 mm; (C–F) 0.5 mm.

FIGURE 4. Putative females of Maechidius bombycinus Prokofiev, new species. (A) dorsal view; (B, C) head, dorsal view (variations in shape of labroclypeus); (D) protibia. Scale bars: (A) 1.0 mm; (B–D) 0.5 mm.