Micronychus pardus ( Kazantsev, 2018 ) Motyka, 2019

Motyka, Michal, 2019, Male identification, generic classification and sexual dimorphism of Micronychus pardus (Kazantsev, 2018) comb. nov. (Coleoptera: Lycidae: Calochrominae), Zootaxa 4657 (1), pp. 177-182 : 179-180

Micronychus pardus ( Kazantsev, 2018) , comb. nov.

Calochromus pardus Kazantsev, 2018: 269 .

( Figs 1–4, 6–7 )

Material examined. 1 male, 2 females, Borneo, Sabah, Gunung Emas, km 53 road KK-Tambunan, 1650 m, Bolm lgt. ( LMBC) .

Type locality. Sabah prov., Banjaran Crocker Mts, Gunung Alab peak, 1650–1800 m .

Diagnosis. Micronychus pardus is the only calochromine species which has female with net-like structure formed by elytral pubescence ( Fig. 2 ). The male is yellow and black coloured and according to our knowledge, there is no other species described from the area that resembles M. pardus in coloration or in shape of the genitalia ( Fig. 4 ). Due to the identified polymorphism, we cannot exclude that some conspecific specimens collected at lower elevation might be differently coloured and they might have been earlier described as a different species. In addition, no comprehensive revision of Bornean Micronychus is currently available.

Male. Body 8.1 mm long, parallel-sided; head, antennae, thorax, abdomen and legs black, humeral part of elytra with small black patch, basal two-thirds of elytra yellow to orange, gradually lighter towards apex, apical third of elytra black, mandibles light brown ( Figs 1, 3, 6, 7 ). Head small, frons with prominent antennal sockets and sharp straight longitudinal median depression; whole head with dense pubescence, setae short. Eyes small, hemispherically prominent, frontal interocular distance 1.83 times longer than maximum eye diameter. Labrum sclerotised, frontal margin straight; mandibles slender, long, with slightly overlapping tips when closed, outer margin of mandibles basally with several long setae, incisor simple, apices acute; maxillary palpi slender, four-segmented, with long setae, palpomere 1 as long as palpomere 2, palpomere 3 shortest, palpomere 4 longest, basally as wide as palpomeres 2 and 3, flattened and pointed apically. Labial palpi three-segmented ( Fig. 6 ), similar in shape. Antennal tubercles prominent, separated with narrow, densely setose, flat area. Antennae 11-segmented, reaching half of elytral length; antennomeres 4–8 moderately serrate, with gradually smaller processes in apical part of antennae, antennomeres 9–11 filiform; scapus pear-shaped, pedicel short, antennomere 3 shorter than scapus, antennomere 6 longest, further antennomeres gradually shortened, antennomeres 8–11 subequal in length ( Fig. 1 ). Pronotum slightly transverse to subquadrate with deep median groove and two longitudinal, obtuse keels ( Figs 1, 6 ), pronotum 1.2 times wider than length at base, anterior angles widely rounded, posterior ones slightly projected to rounded. Elytra flat, with rounded humeri, elytron with four weak, apically indistinct costae, secondary costae absent, elytra covered with dense short pubescence. Legs slender, laterally compressed, tarsi five-segmented, tarsomeres 1–4 gradually shorter, tarsomere 5 longest, claws simple. Male genitalia trilobate; phallus slender, slightly longer than parameres; parameres densely punctuated, basally narrow, gradually wider from middle part to apex; internal sac sclerotized, rod-shaped; phallobase asymmetrical, with lateral process ( Fig. 4 ).

Redescription. Female. Body small- to medium-sized, 9.75–12.80 mm long, elytra widened posteriorly. Head, antennae, thorax, abdomen and legs black, only longitudinal costae present, covered with brightly coloured pubescence; transverse elytral ‚costae‘ marked by pubescence only, setae orange to yellowish-brown, false elytral ‚cells‘ black, mandibles dark brown ( Fig. 2 ). Head small, frons with prominent ridges above antennal tubercles and shallow longitudinal impression, whole head densely pubescent, setae short. Eyes small, hemispherically prominent, frontal interocular distance 1.9–2.0 times longer than maximum eye diameter. Labrum sclerotised, frontal margin rounded; mandibles slender, with slightly overlapping tips when closed, base with several long setae externally, incisor simple, apices acute; maxillary palpi slender, shorter than those of male, four-segmented with long setae, palpomere 1 as long as palpomere 3, palpomere 4 longest, bulbous, flattened apically. Labial palpi three-segmented. Antennal tubercles prominent, separated by narrow, densely pubescent, flat area. Antennae 11-segmented, compressed, reaching first quarter of elytral length; antennomeres 4–10 moderately serrate with gradually smaller terminal processes in apical part of antennae, antennomere 11 filiform; scapus pear-like, pedicel short, antennomere 3 shorter than scapus,. Pronotum transverse to subquadrate with deep central groove and two longitudinal obtuse keels ( Fig. 2 ), pronotum 1.1 times wider than its length at base, anterior angles widely rounded, posterior only slightly projected. Elytra with rounded humeri, covered with dense short pubescence, elytron with four weak apically indistinct costae, secondary costae absent, pubescence arranged in ‚false transverse costae‘ ( Fig. 2 ). Legs slender, laterally compressed.

Generic placement. All characters which define Micronychus , i.e., the sclerotized internal sac, antennomere 3 longer than antennomere 2, as they are described in the generic differential diagnosis above, are clearly present and, therefore, we propose Micronychus pardus ( Kazantsev, 2018) , comb. nov.

Distribution. Borneo, Crocker Range.

Measurements. Male: BL 8.1 mm, WH 1.9 mm, EL 6.55 mm, PL 1.1 mm, PW 1.3 mm, Edist 0.55 mm, Ediam 0.3 mm. Female: BL 9.75–12.80 mm, WH 2.25–2.90 mm, EL 8.25–11.10 mm, PL 1.35–1.65 mm, PW 1.5–2.20 mm, Edist 0.6–0.85 mm, Ediam 0.3–0.45 mm.

Remark. The sexual dimorphism is rarely observed in Calochrominae and this is only the second case where males and females differ in mimetic patterns. The first case was reported from Sumatra when two specimens of Micronychus were photographed in copula ( Fig. 1 in Motyka et al. 2018). Unlike the earlier example, the females of Micronychus pardus represent a single known species of Micronychus which mimics the reticulate elytral costae known in Metriorrhynchini . The longitudinal costae are present, although partly reduced in all Calochrominae and they are also preserved in M. pardus . The transverse costae are absent and detailed observation shows that transverse costae are completely absent also in M. pardus . Kazantsev (2018) stated in the description that they are present, but it is only an optical illusion caused by the coloration of setae and their position. Despite recent extensive research in Lycidae , there has not been reported such resemblance in any other Calochromini .

Figures

FIGURES 1–8. General appearance and diagnostic characters used for the species delimitation. 1. General appearance of M. pardus comb. nov., male, 2. General appearance of M. pardus comb. nov., female, 3. Male antennae, 4. Male genitalia of M. pardus comb. nov., 5. Male genitalia of Micronychus sp., 6. head of M. pardus comb. nov., 7. Pronotum of M. pardus comb. nov., 8. Pronotum of Calochromus glaucopterus. Scale bars (1–2) 2 mm, (3–7) 0.5 mm, (8) 1 mm.