Taxonomic notes on Lasioglossum (Lasioglossum) subopacum (Smith) and L. (L.) okinawa Ebmer et Maeta (Hymenoptera, Halictidae) from Asia

Abstract Lasioglossum (Lasioglossum) subopacum (Smith) is recorded from the Korean Peninsula for the first time. Lasioglossum (Lasioglossum) okinawa Ebmer et Maeta from Japan is ranked to a subspecies of Lasioglossum (Lasioglossum) subopacum judging from the characteristics of the male. The male of Lasioglossum (Lasioglossum) subopacum okinawa is described for the first time. Some bionomical notes of both subspecies are presented.


Introduction
The halictine bee subgenus Lasioglossum s. str. Curtis, 1833 (Halictidae: Halictinae) is morphologically characterized by the second submarginal crossvein of female fore wing as strong as the first, and the female inner hind tibial spur serrate or pectinate with five or more teeth. This subgenus is mainly known from the Holarctic Region with 111 species recorded in the Palaearctic Region. Two of them, Lasioglossum (Lasioglossum) subopacum (Smith, 1853) and L. (L.) okinawa Ebmer et Maeta, 1999 are known to occur in Asia: the former from eastern to southeastern Asia (Pesenko 2006), and the latter only from the Ryukyu Islands, southwestern Japan (Ebmer and Maeta 1999). The latter taxon was originally described based on only female specimens. In the course of my study of Asian halictid bee fauna, I have been examined extensive series of specimens collected particularly from eastern Asia. Through careful examination, I have found L. subopacum from the Korean Peninsula (South Korea) for the first time, as well as the previously undescribed males of L. okinawa. In addition, I found that the male of L. okinawa cannot be clearly separated from L. subopacum, so I concluded that L. okinawa should be properly treated a geographical race, a subspecies of L. subopacum. In the present paper, I report the new taxonomic notes of L. subopacum including the male description of L. subopacum okinawa and some bionomical notes of both subspecies.

Material and methods
This study is based on the specimens deposited in the following institutions, which are referred to in the text by the following abbreviations: ELKU, Entomological Laboratory, Faculty of Agriculture, Kyushu University, Fukuoka, Japan; EBSU, Prof. Emeritus Yasuo Maeta's collection, deposited in the Division of Environmental Biology, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan; BPBM, Maa's collection borrowed from the Bernice P. Bishop Museum, Honolulu, Hawaii, USA; MNHAH, the late Dr. Shoichi F. Sakagami's collection, deposited in the Museum of Nature and Human Activities, Hyogo, Sanda, Japan; and without acronym, my private collection, now deposited in the ELKU.

Taxonomy
Lasioglossum ( Diagnosis. This species is divided into two subspecies, one of which is newly relegated to a subspecies of Lasioglossum subopacum as treated below. The nominotypical subspecies is separated from the ssp. okinawa by only the female characteristic that propodeum, and T1 basally with dense and thick yellowish tomentose as in Figs 20, 22. In male, both subspecies cannot clearly separate. This subspecies is separated from the other Korean Lasioglossum s. str. species in having the combination of following characters: the mesoscutum reflexed upward in both sexes and densely transversely rows on medio-anterior margin in female; the female propodeum and T1 with dense yellowish tomentose; the shape of hair tufts on male S6 and the gonostylus as in Fig. 11 [ Diagnosis. This subspecies is separated from the ssp. subopacum by the female propodeum and T1 basally with sparse and thin whitish tomentose as in Figs 21, 23. In Japan, it is closely similar to Lasioglossum (Lasioglossum) occidens (Smith, 1873) and L. (L.) sakishima Ebmer et Maeta, 1999. However, it is separated from the former by the mesoscutum reflexed upward in both sexes and densely transversely rows on medioanterior margin in female, the T1 basally with whitish tomentose tufts in both sexes (Figs 6, 23), the shape of hair tufts on male S6 (Fig. 15), and the gonostylus narrowly rounded apically as in Fig 10; from the latter by the basal elevation of male labrum broadly rounded (Fig. 14), the sculpture on female mesoscutum as stated above, the shape of both hair tufts on male S6 and gonostylus. In contrast, in L. occidens, mesoscutum flat in both sexes and densely coarsely punctate on medio-anterior margin in female, T1 without tomentose hair tufts in both sexes as in Fig. 16, hair tufts on male S6 as in Fig. 17, and gonostylus broadly rounded as in Fig. 12; in L. sakishima, basal elevation of male labrum small and rounded as in Fig. 18, female mesoscutum reticulate-punctate on anterior margin, shape of hair tufts on male S6 as in Fig. 19, and gonostylus truncate apically as in Fig. 13. Description of male (new to science). Body length 7.0-8.7mm, wing length 6.0-7.1mm (n=5).
Color. Body black except on the following parts: mandible apical half reddish brown; tegula blackish brown translucent; tibial spur yellow; posterior margin of metasomal terga narrowly brown translucent. Wings nearly transparent; veins and pterostigma blackish brown.
Pilosity. Mostly whitish; pale brown on mesosoma dorsally; mesoscutellum and metanotum mixed with blackish brown hairs. Head with sparse short fine branched hairs, and mixed with moderately dense tomentose on lower paraocular area. Hairs on mesosoma finely branched except on the following parts: dorsal, lateral surface, and around lateral lobe of pronotum with dense tomentose. T1 (Fig. 6) basally with a pair of tomentose tufts, however sometimes disappear. Disc on T2-5 with moderately dense short and simple hairs. Basal hair bands on metasomal terga present on T2-4 or T2-3. Apical fimbriae on metasomal terga absent. Acarinarium absent. S6 with well-formed, distinctive hair tufts as in Fig. 15. Structure. Head nearly as long as wide; head length/width ratio 1.0-1.01 (n= 5). Vertex flat medially. Distance between lateral ocelli nearly as long as that between lateral ocellus and compound eye. Frons and paraocular area with reticulate-punctate, dimly shiny. Supraclypeal area slightly convex in lateral view, dimly shiny, with reticulate-punc- tate; IS with distinct tessellation. Clypeus 1.5× distance between lower rim of antennal socket and upper margin of clypeus; nearly flat, with moderately dense PP; IS nearly smooth. Basal area of labrum 2× as wide as long; basal elevation weakly developed, broadly rounded; distal process absent; labral fimbriae acutely pointed at apex. Mandible edentate. Hypostomal carina moderately developed; its anterior angle obtuse. Postgena slightly depressed, with distinct lineoration. Scape length 0.5-0.6mm (n= 5), F2 2.2× F1.
Metasomal terga with oily-dull luster. T1 with weak lineolation over entire surface, medially and apically with dense PP. T2-3 with dense PP over entire surface; IS weakly lineolate over entire surface. T4-5 similar to IS of T2-3. S7-8 (Fig. 7): S7 with short and slender median process; S8 without median process. Male genitalia as in Figs 8-10. Gonobase ventral arm ring-shaped, and not connected to each other at apical ends: bottom nearly flat. Gonocoxite smooth. Gonostylus simple and flat, butter knife-like apically. Ventral retrorse lobe absent.