Chrysolina angusticollis

Chrysolina angusticollis (Motschulsky, 1861) Figs 2, 3 A – J, 4 Apterosoma angusticollis Motschulsky, 1861: 23 (Japan, syntype in ZMMU). Chrysomela japana Baly, 1874: 171 (Hakodadi, Japan, syntypes in BMNH). Type material examined. Syntype • 1 ♀ (ZMMU), [Yellow card with no text] // Type // Apterosoma / angusticollis / Motch / Japan. [typed on a yellow card]. Measurements of syntype. HW 2.53 mm; PEL 8.76 mm; EL 6.86 mm; EW 5.70 mm; APW 2.74 mm; MPW 3.91 mm; PPW 3.69 mm; PL 2.43 mm. Additional material examined. Japan. Hokkaido: • 1 ♀ (SEHU), Mt. Yokotsu, Mt. Eboshi, near Hakodate, 19.IX.1959, K. Munakata leg., MUNAKATA Coll., SEHU JAPAN, 2019, TT 0000350; • 1 ♀ (SEHU), Osima, Penins., Sengen-dake; 4–6.IX.1970, M. Suwa leg., TT 0000348; • 2 ♀ (SEHU), Hakodate, Hakodate-yama, 20.VII.2015, H. Takizawa leg., H. Takizawa Coll., SEHU JAPAN, 2012 [typed on a green card], TT 0000336, 337; Aomori Pref.: • 1 ♀ (SEHU), Zyuniko, 22.VI.1970, A. Abe leg, TT 0000335; • 1 ♀ (SEHU), Shitsukari, Higashi-dôri vill., 13.VI.2003, Satoshi Araki leg., TT 0000349. Distribution (of Ch. angusticollis treated as Morphological group A, B and C: Unit A- 1, A- 2, B- 1, B- 2, C- 1, C- 2 and C- 3). Japan: Hokkaido, Honshu (Aomori Pref.). Remarks. Ch. angusticollis is most likely described from a monotype of a female. Species of subgenus Apterosoma are difficult to identify from external traits, and since the syntype is a single female, it is difficult to determine which units in the Ch. angusticollis species complex in northern Japan can be assigned to the name “ Ch. angusticollis ”. Each unit can be identified by their male genitalia, hind wings, distribution area and in some cases, coloration, elytral punctation, and body size. Males of most units can be reliably identified by the median lobes of their genitalia, while females can only be identified by the shape of their hind wings. Therefore, we attempted to identify them through the following two methods: Estimation based on type locality: As we mentioned above, Motschulsky (1861) recorded only “ JAPAN ” as the type locality in the original description, but according to Savitsky (2020), the species described by Motschulsky (1861), including Ch. angusticollis, were collected in the environs of Hakodate city (Oshima Dist., in the south of Hokkaido Isl.), or in the northern part of Honshu Isl. between Tokyo city and Tsugaru Strait by Mrs E. S. Goshkevitch in 1858 or earlier. The units distributed in the above-mentioned area are Unit B- 1, Unit C- 1 and Unit D, but Unit D is unlikely to be the relevant unit because it is only distributed in narrow regions of high altitude. Checking of the syntype’s external traits: First, we examined the elytral surfaces of the syntype and found microscopic surface structure. The units displaying this microscopic surface structure on the elytra in the female are morphological groups A, B, C, and EI: Units A- 1, A- 2, B- 1, B- 2, C- 1, C- 2, C- 3, EI- 1 and EI- 2 (Saitoh et al. 2008; Saitoh 2010, 2012). Next, we checked the shape of the hind wing of the syntype, which is expanded apically, pinched before the tip and expanded 2 / 5 length from the tip (Fig. 3 A). In Ch. angusticollis species complex in northern Japan, only units B- 1, C- 1, 2, 3 and D exhibit a hindwing shape that is pinched before the tip. We examined individuals with this hindwing shape that were found in the vicinity of the collection site, estimated using method 1 and found individuals with hindwings similar to this hindwing shape in several localities in Hokkaido and Honshu. In these units, we found some variation in hind wing shape, the tip of which tended to be shorter in Unit B- 1 and longer in Unit C- 1 and in the syntype. Based on the above results, we have determined that syntype is very likely the equivalent of Unit C- 1. Mochizuki and Tsunekawa (1937) recorded Ch. angusticollis from Korea for the first time, but this record is excluded here because it is not an appropriate distribution, assuming that Ch. angusticollis is treated as Morphological group A, B and C: Units A- 1, A- 2, B- 1, B- 2, C- 1, C- 2 and C- 3, as indicated above. Krivolutskaya and Medvedev (1966) recorded this species from Kunashiri Isl. for the first time. Later on, Dubeshko and Medvedev (1989) recorded this species from “ Amur region ” and “ South Kuriles ”. Subsequently the specimen from Kunashiri Isl. was identified by Bieńkowski (2007) as Ch. porosirensis. The record from the Amur region was first made by Jacobson (1893), although later he reexamined these specimens and described them as a new species Chrysolina (Anopachys) lineigera (Jacobson, 1901). Therefore, Ch. angusticollis is currently distributed only in Japan. According to Bieńkowski (2001), there is a specimen collected from Honshu, Yokohama as “ Additional specimens ”, but the record of Ch. angusticollis from Yokohama should be confirmed because we have not been able to find any other records or identify any specimens from that locality. We also checked the syntypes of Chrysomela japana Baly, 1874, the only junior synonym of Ch. angusticollis, and which units they correspond to. There are three specimens (one male and two females) of the syntypes of Chrysomela japana in BMNH, and according to Baly (1874), the first specimen (Fig. 4 A – C) was collected from “ Hakodadi ” by Mr Whitely in the Lewis Collection, the second specimen (Fig. 4 D – F) was collected from “ Japan ” by Mr Moor in the Baly collection, and the third specimen (Fig. 4 G – I) was collected from “ Manchuria ” by Mr Bowring. If the data on these labels is correct, the first specimens should correspond to Unit C- 1, but the second specimen is in a similar situation to the syntype of Ch. angusticollis, and the shape of the hindwing must be confirmed. As for the third specimen, it could possibly be the only record from China. We checked the shape of the hind wing of the second (Fig. 4 D – F) and third (Fig. 4 G – I) syntypes, and found that each is expanded apically, pinched before the tip, and expanded at 2 / 5 length from the tip (Fig. 3 I, J) as seen in Unit C- 1 We checked the elytral surfaces of these syntypes and found microscopic surface structure. Although we cannot state here whether Ch. angusticollis is distributed in China, we found that at least all syntypes of Chrysomela japana are extremely similar to Unit C- 1.