Physatocheila distinguenda (Jakovlev, 1880)

(Figs. 8C, 9C, 10C, 11C, 17E, 18E)

Monanthia (Physatocheila) distinguenda Jakovlev, 1880: 139 . Holotype: macropterous ♀, Russia: “Sarepta” [= Krasnoarmeysk, near Volgograd]; ZIAS.

Stephanitis salicorum Baba, 1925: 3 . Lectotype by subsequent designation (Tomokuni 1994: 842): macropterous ♀, Japan: Honshu, Nagano Prefecture, “Entoku-mura, Shimotakai-gun” [= Mitsuwa area of Nakano-shi]; ELHU. Synonymized by Golub (1977a: 29).

Physatocheila hailarensis Nonnaizab, 1985: 226 . Holotype: macropterous ♀, China: Inner Mongolia, Hulunbeir League; BDNU. Synonymized by Golub (1988a: 54).

Physatochila distinguenda: Horváth (1906: 96) (new combination); Kiritshenko (1951: 252) (key to species); Drake & Ruhoff (1965a: 332) (catalog); Putshkov (1974: 264) (monograph); Golub (1977a: 27) (distribution); Golub (1977b: 248) (distribution); Péricart (1983: 445) (monograph); Golub (1988b: 144) (key to species); Miyamoto & Yasunaga (1989: 167) (checklist: Japan); Tomokuni (1994: 842) (type specimen); Péricart & Golub (1996: 54) (checklist: Palaearctic); Kwon et al. (2001: 194) (checklist: Korea); Japanese Society of Applied Entomology and Zoology (2006: 56) (pest); Maehara (2010: 132) (distribution); Vinokurov et al. (2010: 158) (checklist: eastern Russia); Yamada & Tomokuni (2012: 199) (monograph); Nozaki & Nozaki (2013: 30) (distribution); Yano et al. (2013: 25) (distribution); Maehara (2014: 60) (distribution); Nakamura (2014: 358) (distribution); Yamada & Ishikawa (2016: 432) (checklist: Japan); Notsu & Watanabe (2020: 2) (distribution); Cho et al. (2020: 741) (checklist: Korea).

Monanthia salicorum: Takeya (1930: 67) (new combination); Takeya (1951: 22) (checklist: eastern Asia); Miyatake (1958: 15) (distribution); Hasegawa (1960: 45) (distribution).

Dictyla salicorum: Drake & Ruhoff (1960: 51) (new combination); Drake & Ruhoff (1965a: 195) (catalog); Tomokuni (1979: 137) (distribution).

Cysteochila salicorum: Lee (1967: 108) (new combination); Lee (1969: 195) (nymph, male genitalia); Japanese Society of Applied Entomology and Zoology (1980: 24) (pest); Miyamoto & Yasunaga (1989: 167) (checklist: Japan).

Specimens examined. Non-types (5 ♂♂ 8 ♀♀ 1 terminalia missing), JAPAN: Honshu: Tochigi Pref., Utsunomiya City, Higashikinoshiro, 30.iv.2008, leg. S. Maehara (1 ♀, TUA) ; Nagano Pref., 26.v.1924, leg. Murata (1 ♂ 1 ♀, TUA); Nagano-ken, Shimotakai, vii.1930, collector unknown (1 ♂ 1 ♀ 1 terminalia missing, ELKU) ; as above but 8.viii.1930 (1 ♂ 2 ♀♀, ELKU, 1 ♂ 3 ♀♀ KUM); Nagano-ken, Okaya-shi, Kohan, near Suwa Lake, 3603'29.0" N 13803 '54.5"E, 12.viii.2018, leg. J. Souma (1 ♂, TUA) .

Diagnosis. Recognized among other species of Physatocheila by a combination of the following characters: general color brown (Figs. 8C, 9C, 10C, 11C); median spine on head extending beyond bases of frontal spines; rostrum reaching posterior margin of abdominal sternite III; pubescence on pronotum less than 0.5 times as long as diameter of compound eye; lateral carinae of pronotum close to each other in anterior part, concealed by paranotum in anterior part; paranota incompletely covering pronotal disc in anterior part, not touching each other, not concealing median carina of pronotum, widened posteriorly, not bulged upward in posterior part, not forming a cyst; outer margin of paranotum gently curved outward in its entire length; costal area of hemelytron wider than subcostal area at widest part, less than 0.5 times as wide as discoidal area at widest part, with 2 rows of areolae in its entire length; and subcostal area subhorizontal, with 3 rows of areolae in its entire length.

Description of genitalia. Pygophore (Figs. 10C, 17E) compressed dorsoventrally, hexagonal in ventral view, strongly concave at anterior margin of dorsum, elevated at center of venter, smooth on surface, irregularly punctate in middle part of dorsum. Paramere (Fig. 18E) expanded in middle part, curved inward in apical part; outer and inner margins covered with pubescence in middle part. Female terminalia (Fig. 11C) pentagonal in ventral view, covered with pubescence.

Remarks. Overall, P. distinguenda closely resembles P. nigrintegerrima but can be distinguished from it by the following characteristics: general color brown (Fig. 8C, 9C, 10C, 11C); a pair of frontal spines on head reaching beyond tip of clypeus; median spine on head extending beyond bases of frontal spines; a pair of occipital spines on head reaching anterior margin of compound eyes; rostrum reaching posterior margin of abdominal sternite III; and costal area wider than subcostal area at widest part.

In Japan, this species is known as a pest of cultivated basket willow (Baba 1925; Murata & Ikeda 1925; Murata 1928; Takeya 1930; Japanese Society of Applied Entomology and Zoology 1980, 2006; Yamada & Tomokuni 2012).

Distribution. Japan (Honshu, Shikoku), China, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Russia.

Host plant. In Japan and Eurasia, this species occurs on the following salicaceous plants: Populus sp. (Kwon et al. 2001); Salix alba L. (Putshkov 1974; Golub 1988b; Kwon et al. 2001); S. bebbiana Sarg. [= S. xerophila Flod.] (Putshkov 1974; Golub 1977a; Golub 1988b; Kwon et al. 2001); S. koriyanagi Kimura ex Goerz [= S. purpurea L.] (Baba 1925; Takeya 1930, 1951; Hasegawa 1960; Golub 1988b; Kwon et al. 2001; Yamada & Tomokuni 2012); S. rosmarinifolia L. (Golub 1977a, 1988b; Kwon et al. 2001); Salix sp. (Golub 1977b; Kwon et al. 2001); and S. sieboldiana Blume (Notsu & Watanabe 2020) .

Biology. In Japan, this species is univoltine and feeds on the branches of cultivated basket willow [= S. koriyanagi]. Overwintering adults are found on the underside of fallen leaves. After hibernation, adults copulate from late May and then oviposit until mid-June. Nymphs hatch from early July and mature by late August (Baba 1925; Murata 1928). Adults are observed in almost all seasons in Japan (Baba 1925; Murata 1928; Takeya 1930; Miyatake 1958; Hasegawa 1960; Tomokuni 1979, 1994; Maehara 2010; Yamada & Tomokuni 2012; Nozaki & Nozaki 2013; Notsu & Watanabe 2020; present study).