Siobla apicalis Takeuchi 1929

Siobla apicalis Takeuchi, 1929

(Figs 1 a–b, 5a–b, 6a, 7a, 8a, j)

Siobla pacifica: Takeuchi, 1919a: 184; Takeuchi, 1919b: 14. Not Smith (1874).

Siobla apicalis Takeuchi, 1929: 496; Malaise, 1934: 25; Takeuchi, 1937: 57.

Siobla venusta apicalis: Malaise, 1945: 127; Takeuchi, 1950: 1348; Takeuchi, 1952: 18; Togashi, 1955: 25; Togashi, 1961: 32; Togashi, 1965: 246, plate 123, 29; Togashi, 1970b: 18; Okutani, 1974b: 195; Kim, 1980: 37; Naito, 1982: 574; Otsuka, 1984: 12; Nambu, 1992: 11; Nambu, 1998: 22; Lee et al., 2000: 119; Togashi & Yamamoto, 2000: 716; Katayama, 2004: 96; Naito et al., 2004: 57; Yoshida, 2006: 91; Togashi, 2008: 490, plate 142, 2537; Lee et al., 2010: 165; Taeger et al., 2010: 585; Niu & Wei, 2010: 50.

Siobla venusta: Okutani, 1973: 19. Not Konow (1903).

Distribution. Japan (Honshu, Shikoku, Kyushu [new record]); Korea.

Primary type examined. Holotype of Siobla apicalis: ♀, “ 26. VII. 1929, Kose, near Karuizawa, Takeuchi” “ Siobla apicalis Takeuchi, Holotype ” (OPU).

Other material examined (see Appendix). 120 specimens (49♀ and 71♂).

Variation. The length varies from 12.5 to 16.0 mm in the female and 10.0 to 14.0 mm in the male. The colouration varies little except for the extent of pale areas on the abdomen. The abdominal tergum 2 in the female is whitish with a black area dorsally; the black area covers the whole dorsal surface in very dark specimens, while it becomes a median longitudinal stripe in very pale specimens. The male has the abdominal terga 2 to 4 reddish brown usually with a black spot on the anteromedian margin of the tergum 2, and the lateral sides of the terga 3 and 4 and the posterior margin of the tergum 4 are often marked with black. In one exceptionally dark male specimen, the hind leg is mostly blackish, with only a narrow whitish ring on the tibia and a pale brownish base of each tarsomere, and the abdomen is black except for the pale brown lateral sides of the tergum 2 and the pale brown anterior margins of the terga 3 and 4. The ranges of some ratio variations are given in the key.

Remarks. This species belongs to the S. venusta group (Niu & Wei 2010). It is separated from the congeners in Japan by the colour of the antenna, shape of the head, and colour of the female abdomen (see the key above for details). Malaise (1945) treated this species as a subspecies of S. venusta (Konow, 1903) from China and Russia and subsequent authors followed him. We treat S. apicalis as a full species distinct from S. venusta because S. apicalis differs from S. venusta in having all the trochanters and trochantelli black, the hairs on the head and thorax silver, the upper margin of the metepisternum densely and clearly punctured, and the outer surface of the hind coxa densely punctured. In the latter species, most of the fore and middle trochanters and trochantelli are pale with small dark spots, the hind trochanter and trochantellus are pale, hairs on the head and thorax are pale brown, the upper margin of the metepisternum is sparsely and indistinctly punctured and the outer surface of the hind coxa is sparsely punctured.