(Figure 4)
Periacma delegata Meyrick, 1914: 52; Gaede, 1939: 194; Moriuti, 1982: 205.
Periacma chengchengensis Wang & Zheng, 1995: 5. syn. nov.
Wing expanse: 12.0–14.0 mm.
Material examined: 3 „„, 2 ♀♀, Neixiang (33 ° 02 9 N, 111 ° 50 9 E), Henan Province, 650 m, 12 July 1998, coll. Houhun Li; 32 „„, 12 ♀♀, Huixian (35.27 ° N, 113.47 ° E), Henan Province, 780 m, 12–15 July 2002, coll. Xinpu Wang; 3 „„, 4 ♀♀, Huangpu (30 ° 32 9 N, 116 ° 50 9 E), Anhui Province, 24 June 1965; 2 „„, Xuancheng (30 ° 57 9 N, 118 ° 44 9 E), Anhui Province, 10 June 1979, coll. Ju Huang; 4 „„, Badaling (40 ° 22 9 N, 116 ° 01 9 E), Beijing, 700 m, 13 July 1972; 2 „„, Sanbao (40 ° 19 9 N, 116 ° 02 9 E), Beijing, 13 July 1972, other data unknown; 11 „„, 2 ♀♀, Jixian (40 ° 02 9 N, 117 ° 24 9 E), Tianjin, 170 m, 20 July 2004, coll. Houhun Li et al.; 2 „„, Mt. Maoer (45 ° 16 9 N, 127 ° 30 9 E), Heilongjiang Province, 19 August 1964; 100 „„, 32 ♀♀, Jingxing (38 ° 02 9 N, 114 ° 08 9 E), Hebei Province, 1200 m, 23–24 July 2000, coll. Haili Yu et al.; 1 „, Mt. Tai (36 ° 22 9 N, 117 ° 05 9 E), Shandong Province, 12 July 1988; 1 „, 10 August 1993, 1 „, 20 July 1996; 1 „, 7 July 1987, Chengcheng (35 ° 11 9 N, 109 ° 56 9 E), Shaanxi Province, 1000 m, coll. Houhun Li; 2 ♀♀, 26 June 1993, Yangling (34 ° 17 9 N, 108 ° 04 9 E), Shaanxi Province, 450 m, coll. Houhun Li.
Distribution: China (Anhui, Beijing, Hebei, Henan, Heilongjiang, Shaanxi, Shangdong, Taiwan, Tianjin), Japan, Korea.
Remarks: The male genitalia of this species are distinguished by the gnathos somewhat large subtrapezoidal, and blunt apically, and the aedeagus simple, without any ornamentation. The female genitalia are distinguished by the ductus bursae extremely long and not distinctly separated from corpus bursae. Species P. chengchenngensis Wang & Zheng, collected from Shaanxi Province, varies only slightly from this species by sacculus a little longer and with a process somewhat pointed at apex dorsally. We here synonymize P. chengchenngensis Wang & Zheng on the basis of a careful examination of many specimens.