Periacma Meyrick, 1894

Wang, S. X. & Li, H. H., 2006, Review of the genus Periacma Meyrick (Lepidoptera, Oecophoridae) from China, with descriptions of four new species, Journal of Natural History 40 (41 - 43), pp. 2371-2393 : 2373

Genus Periacma Meyrick, 1894

Periacma Meyrick, 1894: 21 ; Gaede, 1939: 380; Clarke, 1963: 349; Moriuti et al. 1985: 21. Type species: Periacma ferialis Meyrick, 1894 , by original designation.

Diagnosis: Head with loosely appressed scales. Labial palpus recurved, thickened with appressed scales, two-segmented in male; three-segmented in female, with third segment thinner and shorter than second. Antenna filiform, about 4/5 length of fore wing; without pecten. Fore wing broad, with brown or dark brown fascia in most species; twelve veins present: R 1 arising from before middle, R 4 and R 5 stalked, R 5 reaching costa or apex; M 3 nearer to M 2 than to CuA 1; CuA 1 arising from angle, CuA 2 from before angle, CuP absent. Hind wing elongate-ovate; M 3 and CuA 1 connate from angle. Abdomen with tergites spined.

Male genitalia: Uncus large and usually dilated distally. Gnathos with mesal spatulate plate. Valva with a dorso-proximal process at base of costa. Sacculus developed. Aedeagus short, varied in shape; cornutus present or absent.

Female genitalia: Apophysis posterioris longer than apophysis anterioris. Signum present or absent.

Remarks: Periacma Meyrick is closely related to Ripeacma Moriuti et al. and Irepacma Moriuti et al. It can be separated from Ripeacma by the absence of the transtilla and the presence of a dorso-proximal process of the valva in the male genitalia; in Ripeacma , the transtilla is well developed and the valva lacks dorso-proximal process. It can be distinguished from Irepacma by the dorso-proximal process of the valva being shorter than half the length of the valva in the male genitalia and by the apophysis anterioris developed in the female genitalia. In Irepacma , the dorso-proximal process usually far exceeds half of the valva length, if present, and the apophysis anterioris is completely absent.