Review of the genus Periacma Meyrick (Lepidoptera, Oecophoridae) from China, with descriptions of four new species

The species of Periacma Meyrick from China are reviewed. Thirty‐two species are treated, including four new species (P. latizona sp. nov., P. leyensis sp. nov., P. spinivalvula sp. nov. and P. rectignatha sp. nov.). Females of four species (P. iodesma vietnamica Lvovsky, P. zhouzhiensis Wang & Zheng, P. binchuanensis Wang & Zheng and P. equivalvata Wang, Li & Liu) are described for the first time. Periacma chengchengensis Wang & Zheng is synonymized with P. delegate Meyrick, and Periacma plumbea Meyrick is newly recorded from China. Photographs of the adults treated here and the genital structures of the new species are provided. A distribution map of Periacma Meyrick in China and a key to all the Chinese species, except P. isanensis Moriuti et al., are given based on the male genitalia.


Introduction
Periacma Meyrick was proposed in 1894 with P. ferialis Meyrick as its type species. It is characterized by having two-segmented labial palpus in the male, a dorso-proximal process of the valva in the male genitalia and developed apophysis anterioris in the female genitalia. Species of the genus are somewhat difficult to distinguish superficially; fore wing ground colour ranges from light yellow to ocherous yellow, with brown or dark brown fascia or marks. However, members of the genus can be easily differentiated by both male and female genital structures.

Periacma ferialis
Distribution: China (Anhui, Hunan, Jiangsu, Shanghai, Sichuan), India, Vietnam. Remarks: Periacma iodesma is closely allied to P. orthiodes Meyrick both superficially and in genitalia. It can be differentiated from the latter by the uncus with the caudal margin nearly straight, the gnathos with the anterior margin bluntly rounded, and the aedeagus with more than two tooth-like spines in the male genitalia.
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. Moriuti, Saito & Lewvanich, 1985 ( Figure 5) Periacma siamensis Moriuti, Saito & Lewvanich, 1985: 25;Wang and Li, 2002: 570. Wing expanse: 13.0-15.0 mm. Remarks: This species resembles P. orthiodes, but can be distinguished from the latter by the male genitalia with the gnathos slightly concave at middle of the anterior margin and the sacculus apically rounded. Distribution: China (Guangxi, Yunnan), Vietnam. Remarks: The slight differences between Periacma iodesma vietnamica Meyrick and P. iodesma Meyrick lie in: uncus rounded caudally, gnathos roundly protruded forward and aedeagus with more tooth-like spines throughout in the former subspecies; while uncus straight caudally, gnathos bluntly rounded anteriorly and aedeagus with fewer tooth-like spines in the nominate subspecies.

Periacma siamensis
The female of this species is described for the first time. Remarks: This species is characterized by the gnathos with the ventral plate somewhat axe-like, the sacculus roundly projected near distal end, and the aedeagus with a narrow band at middle in the male genitalia; and the corpus bursae without signum but with two slightly sclerotized areas in the female genitalia.
Remarks: This species is distinguished by the gnathos more or less T-shaped, the valva with distal two-thirds nearly parallel-sided and the dorso-proximal process distally bulbous in the male genitalia.
The female of this species is described for the first time.
Remarks: This species is characterized by the sacculus not curved. It is related to P. orthiodes, but can be distinguished by the gnathos apically blunt and the sacculus much longer in the male genitalia; and the signum absent in the female genitalia.  Fengxian (33u559N, 106u319E), Shaanxi Province, 1600 m, 13 July 1988, coll. Houhun Li. Paratypes: 1 ", 2 RR, 16-20 July 1987, other same data as holotype; 1 ", 14 July 1988, same locality data as allotype.
Distribution: China (Shaanxi). Remarks: This species is characterized by the gnathos with the ventral margin straight and the aedeagus with the distal portion dentate at both sides in the male genitalia; and the corpus bursae with two differently shaped signa in the female genitalia.   Remarks: This species can be easily separated from other species of the genus by the digitate process at basal 1/5 of the costa of the valva.
The female genitalia of this species are described for the first time.
Distribution: China (Yunnan). Remarks: This species resembles P. fengxianensis, but can be distinguished from the latter by the uncus not dilated apically, the sacculus heavily sclerotized distally, and the aedeagus with distal 1/6 divided into two parts.
Distribution: China (Yunnan) Remarks: This species is similar to P. ziyangensis and P. changkhianensis. It can be separated from P. ziyangensis by the sacculus with a sclerotized plate at middle of the ventral margin and a small process near distal process in the male genitalia; and the signum present in the female genitalia. It can be distinguished from P. changkhianensis by the female lamella postvaginalis with the posterior margin not concave at middle but blunt, and the anterior margin heavily sclerotized. Remarks: This species is characterized by the uncus distally rhomboid and the sacculus apically truncate in the male genitalia; and the lamella antevaginalis laterally forming two large plates in the female genitalia. Remarks: This species is distinguished by the uncus with a pointed process at the apex, the valva gradually narrowed from the base to the apex, and the sacculus without a distinct distal process. Remarks: This species can be separated from other members of the genus by the gnathos nearly annular, the valva nearly parallel-sided from the base to the apex, and the aedeagus with distal portion produced into two large, densely spined processes.
The female genitalia of this species are described for the first time.  Redescription: Wing expanse 11.0-12.0 mm. Head ochreous yellow. Labial palpus ochreous yellow except second segment whitish on dorsal surface. Antenna pale orange yellow on ventral surface, brown on dorsal surface. Thorax and tegula ochreous yellow mixed with ochreous brown. Fore wing ochreous yellow, with ochreous brown scales throughout, somewhat erect and denser in distal third; with three distinct tufts of dark brown scales: one at middle of cell, other two placed one above another near end of cell; costa with a triangular dark brown spot just beyond middle; dorsum with a dark brown spot at base; elongate streak from near base extending along fold; cilia ochreous yellow tinged with grayish brown. Hind wing and cilia deep gray. Fore and mid legs ochreous brown, with dark brown spots; hind leg grayish yellow, with dark brown spots on tarsi.
Male genitalia ( Figure 33): Uncus elongate, somewhat narrowly contracted medially, rounded at apex. Gnathos longer than uncus, curved, heavily sclerotized, pointed apically. Valva narrow, nearly same width from base to apex, rounded at apex, with a row of large setae from near base and costa obliquely extending to 2/5 of dorsum; costa concave, with an elongate projection beyond middle; dorso-proximal process with long hairs distally. Sacculus somewhat broad triangular, about half as long as costa, apically produced to a hooked process directing upward. Saccus triangular. Aedeagus strong, divided into two branches from middle: ventral one strong and curved downward; dorsal one thin, slightly arched, pointed distally.
Remarks: This species is closely related to P. erawanensis, but can be distinguished by the somewhat finger-like gnathos, the valva not expanded distally, and the aedeagus divided into two distal processes. In the latter species, the gnathos is triangularly shaped, the valva is medially expanded and the aedeagus bears three distal processes.
This species is reported from China for the first time. Paratype: 1 R, same data as holotype.

Description of new species
Description: Wing expanse 11.0-12.0 mm. Head whitish yellow. Labial palpus mostly ocherous in male, whitish yellow in female; male second segment dorsally with dark brown scales, forming a somewhat longitudinal dark line in distal 3/5; female second segment with dark brown scales near end, forming a dark ring, third segment about 3/5 as long as second, long and thin, pointed apically. Antenna mostly brown. Thorax, tegula, and fore wing light yellow, with scattered brown scales throughout. Fore wing lanceolate ( Figure 29); apex rounded; termen gently oblique; dark brown blotch extending from base of posterior margin obliquely upward to base of cell at middle, forming a somewhat arched band; brown spot at middle of cell and at 3/5 of fold; brown fascia from distal 1/3 of costa extending outward to before tornus; apex with large brown patch; cilia whitish yellow, gray around tornus. Hind wing and cilia gray. Legs light grayish white, tibiae and tarsi with brown speckles; spurs light ocherous yellow.
Remarks: This species is closely related to Periacma maekhongensis, but can be distinguished by the lamella postvaginalis anteriorly possessing two sclerotized leaf-like processes extending downward from the anterior angles in the female genitalia.
Etymology: The specific name is from the type locality, Leye, Guangxi Zhuangzu Autonomous Region. Description: Wing expanse: 17.0-20.0 mm. Head orange yellow, somewhat ocherous, tinged with black scales laterally. Labial palpus orange yellow; in male basal segment with black scales on outside, second segment with black scales on ventral surface near apex, apex pointed; in female basal and second segments thick, with scattered black scales on outside, third segment much thinner, about 2/3 length of second, point apically. Antenna yellowish brown, with deep brownish rings. Thorax, tegula and fore wing orange yellow, somewhat ocherous; thorax posteriorly with a grayish black spot, tegula with grayish black spot at base. Fore wing broad (Figure 30), suffused with grayish black scales; costal margin gently arched, with an elongate grayish black blotch at base; ventral margin with a large blackish blotch at base, more or less diffused upward and exceeding fold to near middle of cell; dim dot set at middle of cell near upper margin; broad grayish fascia extending from costal 3/5 to 2/3 of dorsum, widest at costal margin, gradually narrowed to middle, then widened again at dorsum; large grayish fascia extending from apex along termen to before tornus, where joined with the first fascia, forming a ''V'' with pointed apex; termen oblique; cilia grayish yellow, tinged with grayish black. Hind wing and cilia deep gray. Fore leg with femur whitish gray, with black scales, tibia and tarsus orange yellow, with black patches or spots; mid leg with femur whitish yellow, tibia and tarsus black, with whitish yellow spots; hind leg whitish yellow, tarsus with gray spots. Abdomen brown on dorsal surface, apical portion and ventral surface whitish yellow. Abdomen brown, yellow in distal portion.
Remarks: This species is similar to Periacma wongsirii, but can be separated from it by the following characters: two fore wing fasciae joined at tornus forming a distinct ''V''; gnathos anteriorly spined, sacculus without distinct process, and aedeagus with a large distal spine.
Etymology: The specific name is derived from the Latin latizonus, in reference to the wide fascia of the fore wing. Paratypes: 3 "", 5 RR, 10-14 August 2003, same locality data as holotype. Description: Wing expanse: 9.0-11.0 mm. Head whitish yellow. Labial palpus light yellow; in both male and female second segment with a black ring near end; in female third segment thin and pointed. Antenna yellow; scape black on dorsal surface; flagellum ringed with brown. Thorax, tegula, and fore wing light yellow, with scattered brown scales. Fore wing lanceolate ( Figure 31); costal margin gently arched; apex roundly pointed; termen oblique; dark brown blotch from base of posterior margin extending to 1/3 of fore wing at middle; brown fascia from about costal 2/3 to before tornus, broader in anterior and posterior portion, median portion narrow; cilia light yellow except brown on tornus. Hind wing and cilia gray. Legs whitish yellow, tinged with brown on tibiae and tarsi.
Male genitalia (Figure 36): Uncus short, somewhat trapezoidal, laterally with long setae in basal 2/3; caudal margin almost straight. Gnathos with lateral arms and ventral plate short; ventral plate with straight anterior margin. Tegumen large and broad. Valva narrow, nearly parallel-sided from base to distal 2/3, then gradually narrowed to apex; apex with a spine; dorso-proximal process slender, stick-like. Sacculus broad, less than half of valva, with pointed apex. Vinculum narrow. Saccus short, more or less triangular. Aedeagus stout, distally with four apically blunt processes.
Remarks: This species can be distinguished from its congener by the dorsal spine at the apex of the valva, the dorsally pointed process at the apex of the sacculus, and the four short processes at the distal end of the aedeagus.
Etymology: The specific name is from the Latin prefix spin-(spine) and valvulus (valva), in reference to valva with a spine at apex. Description: Male wing expanse: 10.0 mm. Head light yellow. Labial palpus light yellow, second segment with a black ring near end; in female third segment thin and pointed. Antenna yellow; flagellum yellow and brown. Thorax, tegula, and fore wing light yellow, with scattered dark brown scales; tegula with black spot at base. Fore wing lanceolate ( Figure 32); costal margin gently arched, with a dark brown patch at base; apex rounded; brown dot at middle and end of cell, and at 2/3 of fold; brown fascia extending from costal 2/3 to tornus; cilia light yellow, mixed with brown at tornus. Hind wing and cilia light gray. Legs whitish, with brown speckles on outside of tibiae and tarsi.
Remarks: This species resembles Periacma spinivalvula sp. nov., but can be separated by the fore wing with three brown dots, the valva without spine at apex, and the aedeagus with only one pointed process distally.
Etymology: The specific name is from the Latin rect-(straight) and gnathus (gnathos), in reference to the straight anterior margin of the gnathos.