Holotype. ♀, Taiwan: Taoyuan, Fuxing, Lalashan, ca. 1500 m, 13 Mar 2018, reared from Microsorum brachylepis, emg. 22 Apr 2018, Y. F. Hsu, C. W. Huang, C. J. Chang Coll. Paratypes. 1♂, Taiwan: New Taipei City, Shuangxi, Yingtzailing, ca 1000 m, 29 Dec 2017, reared from M. brachylepis, emg. 11 Feb 2018, Z. Y. Shen, Y. Y. Lu, C. J. Chang Coll. (NTNU). 2♂, 3♀, same data as holotype, emg. 9–17 Apr 2018, Y. F. Hsu, C. W. Huang, C. J. Chang Coll. (1♂, Gen. Prep. ZYS-0009, NTNU). 4♀, Taiwan:Taoyuan, Fuxing, Lalashan, ca. 1500 m, 16 Mar 2019, reared from M. brachylepis, emg. 19–22 Apr 2019. Z. Y. Shen and G. Y. Chen Coll. (1♀, Gen. Prep. ZYS-0090, NTNU).

This species can be distinguished from congeneric species by the following characters in genitalia: costa considerably thicker than in the others and basal sclerotized structure in aedeagus not developed. This species can be separated from sympatric C. insolita by coloration of abdomen in ventral view: fuscous scales extending ventrad and visible in fourth and fifth abdominal segment in this species, but not extending ventrad and invisible in C. insolita.

Male (Figs 1, 2). Forewing length 3.25–3.94 mm (N = 3). Head: antenna black, white apically, scape ocherous orange; labial palps slender, long, strongly upcurved, ocherous orange; frons grey, sub-shiny; vertex narrow, bronzy-purple; occiput bronzy-purple, sub-shiny. Thorax: surface covered by shiny bronzy-purple scales. Legs: fore and middle legs shiny grey tinged with white, mesotibia bearing a pair of apical spurs, with outer spur less than 1/2 length of inner spur; hind legs silvery, overlaid with dark brown scaling dorsally; tibia bearing prominent, black, proximal hair tuft and a whirl of orange bristles; tarsus with each tarsomere bearing a whirl of dark brown bristles, metatibia bearing two pairs of spurs, proximal spurs with outer one approximately 1/3 length of inner one, apical spurs with outer one approximately 1/2 length of inner one. Forewing: upperside ground color shiny bronzy-purple with dark brown patch at the 1/3 of costal margin of wing, cilia fuscous; underside uniformly fuscous. Hindwing: ground color uniformly pale fuscous on both sides, cilia fuscous. Abdomen: shiny bronzy-purple dorsally; whitish grey with fuscous lateral markings visible in fourth and fifth abdominal segment from ventral view; anal tuft present.

Female (Figs 3, 4). Forewing length 4.03–4.23 mm (N = 5); Similar to male but lacking anal tuft in abdomen.

Male genitalia (Gen. Prep. ZYS-0009, NTNU, Figs 9, 10). Uncus acute-triangular, down-curved apically, with apex truncate; gnathos acute-triangular, slightly longer than uncus, with acute apex; tegument well developed; valva rounded posteriorly; costa thicker than sacculus; costa obvious oblique ventrally; cucullus oval, as long as uncus, with numerous setae on inner surface; saccus approximately 1/2 length of uncus; aedeagus stout, approximately 3× as long as uncus, basal sclerotized structure not development.

Female genitalia (Gen. Prep. ZYS-0090, NTNU, Fig. 13). Apophyses anteriores nearly as long as apophyses posteriores; ostium bursae with prominent sublateral fold, with numerous small spines on inner surface; corpus bursae with large signum, bar-shaped, situated at the middle of corpus bursae, small spines present near the connection of corpus bursae and bulla; bulla assimilated with ductus seminalis; many small spines present at proximal end of ductus seminalis.

The specific name is derived from the name Atayal, referring to the indigenous people who live in the region of the type locality.

Microsorum brachylepis (Baker) T. Nakaike, 1981 (Polypodiaceae)

Larva (Fig. 16) vermiform, slender, slightly tapering toward the caudal end; body is creamy white in color, with head capsule and prothoracic shield dark brown, glossy. Pupa (Fig. 17) oval in shape, with head obtuse, attenuate to pointed caudal end.

Larvae were found in January and May. They construct tunnel-like shelters on the underside of the host plant leaves (Fig. 15), composed of fern spores and its own frass. The larvae (Fig. 16) live inside the shelter and feed on the spores until pupation. The pupae (Fig. 17) construct loose cocoons within larval shelters. Adult moths emerged nearly one month after pupation without diapause, suggesting that this species may be multivoltine.

Known only from Taiwan.

Holotype. ♀, Taiwan: New Taipei City, Xindian, Hemeishan, ca. 150 m, 29 Apr 2018, reared from Tectaria harlandii, emg. 20 May 2018, Z. Y. Shen Coll. Paratypes. 1♂, 2♀, same data as holotype, emg. 17 May 2018, Z. Y. Shen Coll. (1♂, Gen. Prep. ZYS-0026, NTNU. 1♀, Gen. Prep. ZYS-0091, NTNU). 1♂, 1♀, Taiwan: Taina, Dongshan, Kantoushan, ca. 600 m, 18 Sep 2018, reared from Tectaria subtriphylla, emg. 5–6 Oct 2018, Y. F. Hsu Coll. (NTNU).

This species may be distinguished from other congeneric species by the presence of peculiar specialized clavate setae at the base of the cucullus. The ventral side of the abdomen has the same color pattern as C. atayalica, but they can be distinguished by the visibility of fuscous scales in fourth and fifth abdominal segment.

Male (Figs 5, 6). Forewing length 3.07–3.47 mm (N = 2). Head: antenna black, white apically, scape ocherous orange; Labial palps slender, long, strongly upcurved, ocherous orange; proboscis covered by maxillary palps; frons grey, sub-shining; vertex narrow, bronzy-purple, sub-shining; occiput bronzy-purple, sub-shining. Thorax: surface covered with shiny bronzy-purple scales.; Legs: fore and middle legs creamy orange, with dark brown patches in mesotibia, mesotibia bearing a pair of apical spurs, with outer spur less than 1/2 length of inner spur; hind legs creamy orange with dark brown patches in metatibia, extensive dark brown scaling on tarsus; tibia bearing prominent black, proximal hair tuft and a whirl of orange bristles; tarsus with each tarsomere bearing a whirl of dark brown bristles, metatibia bearing two pairs of spurs, proximal spurs with outer one approximately 1/3 length of inner one, apical spurs with outer one approximately 1/2 length of inner one. Forewing: upperside ground color shiny bronzy-purple with dark brown patch at 1/3 of costal margin of wing, cilia fuscous; underside uniformly fuscous. Hindwing: ground color uniformly pale fuscous on both sides, cilia fuscous. Abdomen: shiny bronzy-purple dorsally; grey tinged with white, without fuscous lateral markings visible in fourth and fifth abdominal segment from ventral view; an anal tuft present.

Female (Figs 7–8). Forewing length 2.04–3.64 mm (N = 4). Similar to male but lacking anal tuft in abdomen.

Male genitalia (Gen. Prep. ZYS-0026, NTNU, Figs 11, 12). Uncus slightly curved apically, with sharp apex, numerous setae present laterally; gnathos narrow, slightly longer than uncus, with truncate apex; tegument well developed; valva rounded posteriorly; sacculus slightly thicker than costa; cucullus oval, longer than uncus with numerous setae on inner surface, a few specialized clavate setae present on cucullus basally; saccus approximately 1/3 length of uncus; aedeagus stout, approximately 1.5× as long as uncus, basal sclerotized structure hook-shaped.

Female genitalia (Gen. Prep. ZYS-0091, NTNU, Fig. 14). Apophyses posteriores longer than apophyses anteriores; ostium bursae with prominent sublateral fold with numerous small spines on inner surface; corpus bursae small with prominent signum, bar-shaped, situated at the middle of corpus bursae; small spines present at the basal of bulla; bulla assimilated with ductus seminalis; many small spines at proximal end of ductus seminalis.

The species name is the feminine form of the Latin adjective insolitus, for uncommon or unusual, referring to the peculiar clavate setae on the inner surface of the valva not found in any other known stathmopodid moth.

Tectaria subtriphylla (Hook. & Arn.) Copel., 1907 and T. harlandii (Hook.) C. M. Kuo, 2002 (both Tectariaceae).

Larva (Fig. 19) vermiform, elongate, somewhat stout, abruptly tapering toward the caudal end; body is creamy white in color, with head capsule and prothoracic shield pale brown, glossy. Pupa (Fig. 20) oval in shape, with head obtuse, attenuate to pointed caudal end.

Larvae were found in March and September. Larvae associated with T. harlandii construct tunnel-liked shelters (Fig. 18) and live gregariously on the underside of the sporophyll. Larvae (Fig. 19) associated with T. subtriphylla produce tunnel-liked shelters individually, and also live on the underside of leaves. The pupae (Fig. 20) construct loose cocoons within larval shelters. Larvae were found in spring and autumn; adult moths emerged about one month after pupation, suggesting that the species is multivoltine.

Known only from Taiwan.