Pachyrhabda citrinacma Meyrick, 1936

Shen, Zong-Yu, Su, Hung-En & Hsu, Yu-Feng, 2024, Rediscovery of the mysterious Taiwanese micromoth Pachyrhabda citrinacma Meyrick, 1936 (Stathmopodidae) in museum and field, with notes on the fern-spore feeding larva, Zootaxa 5446 (2), pp. 288-294 : 289-292

Pachyrhabda citrinacma Meyrick, 1936

Figure 1–3

Pachyrhabda citrinacma Meyrick, 1936: 617 . Type locality: “Taihoku, Formosa ”.

Material examined

Syuti Issiki-collected specimen: The specimen of Pachyrhabda citrinacma retrieved in ( NTUE). 1 ♂, Taiwan: “ ♂. Taiwan, Sinten [=Xindian], 17 Apr 1935, S. Issiki Coll. (1♂, Gen. Prep. ZYS-0252, NTUE). ( Fig. 1 ; Fig. 3A–B ) .

Additional material examined. 3♀, Taiwan: New Taipei City, Xindian, Sikanshui , ca 500m, 12 Feb 2018, reared from Asplenium nidus , emg. 24 Mar–1 Apr 2018, Z. Y. Shen Coll. ( NTNU) . 1♂, 1♀, Taiwan: Yilan, Datong, Qilanshan , ca. 420m, 25 Mar 2018, reared from Aglaomorpha coronans , emg. 15 Apr–1 May 2018, Z. Y. Shen Coll. ( NMNS) . 1♀, Taiwan: Tainan, Dongshan, Kantoushan , ca. 600 m, 4 Jul 2018, reared from Asplenium nidus , emg. 29 Jul 2018, Y. F. Hsu Coll. ( NTNU) . 1♂, Taiwan: Taizhong, Heping, Shaolai , ca. 800m, 30 Sep 2018, reared from Neolepisorus fortunei , emg. 1 Oct 2018, Y. Y. Lu Coll. ( NMNS) . 3♂, 2♀, Taiwan: New Taipei City, Wulai, Fushan, ca. 800m, 7 Jan 2019, reared from Antrophyum formosanum , emg. 10–23 Feb 2019, Y. F. Hsu Coll. (1♂, Gen. Prep. ZYS-0083, NTNU) . 1♂, 13♀, Taiwan: New Taipei City, Wulai, Fushan, ca. 800m, 11 Feb 2020, reared from Antrophyum formosanum , emg. 11–28 Mar 2020, Y. F. Hsu Coll. (1♀, Gen. Prep. ZYS-0204, NTNU) . 2♂, 1♀, Taiwan: Kaohsiung, Taoyuan, Fenggangshan , ca 1000m, 20 May 2020, reared from Asplenium antiquum ,emg. 27 Jul–19 Aug 2020, Z. Y. Shen, J. Y. Liang Coll. ( NTNU) .

Redescription. Male ( Fig. 2A–B ): Forewing length 2.7–3.5 mm (n=3). Head: frons white, vertex covered by whitish-ocherous scales, occiput ocher; antenna with scape rod-shaped, white with black scales at the connection of flagellum, flagellum white; labial palps slender, long, strongly upcurved, white. Thorax: ocher with whitish streak on the anterior and posterior margin respectively. Legs: white; ventral side of fore legs covered by scales; mesotibia bearing a pair of spurs at distal joint, with outer spur approximately 1/2 length of inner spur; hind legs with black scales overlaid at junction of tibia and tarsus; metatibia overlaid with whitish bristles; metatibia bearing two pairs of whitish spurs at both proximal and distal joints, proximal spurs with outer one approximately 1/3 length of inner one, distal spurs with outer one approximately same length as inner one; metatarsus bearing a whorl of whitish bristles on each tarsomere. Forewing: ground color white with two ocherous blotches, widest toward costa, one located at -base and the other at middle of wing; cilia white. Hindwing: ground color white; cilia white. Abdomen bright orange-ocher; anal tuft present.

Female ( Fig. 2C–D ): Forewing length 3.3–3.4 mm (n=3). Similar to male but lacking anal tuft in abdomen.

Male genitalia ( Fig. 3C–D ): Uncus elongated triangular, apically down-curved, with acute apex, setae present laterally; gnathos tongue-shaped, approximately same length as uncus; tegumen well-developed; valva nearly oblong; costa acute at base; sacculus acute at base; costa nearly as thick as sacculus; cucullus oval, nearly same length as uncus, with numerous setae on inner surface; saccus nearly the same length as uncus; anellar lobes oval with numerous setae; phallus stout, approximately 3x as long as uncus, basal sclerotized structure developed, acute triangular, cornutus absent.

Female genitalia ( Fig. 3E ): Papillae anales longer than width; apophyses posteriores slightly longer than apophyses anteriores; ostium bursae funnel-shaped; ductus bursae shorter than corpus bursae, corpus bursae with horn-shaped signum, situated at about anterior 1/3 of corpus bursae; bulla round; ductus seminalis with many small spines present at proximal end.

Diagnosis. This species is superficially similar to Pachyrhabda antinoma Meyrick, 1910 and P. inanis Meyrick, 1936 . However, it can be distinguished from these two species by the distinctive color of its thorax. While the thorax of P. citrinacma exhibits an ocherous coloration, the thorax of P. antinoma and P. inanis is characterized by a whitish coloration.

Host plants. Asplenium antiquum Makino, 1929 , A. nidus L., 1753 ( Aspleniaceae ), Aglaomorpha coronans (Wall. Ex Mett.) Coppel., 1929 , Neolepisorus fortunei (T. Moore) L. Wang ( Polypodiaceae ), and Antrophyum formosana Heron., 1915 ( Pteridaceae ).

Biology. Larvae have been collected nearly the whole year in Taiwan. They constructed roughly oval shelters on the underside of the host fern fronds, adorned with silk, fern spores and their own frass ( Fig. 4A ). The larva ( Fig. 4B ) lived inside the shelter and fed on the spores until pupation. The pupae, which were oval-shaped, were enclosed within loose cocoons situated within the larval shelters ( Fig. 4C ). About one to one and a half month after pupation, adult moths ( Fig. 4D ) emerged without undergoing diapause.

Distribution. Taiwan.

Figures

FIGURE 1. Issiki collected specimen of Pachyrhabda citrinacma Meyrick, 1936. Specimen of Pachyrhabda citrinacma from NTUE, TAIWAN: New Taipei City, Xindian. Scale bar = 1 mm.

FIGURE 2. Adults of Pachyrhabda citrinacma Meyrick, 1936. A, B: Male specimen, TAIWAN: Kaohsiung, Taoyuan, Fenggangshan. C, D: Female specimen, TAIWAN: Kaohsiung, Taoyuan, Fenggangshan. Scale bars: A, B, C, D = 5 mm.

FIGURE 3. Genitalia of Pachyrhabda citrinacma Meyrick, 1936.A, B: Male genitalia of Issiki-collected specimen. C, D: Male genitalia, TAIWAN: New Taipei City, Wulai, Fushan (Gen. Prep. ZYS-0083, NTNU). E: Female genitalia, TAIWAN: New Taipei City, Wulai, Fushan (Gen. Prep. ZYS-0204, NTNU). Scale bars: A, B, C, D, E = 0.5 mm.

FIGURE 4. Immatures and adults of Pachyrhabda citrinacma. A: Immature artifacts on Asplenium antiquum. B: Larva and its artifacts on Antrophyum formosana. C: Pupa on A. formosana. D: Adult and its resting posture.