Eastern Asia moth (Dryadaula orientalis) from Japan is very similar to Dryadaula epischista Meyrick 1936

NEWS - Dryadaulidae is assigned to two genera, Dryadaula and Brachydoxa, based on molecular phylogenetic analysis, although both genera were formerly included in Tineidae. Three genera, Eschatotypa, Eugennaea and Sagephora, have been suggested to be included in Dryadaulidae based on asymmetrical male genitalia.

Dryadaula currently has 50 described species and has a pan-global distribution, 14 species in the Palearctic, 16 in the Neotropics, 1 in the Nearctic, 2 in the Afrotropics, 4 in Indomalaya, 12 in Australia, and 2 in Oceania, while Dryadaula pactorlia Meyrick 1901 has been recorded from New Zealand and Europe. Only 2 species are from Japan: D. epischista (Meyrick, 1936) and D. trapezoides (Meyrick, 1935).

The researchers conducted a field survey at the type site to determine the true genital morphology of D. epischista. During the study, they observed that "D. epischista" from Hong Kong did not represent true D. epischista and discovered another unknown species from Japan.

D. orientalis male has a forewing length of 3.0 mm, antenna length of 2.4 mm in holotype. Forewing length of 2.7–3.7 mm (N = 11); antenna length of 1.9–2.6 mm in paratypes (N = 9). Similar to D. epischista except forewing ground color varies from bright orange to dull brown.

Male genitalia, asymmetrical. Uncus elongated and weakly curved to tip, and weakly twisted at middle. Tegumen twisted to the left and slightly wider in the center, fused with vinculum. Vinculum narrowly arched; saccus equipped with an obtuse triangular lobe at middle. Gnathos absent.

Right and left valva clearly asymmetrical. Right valva flat; basal half with broad triangular lobe, protrusions varied from sharp to rounded; apical half densely covered with relatively long setae; basally with small setose curved rod-shaped projection. Left valve thick, but slimmer than right valve, tip paddle-like shaped, with lobate process; lobate process near apical part bearing spinose setae on dorsal surface.

Sternite VIII hollow and curved claw-like shaped; apical spine short and thick; ventral margin with two slender projections, basal projection longer than central projection. Juxta rounded triangle and connected to left valva and phallus.

Phallus asymmetrical elliptical with a curved, thick, and sharp spine apically; and with basal side of projection with or without a straight or curved thin projection; rounded projection attached to juxta; cornuti absent. Intersegmental membrane between seventh and eighth tergite with a pair of free sclerites laterally; right free sclerite broad U-shaped; left free sclerite V-shaped.

Females have a forewing length of 3.0–3.6 mm in paratypes (N = 7), Antenna length 2.2–2.3 mm in paratypes (N = 4). Almost all the same as male, but white spot of subapical part of costal margin narrowed and connected to white line of costal margin in female.

Female genitalia, sternite VIII covered with bristles, strongly sclerotized, right side markedly swollen posterolaterally; terminal swelling passing the ventral edge; ostium bursae opening the posterior end of swelling. Right side of “seventh segment” slightly bulged. Right side of “sixth segment” with posteriorly protruded bulge.

Median dent spherically and strongly concaves between right side of sixth and seventh segments. The analytical papillae are slim and short, the same length as the apophyses posterioris. Apophysis posterioris relatively short, slightly longer than eighth abdominal segment.

Ductus bursae and corpus bursae membranous. Ductus bursae thin tubular, 4× as long as apophysis posterioris. Corpus bursae elliptical, densely wrinkled from ductus bursae side to the end.

Coloration is similar to D. epischista, but the new species can be distinguished by characteristics of male and female genitalia. Male genitalia lack spines on left valve (vs. present in D. epischista); female genitalia have lateral abdominal swellings reaching the end of the abdomen on the eighth segment (vs. not reaching the end of the abdomen in D. epischista).

Adults were observed between May and September. Females lay flat eggs on dead leaves of monocotyledonous plants (Sasa sp.). The name of the new species is derived from the Latin ‘Orient’ (east) because of its restricted distribution in eastern Asia. The phallus, right valve and body coloration show geographic variation.

D. epischista and D. orientalis are within the clade that includes D. heindeli and D. terpsichorella, but the former two species differ in many characteristics, including narrow trapezoidal wings, a flat right valve, and a curved, twisted, and elongated uncus, whereas most species in this genus have broad trapezoidal hind wings.

Original research

Park J, Yagi S, Kobayashi S, Hirowatari T (2024). A new species of the genus Dryadaula Meyrick (Lepidoptera, Dryadaulidae) from Japan, with a redescription of D. epischista (Meyrick, 1936). ZooKeys 1217: 327-342, DOI:10.3897/zookeys.1217.122695

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