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Ditrigona Moore
Type species: triangularia Moore, N.E. Himalaya, China, Taiwan.
Synonyms: Leucodrepana Hampson (type species idaeoides Hampson,
Sri Lanka); Leucodrepanilla Strand (type species sacra Butler = virgo
Butler, Japan).
This genus was revised by Wilkinson (1968) who stated it to be Oriental
with high diversity in the N.E. Himalaya but no representation in Sundaland.
Two, possibly three, species are tentatively assigned to it here. Wilkinson
included Peridrepana Butler in the generic synonymy but the type species,
hyalina Moore (N.W. India), is currently in Drepana Schrank and
was excluded from Ditrigona by Wilkinson. However, the original
description of Peridrepana was clearly based on Ditrigona derocina Bryk,
illustrated by Butler but misidentified as hyalina: for further
explanation see Wilkinson (1968: 410).
The species are usually satiny white, the fasciae grey to brown,
straight in all except a few species. The forewing is never strongly falcate.
The hindwing margin is either straight, with an acute anal angle, or convex. The
antennae are very variable in form: serrate, unipectinate or bipectinate.
In the male genitalia the uncus is bifid or entire, flanked laterally,
usually at a distance, by setose socii. The valves are variably developed but
often small. The saccus is similarly variable but usually elongate, triangular.
The eighth abdominal sclerites are broad, often strengthened laterally by
longitudinal rods.
The female genitalia have the ovipositor lobes simple, the ductus bursae
of variable length, and the bursa has a single signum (an arcuate, sclerotised
ridge) and often an accessory sac. This signum appears to be the most reliable
generic character.
The larvae of three Japanese species are illustrated by Sugi (1987):
they are short, smooth, cylindrical, the body a translucent pale green, the head
black or green. The anal projections are weak only. All feed on Cornus (Cornaceae).
The Bornean species discussed below are associated with Ditrigona on
grounds of the features of the male abdomen that accord generally with the
features listed above. The only female may belong to the second species
described below or be distinct. Its genitalia show some differences from the Ditrigona
type, notably the ovipositor lobes which are bilobed, and the signum which
is an acute spine.
The facies of all three is more as in 'Leucodrepana' serratilinea
Wileman & South (Taiwan, N.E. Himalaya, Burma, Java), excluded from Ditrigona
by Wilkinson. It is currently assigned to Zusidava Walker (Inoue,
1988) but does not accord particularly closely with that genus (defined below)
either. The female genitalia have simple ovipositor lobes and an accessory sac
to the bursa, but the bursa contain two large, acute, spiny signa. Possibly both
this species and the Bornean ones represent further members of the 'white'
generic complex examined by Wilkinson, but more material is necessary to
establish their generic status and to assess a possible alternative relationship
to the generic grouping suggested on Teldenia
Moore, Zusidava may also belong in
this complex, as does Pseudomodesa Warren (type species plenicornis Warren,
New Guinea) where the valves of the male genitalia resemble those of the Bornean
species and the female ovipositor lobes are similarly bilobed.
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