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Orvasca Walker Gen. rev.
Type species: subnotata Walker.
Synonyms: Chionophasma Butler (type species paradoxa Butler,
Australia) syn. n.; Ocybola Turner (type species semifusca Walker,
Australia) ?syn. n.
This is a diverse and widespread genus of mostly small species that is
again best defined on male genitalic characters. The facies is remarkably
variable, including pure white, black and strongly patterned and colourful
types. Some species have facies similar to that of Somena species and
members of the Nygmia atereta Collenette group (See
Nygmia atereta Collenette comb.n). The venation is
similar to that in Somena: vein M2 in the hindwing is lost. M2 is present
in Ocybola, however, so this synonymy, based on genitalic features, is
tentative.
The male genitalia are distinguished primarily by two features: a rugose
protrusion (possibly the gnathus) ventral to the uncus; a flap, possibly
associated with the juxta, between the saccular bases of the valves that
overlaps the saccus. The valves themselves are bifid, often deeply divided, the
bifurcations often rather unequal and always more splayed than in Somena, usually
strongly so, and the upper one may become inturned. The uncus is typically
short, and the aedeagus often has an apical spur.
The female genitalia are variable, but the bursa has a bicornute signum.
The biology of the type species is described below.
The full composition and geographic limits of the genus are still to be
resolved, but it will probably prove to include a high proportion of the smaller
Australasian species. The most easterly species are O. aliena Butler comb.
n. (N. Australia, New Caledonia), O. dolichocera Collenette comb.
n. (Vanuatu) and O. dimorphissima Holloway comb. n. (New
Caledonia). Other species with the generic male genitalic characters are O.
fulvonigra Swinhoe comb. n. and O. lavella Bethune-Baker comb.
n. from the Solomons, O. aurantiaca Hampson comb. n. (N. E.
Himalaya, Peninsular Malaysia (slide 2585)), and O. irrorata Moore
comb. n. (Java: see Somena above for discussion of potential
homonymy).
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