Type species: salicis Linnaeus, Europe.
Synonyms: Candidata Toxopeus (type species subargentea Felder,
S. Moluccas); Charala Moore (type species sericea Moore, India); Laria
Schrank (type species salicis) praeocc.; Leucosia Rambur (type
species salicis) praeocc.; Nymphyxis Grote (type species salicis);
Stilpnotia Westwood (type species salicis).
This is a rather broad concept of Leucoma which may well be
paraphyletic in relation to the next two genera. It embraces all simply white
species in the generic complex that lack the diagnostic features of the other
genera: the deeper wings and accessory veins in the hindwing dorsal area of Dendrophleps
Hampson and the striking sexual dimorphism of Perina Walker. Indeed,
male L. cryptadia Collenette has deeper wings and transparent areas
similar to those of Dendrophleps.
All these genera have an orange-red tinge to the forelegs, parts of the
head and elsewhere. The hind-tibia has only one pair of spurs. The wing venation
is similar in the three genera, though modified in the males of Dendrophleps and
Perina. However, R2 in Leucoma arises independently from the rest
of the Rs system at the cell as in Dendrophleps, but both R2 and R5
branch off near the mid-point of the Rs system, R2 more basally, in Perina.
Many species of Leucoma have an oblique reflective banding on the
forewings parallel to the margin, generated by variation in the orientation of
the scales. This is not seen in the other genera.
All members of the complex show strong asymmetry in the male genitalia,
where the uncus is strong and the valves often relatively small, sometimes with
distal setae that can become enlarged into spines. In the female, the ovipositor
lobes tend to be rather deep. The ductus is unsclerotised, but often basally
broadened, thickened, convolute. It broadens distally into a spherical or ovate
bursa. When a signum is present, it consists of a transverse flange arising from
a sclerotised plate.
Leucoma is most diverse in the Oriental tropics but also occurs in the
Palaearctic Region and extends eastwards to New Guinea and Australia.
The larva of the type species is illustrated by Carter & Hargreaves
(1986). It is black with mixed brown and white setae arising from red verrucae.
There is a row of large cream patches dorsally between the wings of verrucae,
and two cream dashes on each side dorsolaterally.
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