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Tasta
Walker
Type species: micaceata Walker.
Synonym: Dissophthalmus Butler (type species iridis Butler).
This genus has more obvious affinities with Lomographa than with
the major group with peg-like setae, though analogous peg-like structures on the
valve are one diagnostic feature. The problematic grouping of white species with
an ocellus similar to that of Tasta but on the forewing has already been
discussed under Lomographa.
The species are mostly steely grey blue in colour, the wings traversed
by diffuse darker bands or bands of reflective scales. The strongest reflective
band is submarginal and, on the hindwing, contains a conspicuous ocellus that
straddles vein M3. The underside is a more distinct, iridescent blue, with
darker, duller postmedial (narrow) and submarginal (broad) bands; the ocellus is
lacking. The male antennae are filiform, densely invested with very short cilia.
The retinaculum is small, but short and broad.
The male genitalia provide several diagnostic features: a long, slender
uncus, straight, with a distinct terminal spine and a cavernous base flanked by
small socii. The gnathus is weak, a narrow, ring-like band. The tegumen is long,
slender on each side. The vinculum lacks a strong saccus but resembles the sectinota
section of Lomographa and L. juta in having a bifid process on
the interior of the distal curvature of the vinculum (the position of the saccus).
The valves are elongate, distally almost rectangular, with a narrow costa.
Setation is sparse, but most dense along the ventral margin. The coarsest setae
occur on an arcuate band of slightly more sclerotised lamina that runs from the
apex of the costa to the centre of the ventral margin, then curving back to the
region of the transtilla. The setal bases in this zone are strong, particularly
around the midpoint of the valve where several setae are mounted on slender
digitate processes. The valves bear strong coremata. The aedeagus is small, as
is the vesica: this varies in ornamentation. The eighth sternite and tergite are
triangular, with the intervening membrane rugose, pleated, a feature also seen
in Lomographa, most strongly so in L. sectinota (figured by
Holloway (1982)).
The female genitalia have the basal zone of the bursa narrow, fluted,
and the distal part pyriform enclosing a large stellate signum of the
‘mushroom’ type.
T. argozona Prout (Burma) and T. epargyra Wehrli (W. China) are mainly white
with a broad silvered grey medial band on each wing and a narrower silver
submarginal, that on the hindwing containing the ocellus. The male genitalia
have the valve more generally setose, with a clump of stouter setae subbasally.
There is also spining on the transtillae.
The genus appears to have its centre of diversity in Borneo, though the
faunas of Sumatra and Peninsular Malaysia require further study. The most
easterly species is T. chalybeata (Sulawesi): records of this species
from Borneo have proved to be mistaken (See T.
chalybeata).
Nothing is known of the biology.
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