Amerila Walker (Rhodogastria auctorum)
Type species: astreus Drury.
Synonyms: Canopus Walker (praeocc; type species bubo Walker,
Phryganeomorpha Wallengren (type species madagascariensis Boisduval); Amblythyris
Mabille (type species radama Mabille = madagascariensis).
This is a diverse Old World tropical genus with distinctive facies, such
as the shape of the forewing marginal zone, the reduced hindwings, with, in the
male, modified scales along the rather produced tornus. The general coloration
is white, pale pinkish brown or dark brown, with areas of pink on the abdomen
and the legs, darker species tending to be more variegated on the same pattern
theme as pale ones. The antennae have more segments (80) than other Oriental
Arctiinae, resembling the S. American Phaegopterini to which the genus may have
affinities (Kiriakoff, 1950; A. Watson, pers. comm.). The antennae of
both sexes are filiform, finely ciliate.
The species, when alarmed, produce acrid smelling yellow froth from
cervical glands at the anterior of the thorax.
The form of the genitalia of both sexes and the lack of dorsal sac-like
organs associated with the ovipositor lobes indicate that this genus is not
closely related to other Sundanian Arctiinae. The male has a broad, rather
rounded valve with a central hook-like process interiorly and a massive corema
exteriorly; the uncus is small; the juxta is divided into a dorsal plate and a
ventral pocket; the aedeagus has a large, tubular vesica, with several distal
diverticula, one of which is scobinate and bears two large cornuti. The female
has the basal half of the ductus bursae broadly sclerotised; the bursa is
irregular, corrugated, with a row of spines, often broken into separate
sections, associated with a spiral pleat.
Species in this genus have habitually been referred to Rhodogastria Hübner,
based on the S. African amasis Cramer, a species with affinities to the Spilosoma
group (A. Watson, pers. comm.) and remote from Amerila.
Host-plants for the genus have been recorded from several plant
families: Apocynaceae, Asclepiadaceae, Dioscoreaceae, Myrtaceae, Rubiaceae,
Smilacaceae perhaps with some preference for Apocynaceae (Pinhey, 1975; also
below); some species may be polyphagous.
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