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Chorsia Walker
Gen. rev.
Type
species: maculosa Walker.
Synonyms: Aeologramma
Strand
(type species picatum Butler, Borneo) syn. n.;
Neustrotia
Sugi
(type species japonica Warren, Japan) syn. n.;
Poecilogramma
Butler
(praeocc.;
type species picatum)
syn.
n.;
Pseuderiopus
Warren
(type species albiscripta Hampson; Indian Subregion, Japan, Borneo) syn.
n.
Aeologramma
was
treated previously in this series (Holloway, 1989) in the subfamily Amphipyrinae,
but shares the features of facies and the male and female abdomen used here to
define Chorsia and distinguish it from Oglasa.
It included three Bornean species that must now be transferred to Chorsia:
C.
picatum Butler comb.
n. (endemic);
C.
decolorata Holloway
comb.
n. (endemic)
and C.
albiscripta Hampson
comb.
n. (widespread
Oriental; see above).
The
species assigned to Neustrotia Sugi in Inoue et al. (1982) have facies and male
genitalia characters as in Chorsia, and Neustrotia is
therefore brought into synonymy. The genus was originally placed in the
Acontiinae by Sugi (loc. cit.), though he placed the probably related Microxyla
Sugi
(see p. 413 and note under C. perversa Walker
comb.
n. below)
in the Ophiderinae. Ueda (1984, 1987) investigated Neustrotia in
relation to other Japanese Acontiinae and found it to have several characters
that distinguished it from the other genera studied, including the fused sacculi
of the male genitalia noted below. He inferred it occupied a ‘peculiar
position’ in the subfamily. The higher classification of this whole generic
complex needs resolution and will be revisited when the remaining Noctuidae
parts of this series are in preparation.
The male
antennae are fasciculate and the third segment of the labial palps is a third or
less the length of the second, and very small to the point of invisibility in
the group with the modified uncus mentioned later. The hindwing has vein M2
present but weak and well separated from M3, whereas in Oglasa
it
is more closely associated. One species included here, C.
rufitincta Hampson
comb.
n.,
was in fact originally also described in an amphipyrine genus as discussed
below.
The
forewings are narrower but the facies is normally very similar to that seen in
typical Oglasa, with two darker brown triangles on the costa and a darker brown
area at the anterior half of the distal margin. However, there is often a brown
patch centrally or on the dorsum also, and the reniform is punctate rather than
obliquely lunulate. On the underside there is almost always a subapical white or
paler spot within the uniform dark ground, a feature shared with typical Pseudogyrtona. Something similar is seen in Hypena
Schrank
and allies.
The male
abdomen has a framed pair of coremata, usually basal, on the sternite, the frame
anteriorly rounded and often bilobed posteriorly. The coremata of the type
species are unusually large and dark, and there is a small central apodeme on
the seventh sternite. In Oglasa the frame is broader, the sides
converging slightly towards the posterior. The eighth tergite of Chorsia
has
a narrow central sclerotisation that expands at the distal margin, whereas the
reverse holds in Oglasa or the thickening occurs both anteriorly or
posteriorly. The genitalia are similar to those of Oglasa
except
the valves have the saccular bases broadly adjacent to fused in the centre of
the diaphragma rather than well separated as in Oglasa.
In one group, the uncus has a prominent dorsal process. The aedeagus vesica
varies in breadth and in the number and complexity of the diverticula.
In the
female genitalia (C. hemicyclopis Hampson comb.
n.,
C.
albiscripta,
C.
greenleavesi sp.
n.),
the corpus bursae is generally distinctly scobinate without this scobination
being intensified in a signum as in Oglasa.
The ductus seminalis arises on a tapering, reflexed diverticulum at the base of
the corpus bursae, a feature also seen to some extent in Oglasa.
The ductus is lightly sclerotised over most of its length, and the ostium can be
set just distal to a slight notch or excavation in the posterior margin of the
seventh sternite, whereas the latter is straight in Oglasa.
The
genus may prove to be diverse in the Oriental tropics and warm temperate
latitudes, as it is in Borneo, and certainly requires further study. Two non-Bornean
species that should be transferred are C.
trigona Hampson
comb.
n. (S.
India) and C. trichocera Hampson
comb.
n. (Philippines).
Chey (1994) noted members of the genus as frequent in softwood plantations in
the lowlands of Sabah.
Sugi
(1987) observed that larvae of Japanese species were associated with deciduous
trees, and cited the observation of Nozaki (1987) that the final instar of one
species does not feed and soon enters the soil to pupate; its head capsule is
smaller than that of the preceding instar. He noted that Gardner (1947) had
described a similar phenomenon in C. trigona Hampson
(as Metachrostis
trigona), including significant differences in the structure of the
mandibles of final and penultimate instars, that of the latter being normal with
an entire distal margin and a strong, curved, subapical carina on the inner
face, and that of the former being reduced, with one long and two shorter acute
distal teeth. Both instars are green, the final one immaculate, the penultimate
one with many of the setae arising from black spots. The prolegs of A3 are
absent, those of A4-6 nearly equal. Gardner stated that the final instar did not
feed, and formed its cocoon between leaves almost immediately. The host plant of
C.
trigona was Dalbergia (Leguminosae).
Bell
MS) described the larva of C.
albiscripta,
but this was not included for the species by Holloway (1989). It is cylindrical,
with the prolegs on A3 absent but those on A4 only very slightly reduced. The
head is broader than deep, grass-green, tinged yellow and spotted with groups of
light sepia dots; the setae arise from black dots. The body is smooth, the
segments clearly defined; the primary setae are set on small chalazae,
colourless except for those on A1, A2 and all supraspiracular ones. The colour
is grass-green, with a thin, whitish spiracular line, and variably with a darker
green or maroon dorsal band. Bell did not refer to any differences between the
last two instars. The larva lives fully stretched on the underside of host plant
leaflets or the midrib of the leaf. It pupates on the ground in
a
roomy silken cell containing earth particles, the larva turning pink before
pupation. The host plants were in the genus Dalbergia (Leguminosae)
with the moth showing a preference for climbing species. Robinson et
al. (2001)
additionally recorded Amphicarpaea from the same family.
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