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Spodoptera
Guenee
Type species: mauritia
Boisduval.
Synonyms: Laphygma
Guenee (type species exigua Hubner, Old World tropics); Prodenia
Guenee (type species retina Freyer = littoralis Boisduval,
Africa); Rusidrina Staudinger (type species rasdolnia Staudinger =
depravata Butler, Japan, China, Korea); Calogramma Guenee (type
species picta Guerin Meneville).
This genus contains
a very high proportion of agricultural pest species (cutworms and armyworms) and
a number of other interesting taxa, one of which is used as an agent for
water-weed control. Much time has been invested in studies of biology, behaviour,
pheromones, migration etc., but surprisingly no attempt has been made to derive
a modern phylogenetic classification as a framework for these observations.
African and New
World taxa have been reviewed by Brown & Dewhurst (1975) and Todd &
Poole (1980b). The genus as a whole is currently under study by Dr I.J. Kitching,
who plans to provide a phylogenetic hypothesis for it.
The species have
dull grey or brown forewings, the males more contrasted than the females, or a
more reticulate, striate pattern, again with minor sexual dimorphism. The
hindwings of the Old World taxa are, with one exception, white, often nacreous,
usually with a narrow brown border, sometimes with the veins distally delineated
brown also.
The male antennae
can be bipectinate or ciliate, the female antennae ciliate.
In the male abdomen
there are no basal hair pencils, but the basal sternite is relatively short,
with narrow, ovate lacunae associated with the apodemes. The eighth sternite has
lateral rods. In the genitalia the valves have basal, external, sometimes double
coremata, unusual in trifines, and seen here only in some Acronictinae, in the
hadenine Tiracola Walker; they are more distal on the valve in Elusa Walker. The
sacculi of the valves lie adjacent, and are sometimes fused along straight inner
margins. The valves have a slight cucullus, with an extremely distal spined
process associated with a less sclerotised zone that passes between cucullus and
sacculus to the ventral notch between the two. Subbasally on or just ventral to
the valve costa is a small ampullate process that, from species to species,
appears to be long if it is close to the costal margin, but very short if
interior to it. Homology of the distal spine to the costal process of higher
trifines, and of the ampullate process to the harpe is a feasible hypothesis,
but requires further investigation. The aedeagus often has sclerotised bands
extending in to the vesica as in some higher trifines.
In the female
genitalia the eighth segment is much expanded into a lightly sclerotised,
greyish membrane bearing a dense layer of scales that is deposited on the egg
mass. The apodemes of the eighth segment are sometimes only vestigial (e.g. in S.
pecten). The ostium and base of the ductus are strongly
and darkly sclerotised; the ductus distally becomes less sclerotised but
scobinate and fluted. This scobination and fluting is seen also in the very
basal part of the bursa. The bursa contains a single short to moderate signum, a
scobinate band; this is another feature that may associate the genus with the
higher trifines.
The larvae are
typical trifines with primary setae only. They are often strikingly marked,
particularly with subdorsal rows of black streaks or lunules, though rarely
colourful. All African taxa, many of which are Oriental also, are illustrated
and described by Brown & Dewhurst (1975) who also give keys to larvae and
some pupae.
Most species are
highly polyphagous, though there is some tendency for them to be either
graminaceous or dicotyledonous feeders. Two more specialist taxa, S. pectinicornis
Swinhoe and S. picta Guerin-Meneville, are described below.
Full synonymies for S.
mauritia Boisduval, S. cilium Guenee and S. pecten are not
given, as several items need checking.
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