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Allotoma Roepke
Type species: cornifrons Roepke.
This genus was originally described by Roepke in the Notodontidae, with
the assertion that, whilst unsatisfactory, no better family placement could be
discovered. Kiriakoff (1988, Genera Insectorum 217(c): 2) transferred the
genus to Lymantriidae without comment. The family placement is therefore
unclear. Only males are known.
Examination in the course of this work indicates that the genus is not
noctuoid. It lacks a thoracic tympanum. The abdomen lacks lymantriid tymbals.
The forewing venation has M2 arising from the cell closer to M1 than to M3 as in
Notodontidae, but the male abdomen lacks any of the typical notodont features
such as: the paired processes (cteniophores) on the fourth sternite; modification of the eighth segment; socii on the uncus; absence of a
gnathus; a pleated sacculus to the valve; deciduous cornuti in the aedeagus
vesica (Holloway, 1983; Miller, 1991). The antennae are narrowly bipectinate to
the apex, though with some tapering in the length of the rami, and these lack
the terminal setae typical of Lymantriidae.
The wing venation has features that suggest the genus may be bombycoid.
The forewing has the terminal bifurcation within Rs between R2 and R3 as in
several bombycoid families (Holloway, 1987). Using the convention of Holloway,
the venation is:
R1; ((((R2, R3)R4)R5)M1)
This is seen in some Saturniidae, in Eupterotidae, Lemoniidae and
Bombycidae: Prismostictinae, though, in most of these, one radial vein has been
lost, so homologies are unclear.
The hindwing in Allotoma has R1 present as a distinct cross-vein
between Sc and Rs at the midpoint of Rs within the cell, and Sc runs close to Rs
to a point about 3mm beyond the end of the cell, which is short.
However, the genus has features that make it difficult to place in any
particular bombycoid family, such as the presence of a coiled tongue and a
robust frenulum and retinaculum, though these are also present in the monobasic
Australian family Carthaeidae (Common, 1990). The legs are very short, the
forelegs with strong terminal claws and spines at the apices of each tarsal
joint, and the hindtibia with only one apical pair of spurs. The frons has a
crescent-like excrescence, a bit like the nose-leaf of a bat: this is reflected
in the name of the type species.
The genitalia have a robust, undivided uncus and a strong gnathus as in
Carthaeidae. The valve has a harpe on the sacculus. The aedeagus vesica has a
pair of unusual tridentate cornuti.
Nothing is known of the biology, but the frontal protrusion of the head
suggests that eclosion is from a hard cocoon or impacted soil.
Therefore, the best classification possible at present, without erecting
a family specifically for the genus, is Bombycoidea incertae sedis, as
the features shared with Carthaeidae are plesiomorphic. Kenguichardia Holloway
(1987), the other genus placed in such a category, has been suggested to be
noctuoid by Minet (1998), who has located small thoracic tympana in the unique
male.
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