The Drepaninae are characteristically the 'hook-tips', though many
genera lack the strongly falcate forewings that this common name refers to.
Others have the forewings bifalcate, with an angle centrally on the distal
margin. The discal markings are often characteristically bipunctate.
The male genitalia exhibit a great diversity of structure, that extends
often to modification of the eighth and sometimes seventh segments. The uncus is
often deeply bifid, but its development is often rivalled or usurped by
the socii that flank it. The valves can also be reduced. The ovipositor lobes of
the female are frequently bilobed or more complexly divided, and the lamellae
vaginales can also be of complex structure. The variety of genitalic structure
can be appreciated from the figures presented here and also from the
illustrations in the papers by Watson referred to later.
The larva has the anal prolegs vestigial, but the suranal plate is
usually produced into a process or processes of variable length, giving the
larva a tailed appearance. The crochets on the other prolegs are arranged in a
mesoseries, together with a short lateroseries. A single verruca or pair of
verrucae may occur dorsally on the thorax (Scoble, 1992).
Within the Drepaninae, authors (e.g. Watson, 1965a, 1967; Minet, 1985;
Scoble, 1992; Minet & Scoble, in press) recognise two subgroups, here
placed at tribal level: the Oretini and Drepanini. Differences in development of
larval secondary setae have already been mentioned. Drepanini larvae are
distinguished by a supracoxal vesicle, possibly glandular, on each side of the
prothorax (Minet, 1985). The adults of Oretini have the tongue reduced or
absent, but it is better developed in Drepanini.
Whilst the Drepanini predominate in the Indo-Australian tropics and are
the only group found in the Palaearctic, the Oretini are dominant in Africa
(Watson, 1965a, 1967). The Drepanini larvae feed on a range of host-plant
families whereas the Oretini show some preference for Rubiaceae. The genera Oreta
Walker, Spectroreta Warren and Amphitorna Turner represent the
Oretini in Borneo (See Oreta
Walker et seq.).
The sequence of genera from Euphalacra Warren to Drapetodes Guenée
in the Drepanini shows a high degree of specialism for palm feeding but with Drapetodes
on gingers (Zingiberaceae). They share a number of adult morphological
features such as a tendency towards bifalcate forewings with strongly oblique,
rather 'ligneous' fasciation, somewhat lamellate even when unipectinate male
antennae, a bifid uncus that is not flanked by socii, single ovipositor lobes,
the lamellae vaginales only weakly modified, and the ductus bursae long and
slender. The larvae of many genera are characterised by spined scoli somewhat
reminiscent of those of Limacodidae.
A further potential grouping of genera includes Macrocilix Butler,
Hyalospectra Warren, Strepsigonia Warren, Canucha Walker, Leucoblepsis
Warren and the new species tentatively associated with Ditrigona Moore
(if not Ditrigona itself). Features common to these genera include: a
tendency towards bifalcate forewings; occurrence of translucent patches in the
postmedial area; a broad, shallow, four-lobed uncus structure; reduced, simple
valves; a pronounced saccus. The three last features give the male genitalia a
characteristic deep triangular appearance. The validity of this grouping
requires further investigation.
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