Arctornis Germar

Type species: v-nigrum Fabricius, Europe.

Synonyms: Cassidia Walker (type species obtusa Walker) syn. n.; Chatracharta Walker (type species tortricoides Walker) syn. n.; Ciaca Walker (type species urapterides Walker = rutila Fabricius) syn. n.; Cobanilla Moore (type species marginata Moore) syn. n.; Kanchia Moore (type species subvitrea Walker, India) syn. n.; Lymantralex Collenette (type species heteroides Collenette) syn. n.; Redoa Walker (type species submarginata Walker); Scarpona Walker (type species ennomoides Walker = rutila) syn. n.; Topomesa Walker (type species subinanis Walker = rutila) syn. n.

This genus is extremely diverse in the Oriental tropics, particularly Sundaland, and extends more weakly into the Palaearctic Region and to New Guinea and Australia. Figures in Schintlmeister (1994) suggest that there are at least 46 species in the genus in Sumatra, and the figure for Borneo is approaching twice this. Sketches of the genitalia of unidentified Sumatran species (Schintlmeister, MS) sent to the author have enabled the ranges of some of the new Bornean ones to be extended to Sumatra.

The genus includes as synonyms Redoa, following Heppner & Inoue (1992) and Nielsen, Edwards & Rangsi (1996), and a number of smaller Oriental genera such as Cassidia, Cobanilla, Kanchia, Lymantralex and Scarpona, partly as suggested by Roepke (1948). There are differences in venation across the genus, and there are also some more distinctly (and, in cases, convergently) patterned taxa, but all have the same distinctive features of the male genitalia: an unusual articulated arm, or harpe, often very long and slender, arising from a pocket on the valve sacculus. There may be further ornamentation to the valve margin. The aedeagus is usually short, often flanked by a pair of distinctive lobes or digitate processes. The uncus is variable in form, usually short, broad, sometimes bilobed. The male abdomen has tymbals.

The wings are usually pale-coloured, the majority of the species being satiny white, sometimes with a greenish tinge, or fawn, yellow or shades of brown. The satiny white species often have a rippled effect to the forewing, generated by the distribution and orientation (e.g. ridging) of large, broad scales relative to small, narrow, forked ones (see Holloway (1976)). Sometimes the former are few or absent, giving the wings a translucent appearance. The venation is variable, the forewing with or without an areole, and, when present, variability in how it is formed: the key of Toxopeus (1948) relies particularly on venation characters.

White and pale yellow species are often marked in various ways: rusty brown on the forewing costa, labial palps and frons, and occasionally on the fringes. There may also be a black discal spot, or spots on the legs. The wing veins may also be darkened.

Association of males with females is very difficult, and it is recommended that new taxa be based on males, as these tend to be much commoner in light-trap samples. Some of the minutiae of markings, including those on the palps and legs, may assist in this process, as may the length of the palps and their segments. Therefore, the account of species following will focus almost entirely on males. Females have genitalic features as in the tribal description above, but show some variation in the ovipositor lobes. These can be simple, rather square, or modified by shortening and slight scrolling into arcuate, rather lip-like structures (e.g. Fig 384).

The diversity of the genus in Sundaland, particularly in undisturbed lowland forest (Holloway, 1984), suggests it may, with the Nygmiini, be of importance in monitoring the ecological health of such forests: some species even feed on Dipterocarpaceae (see above and below), and further records of association with this important family of rain forest trees might be predicted.

It is therefore unfortunate that much of the type material relevant to Borneo for species described by Toxopeus (1948) cannot be located. The original descriptions indicate it should be in the Muzium Zoologicum Bogoriense, but several efforts (e.g. by H.S. Barlow and the author in conjunction with MZB staff, as well as by Mackey (1984)) to find it have only been partially successful (Mackey, 1984). Much Toxopeus material in other groups is still extant, including manuscript holotypes in Nygmia and the Lasiocampidae, but it is clear from his 1948 publication that the period during and immediately following the 1939-45 war did not provide the stability conducive to taxonomic research and the preservation of scientific material. Similar problems occurred in Europe during the same period, e.g. in diatom taxonomy (Mann, 1998). The lack of access to type material or its loss can provide a stumbling block to nomenclatural stability in the group concerned, and any attempt to get round this is likely to prove only partly satisfactory.

Toxopeus (1948) provided a key to his new taxa, obviously examined the male genitalia of many of them, but did not illustrate these. The occurrence of approximately twice as many species in Borneo as he was aware of means that the characteristics given in the key may not enable one to identify reliably the species for which type material is missing unless the features concerned are highly distinctive, such as in species like arbor-christi and isabella. Other Toxopeus species based on Bornean material where the type is lacking are adusta, clavigera, erasmia, flaminea, linteola, salebrosa and satinata. A few of these are represented by specimens in BMNH that have been labelled by C.L. Collenette as having been compared with Toxopeus type material. These will therefore be used to establish an identity for the names concerned: adusta, clavigera and linteola. It is likely that some of the four remaining species are redescribed in the species accounts following, but it is important that studies of the genus in the region should not be impeded by a lack of workable taxonomy, even if this should need nomenclatural adjustment later if further types come to light. Some diagnostic features of the four Toxopeus �unknowns� are given at the end of the species descriptions below.

The more distinctive species are treated first, followed by the main mass of satiny white ones, where more detailed descriptions of head and leg features will be included.

The larva of the type species is illustrated in Carter & Hargreaves (1986). It has typically lymantriid secondary setae on verrucae, but those at the posterior,directed backwards, and on the thorax, directed forwards, are distinctly longer. This feature is also seen in the species illustrated by Wang (1993). Possible tribal features have already been mentioned.

Because of the problems of establishing the identity of members of the white group of species, host records associated with named species in the literature should be treated with caution. The genus as a whole in its tropical range has been recorded (Gardner, 1938; Sevastopulo, 1940, 1941; Kuroko & Lewvanich, 1993; Wang, 1993; T.R.D. Bell, MS; unpublished IIE and FRIM records) from the following hosts: Anacardium, Mangifera (Anacardiaceae); Durio (Bombacaceae); Terminalia (Combretaceae); Balanocarpus, Hopea, Neobalanocarpus, Shorea (Dipterocarpaceae); Diospyros (Ebenaceae); Elaeocarpus (Elaeocarpaceae); Alseodaphne, Cinnamomum, Litsea, Phoebe (Lauraceae); Lagerstroemia (Lythraceae); Medinilla (Melastomataceae); Nephelium (Sapindaceae); Camellia, Gordonia (Theaceae).

Bell (MS) indicated that parasitism by tachinid flies was often heavy in S. India.