The Lithosiinae are the largest subfamily of Arctiidae in the Oriental tropics. In an earlier part of this series (Holloway, 1988; Part 6), it was suggested that the arctiid subfamilies Syntominae, Thyretinae, Ctenuchinae, Euchromiinae all showed reduction or fusion of hindwing veins and therefore might be related. Subsequent work (e.g. Bendib & Minet, 1998; Kitching & Rawlins, 1999; Jacobson & Weller, in press) has indicated a relationship between (and synonymy of) the last two, but within the Arctiinae, and between (and synonymy of) the first two, but in a sister-relationship (Jacobson & Weller) to the Lithosiinae. The paired pheromone glands of females noted by Holloway (1988) as a potential autopomorphy for the Arctiidae have been confirmed as such (Bendib & Minet, 1988; Kitching & Rawlins, 1999).

The sister-relationship between the Lithosiinae and Syntominae is supported unambiguously by the absence of the MSD seta on the larval abdomen. In both subfamilies lower plants, lichens, algae, mosses and liverworts, feature prominently in records of larval diet (Rawlins, 1984; Kitching & Rawlins, 1999), and records from higher plants therefore need to be treated with caution, as the larvae may merely be browsing on lower plants that are epiphytic on the trunks, twigs and even foliage of higher plants (see below). However, Bendib & Minet (1998) consider there is stronger support for grouping the Syntominae with the rest of the Arctiidae, leaving the Lithosiinae as the basal branch.

The systematics of the subfamily has been relatively neglected since the time of Hampson (e.g. Hampson, 1900), particularly in the tropical centre of its diversity. Birket-Smith (1965) attempted to bring some order to the African Lithosiinae. In the Oriental tropics a few individual genera or restricted faunas have been reviewed (e.g. van Eecke, 1930; Roepke, 1946a, b; Cerný, 1993). Most recently, Bendib & Minet (1999) have defined the subfamily and attempted a tribal classification as discussed in the next sections.

Definition of the subfamily

The subfamily is most reliably defined on features of larval morphology (Bendib & Minet, 1999): a mandible modified by a considerably enlarged mola, a basal area specialised for maceration of lower plant tissue (Gardner, 1943); on the labrum the M1 setal bases are well separated ventrad, rather than laterad, from those of the M2 setae.

However, for most genera, particularly in tropical regions, larvae are unknown, hence features of the adult are necessary to identify members of the subfamily. Bendib & Minet (1999) note two adult characters of the abdomen: a tendency for the anterior regions of each segment of A4 to A6 to be unpigmented, usually becoming bluish with chlorazol black; the postspiracular tergopleural sclerite of A1 is absent. Both of these features require dissection to observe, and the second may be a further synapomorphy for the Lithosiinae and Syntominae.

There are a few more traditional characters (Kitching & Rawlins, 1999; Bendib & Minet, 1999) that may enable most Oriental Lithosiinae to be recognised: reduced ocelli or absence thereof (Macrobrochis Herrich-Schäffer is an exception but may be primitive; see Macrobrochis Herrich-Schäffer); fusion of hindwing vein Sc with Rs over some distance (usually to at least the centre of the section of Rs that forms the cell, though the genera in the first section discussed, including Macrobrochis, show this weakly if at all); a tymbal organ where the microtymbals are fine, shallow grooves, each groove associated with a modified scale.

A high proportion of genera has the valve of the male genitalia with a spine-like extension to the sacculus that extends approximately to the apex of the main laimna.

Classification into tribes

Bendib & Minet (1999) attempted to segregate the subfamily into tribes, but again found the most reliably definitive characters were in the larval morphology. For reasons given in the previous section, practical alternatives to adult morphology are needed to help apply this system to the diverse fauna of the tropics.

However, an adult character was used to distinguish three of the tribes they recognised from the rest (the character has not been investigated for the Acsalini, a monotypic tribe from Alaska and the Yukon Territory): the condition of the apodemes of the sternite of A2. However, the interpretation of Bendib & Minet (1999: 243) of the polarity of this character is unclear. In one state (Figs 119, 127, 271, 278, 298, 521 the apodemes are long, usually slender, with anterolateral processes fused to the sternum; in the other (Figs 22, 121), the apodemes are short, usually robust, with more articulation of the anterolateral processes with the sternum. The second state is regarded as apomorphic by Bendib & Minet, but stated also to occur in all non-lithosiine arctiids as well as the Lithosiini, Endrosini and Phryganopterygini. The first state, regarded as plesiomorphic, is restricted to the lithosiine tribes Eudesmiini, Cisthenini and Nudariini. Thus the suggested polarity could equally well be reversed, with long, slender apodemes being apomorphic. As will be seen, the Cisthenini and Nudariini share the apomorphic feature of general spining in the corpus bursae, as distinct from the pair of signa seen in most Lithosiini, the Syntominae and many Arctiinae. A single signum, often amid more general fine scobination, is seen in the first sequence of genera discussed below and also in the Eudesmiini (New World) and the Phryganopterygini (Madagascar; monogeneric) where it is elongate and scobinate (also in some of the Oriental “Agylla” group, such as Hesudra Moore and Ghoria Moore; see Hesudra Moore Gen. rev.). However, general spining is seen in females of the Endrosini (Palaearctic to Oriental but not in Sundaland or eastwards), though it also tends to be concentrated in a large, broad signum (Bendib & Minet, 1999). The Cisthenini and Nudariini also share sclerotisation of the ductus ejaculatorius (best developed in groups of the former), and enlarged paraptergal sclerites (see Cisthenini again, much more developed in the Cisthenini).

Only three of the seven tribes of Bendib & Minet (1999) have been clearly identified in the Bornean fauna: the Lithosiini, the Cisthenini and the Nudariini, and appreciation of a broader range of taxa within these may lead to their redefinition, e.g. the Cisthenini as discussed (see Cisthenini). All will be defined and discussed in the systematic section.

It is possible that the first six rather plesiomorphic genera discussed may be related to the Phryganopterygini, though several of the shared characters appear plesiomorphic, such as strong to moderate ocelli, little fusion of Sc and Rs in the hindwing, R1 not anastomosing with Sc in the forewing, and no loss of radial sector or medial veins. More unusual features shared with at least some of the Oriental genera are the forewing areole (seen in the “Agylla” group of genera but also true Neotropical Agylla Walker) and the longitudinal signum mentioned above. The hindwing venation is also comparable, with all veins usually present from Rs to CuA2.

A number of genera could not be assigned with confidence to any of the three tribes, some because they were represented by only limited material, but mostly because, whilst showing distinct modifications, they did not share any of the definitive features of the tribes. The Eugoa Walker group of genera is held together loosely by characters of venation and female genitalia, but there is no simple feature found unambiguously in all taxa. Of the remainder, three genera have distinct signa, one in the case of Narosodes Moore and two in each of Tampea Snellen and Darantasia Walker, and the others have general spining or lack it, though females of a few (e.g. Blavia Walker) are unknown.

Biology, ecology and biogeography

The larvae, as mentioned above, have mostly been recorded as feeding on most groups of lower plants: lichens, algae, mosses and liverworts. They tend to graze on these wherever they are abundant, such as on moist walls, cliffs and rocks, the trunks and branches of trees and, in very humid biotopes, on leaves. The last locations may frequently have led them to be associated with the tree or plant concerned, and the identity of this gets propagated in the literature as the host-plant, e.g. perhaps many of the records in Yunus & Ho (1980) and Zhang (1994). But it is apparent (Piepers & Snellen, 1904; Sevastopulo, 1940; Issiki et al., 1965; de Worms, 1975; Rawlins, 1984; Carter & Hargreaves, 1986; Sugi, 1987; Common, 1990; Kitching & Rawlins, 1999; Bendib & Minet, 1999) that feeding on higher plants is rare in the group, but noted particularly in the Lithosiini and Nudariini, where withered or living foliage may be eaten. Henwood (1997) observed that several British species that overwinter as larvae may pass through double the number of instars seen in species that don’t (10-12 instead of 5-6). Numbers of instars have been observed to increase under adverse conditions in other Lepidoptera groups (Common, 1990: 32).

Table 1. Percentage of species for Lithosiinae groups amongst various biogeographic and ecological categories as discussed in the text.

The genus Darantasia (see Darantasia Walker) may be a specialist feeder on Rubiaceae; if confirmed, this would be a very unusual feature. As noted above, the genus is bisignate and so could be an early offshoot in the subfamily. The patterning of the wings and other morphological features are unusual. Nishihara (1992a, b) also recorded two species in the Nudariini feeding on living higher plant leaf tissue.

Pupation is usually in a cocoon that incorporates the larval secondary setae, and these may also be incorporated in a palisade around the cocoon or in an open net at a distance from where the pupa is suspended, Cyana Walker being a classic example of the latter (see Cyana Walker). The time from formation of the cocoon to emergence of the adult appears to be remarkably short in Sundanian species, often just a week (Piepers & Snellen, 1904).

Most adults are nocturnal and come to light, though day-flying is noted in the Scaptesyle Walker quartet of genera (see Scaptesyle Walker) and sporadically in most of the tribes of Bendib & Minet (1999).

The group shows some promise for environmental monitoring. It is diverse and, despite the possibility of some uniformity of the larval diet across habitats (moisture and shelter from insolation being potentially critical factors), shows some indication of specificity to forest type, even within the Bornean lowlands (Holloway, 1984a, 1985, 1998a). Indeed, three closely related species in Euconosia Watson (see Euconosia Watson) appear to segregate on lowland forest type. Lithosiines are moderately diverse at middle altitudes but only a few species are characteristic of elevations above 2000m. These tend to be drawn more from the tribes Lithosiini and Nudariini than from the Cisthenini as illustrated by the matrices of habitat preference against biogeographic range type in Table 1. This differential representation with altitude is reflected in a similar response to latitude; for example, the Lithosiini and Nudariini predominate in the European fauna, joined by members of the more strictly temperate Endrosini.

Response to disturbance is also quite marked. The survey of lowland softwood plantations by Chey (1994; see also Chey, Holloway & Speight, 1997) showed that many Lithosiinae can persist in these managed systems, some becoming quite abundant. The Nudariini appear to be particularly successful, with many species of the genera Cyana Walker, Lyclene Moore and Barsine Walker being common. In the Lithosiini a few Brunia Moore, Macotasa Moore and Teulisna Walker persist, and several species of Eugoa Walker are also represented. In Seram, Holloway (1993, 1998a) found that a small number of species, particularly a member of the nudariine genus Cyme Felder and two Lithosiini, persisted in areas disturbed by cycles of shifting cultivation. In open, farmed habitats representation is much lower, usually only one or two species.

Representation in mangrove is also typically low, with Brunia antica Walker the only Bornean species commonly encountered in this habitat; this species also occurs on some remote islands such as the Chagos group in the Indian Ocean where Lithosiinae are otherwise unrepresented. Eugoa mangle sp. n. and Stictane muara sp. n. are rarer species that may be associated with mangrove.

The biogeography of the group as a whole is indicative of poor dispersal ability. In the course of this work, apparently widespread species such as Oeonistis altica Linnaeus have proved to be complexes of geographically more localised species. Only Lobobasis niveimaculata Hampson and Trischalis subaurana Walker range widely through the Indo-Australian tropics, with just two other species, “Eilema” prabana Moore and “Eilema” monochroa Turner, found on both sides of Weber’s Line, the major discontinuity between Oriental and Australasian faunas in the region (Holloway, 1998b). Several genera appear to be endemic to Sundaland (e.g. Garudinistis Hampson, Stictosia Hampson, Euconosia Watson, Malesia van Eecke) or even Borneo (e.g. Mantala Walker, Cyclosodes Hampson, Omiosia Hampson, Quadrasura Gen. n., Nudariphleps Gen. n.), though all of the latter category are rare, monobasic, and will possibly prove to occur elsewhere in Sundaland. The monobasic Neoduma Hampson is only known from the Philippines and Borneo, and Graptasura Hampson is found only in Sulawesi and Borneo, one endemic species in the former and two in the latter.

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