Genus Metopina Macquart, 1835

Type species. Metopina galeata (Haliday, 1833: 179).

Almost three dozen species of the cosmopolitan genus Metopina are known. Confusion has been caused by naming species on the basis of descriptions of one sex only. Modern species descriptions should be based on both sexes or the females alone. Males alone should not be named. The discovery of polymorphism among the females of one species (Disney, 1988) revealed that for a Neotropical species a similar morph had been assigned to a separate genus!

The Australasian species are covered by Disney (2003) and the Asian Palaearctic species are covered by Disney & Michailovskaya (2000) and by Liu (2001), who keys species from China, but overlooked a species added by Yang & Wang (1995). Previously known Oriental species were covered by Schmitz (1927) and Disney (1988, 1994, 2003); with the former also recorded since from the Australasian Region and from Arabia (Disney, 2006). In this paper a further eight species, based on females, are described and named, and a key to the females of all species known from the Oriental Region is provided.

The larvae are unusual in having the mandibles fused to the sides of the median tooth (Fig. 4) and the puparium possesses the respiratory-horn tubercles on the eclosion plates, complete with the central weak spot for the penetration of the respiratory horns. However, the latter are short and weakly sclerotised and fail to puncture the central weak spots. The habits of the larvae are poorly known in this genus. Some species from elsewhere feed on decaying organic materials, including vertebrate carrion, and Hölldobler (1928) reported the case of kleptoparasitic trophallaxis in which M. formicomendicula adults solicit food from the ant Solenopsis fugax. Of the species covered below the larvae of M. ciceri inhabit the root nodules of chick peas, possibly feeding on the nitrogen-fixing bacteria.

Review of species. The formal diagnoses are the features employed in the keys below.

The presence or absence of the bristles of the frons between the four, median, supra-antennal bristles (SAs) and the anterior ocellus are important taxonomically. These bristles comprise an anterior (lower) row, of the inner antials (As) and outer anterolaterals (ALs), and a median row (almost level with the anterior ocellus) of the inner pre-ocellars (POs) and the outer mediolateral bristles (MLs). With regard to the colour of the legs there is always a brown patch on the each mid coxa. Likewise the haltere knobs are brown in all the species covered below.

FIGURES 1–2. Metopina females, abdominal tergites: (1) M. bacanae T3-T6; (2) M. blaxteri T4-T7. Scale bar = 0.1 mm.