Tetrameringia

Introduction

Tetrameringia McAlpine, 1960 is a pale clusiine genus known from six species in Australia (T. pubescens McAlpine and T. ustulata McAlpine), Japan (T. borealis Sueyoshi), Africa (T. aethiopica Stuckenberg and T. stuckenbergi Barraclough) and Madagascar (T. distoma (Verbeke)).  Barraclough (2002) estimates that at least ten species occur in Madagascar and about 30 occur throughout forested areas of the Afrotropical Region. Species are often collected around creeks and small streams in shady areas (McAlpine 1960).

Characteristics

As indicated by the generic name, Tetrameringia is defined by four pairs of fronto-orbital bristles, although some aberrant specimens of T. ustulata have only three pairs. The female abdomen is somewhat bulbous basally (or before its midpoint) and strongly narrowed distally, there are two dorsocentral bristles, no dorsal preapical tibial bristles, the bristles are black, and there is no subnotal stripe.

Like other Clusiinae, Tetrameringia can also be characterized by an inclinate anterior fronto-orbital bristle, a small ratio of the length of the ultimate section of vein M to the penultimate, a presutural intra-alar bristle, outstanding bristles on the posterodorsal surface of the fore femur, a jointed distiphallus (entire and bent in some genera), and a posteromedial truncated notch on the vertex (Lonsdale & Marshall 2006).

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Male genitalia of Tetrameringia ustulata. © Owen Lonsdale

Phylogenetics

Phylloclusia is considered the sister-group to the Tetrameringia in the Clusiinae on the basis of male and female genitalic synapomorphies: posterior margin of male sternite 6 setose; surstylus small, thin and subtriangular; inner surface of surstylus without basal projection; distiphallus broken medially and reflexed; ventral shield of phallapodeme raised from shaft (almost entirely reversed in P. quadrivittata); spermatheca pigmented, irregularly-shaped and with minute transverse grooves (smooth and spherical in T. borealis Sueyoshi); spermathecal duct with subbasal attachment to spermatheca (Lonsdale & Marshall, 2006b).  Loss of the hypandrial bristles may be an additional synapomorphy of these genera, but they are also absent in Clusia. 

Externally, both genera differ from other Clusiidae by having inclinate anterior fronto-orbital bristles, two pairs of dorsocentral bristles, a well-developed postvertical bristle, one pair of vibrissae, a small M_1,2 ratio (1.9-2.5), bristles on the posterodorsal surface of the fore femur and no interfrontal or dorsal preapical tibial bristles.  Most species in these genera also usually lack a subnotal stripe and have an irregular row of ventral ctenidial bristles on the male fore and mid femora (Lonsdale & Marshall, 2006b).

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Female internal genitalia: Tetrameringia pubescens McAlpine; T. ustulata McAlpine; Phylloclusia darlingi Lonsdale&Marshall. © Owen Lonsdale.

References

Barraclough, D.A. 2002. A new species of Tetrameringia McAlpine (Diptera: Schizophora: Clusiidae) from Malawi, the third species from the Afrotropical Region. African Invertebrates, 43: 5-10.

Lonsdale, O. & Marshall, S.A. 2006. Redefinition of the Clusiinae and Clusiodinae, description of the new subfamily Sobarocephalinae, revision of the genus Chaetoclusia and a description of Procerosoma gen. n. (Diptera: Clusiidae). European Journal of Entomology, 103: 163-182.

Lonsdale, O. & Marshall, S.A. 2006b. Revision of the genus Phylloclusia (Diptera: Clusiidae: Clusiinae). The Canadian Entomologist (accepted for publication).

McAlpine, D.K. 1960. A review of the Australian species of Clusiidae (Diptera: Acalyptrata). Rec. Aust. Mus. 25: 63-94.