Allometopon

Introduction

Allometopon Kertesz is a relatively uncommon genus most closely resembling small Sobarocephala and a few pale Clusiodinae, but the anterior fronto-orbital bristle is reclinate, there are no dorsal preapical tibial bristles, and the surstyli are usually relatively large and elaborate. The biology and preferred habitat of this genus are unknown.

Allometopon is predominantly found in southeast Asia, but a few species are known from Japan, Australia and the Seychelles.

Allometopon has 15 described species, but more focused collecting in the Old World tropics will likely uncover numerous undescribed taxa. Because of its ambiguous basal position in the Clusiodinae, establishing the phylogeny of Allometopon will be essential to our understanding of the evolution of the Clusiidae.

Characteristics

Allometopon is smaller than most clusiids (often being less than 4.0 mm in length), and is predominantly yellow with a variable brown pattern, although some species have evolved a brown notum with yellow stripes and spots. Some species also have a minute pair of interfrontal bristles just above the ptilinal suture, which is otherwise found in only a few Hendelia Czerny and Clusiinae.

Externally, Allometopon is the only clusiid with entirely reclinate fronto-orbitals that also has no dorsal preapical tibial bristles. Unlike other extant Clusiodinae, it also has an acute outer angular extension on the pedicel, an extension on the inner margin of the pedicel, a scutellum that is not flattened dorsally, and an elongate, unreduced hypandrial complex (Lonsdale & Marshall in press).

Like species in the Sobarocephalinae, Allometopon has retained a relatively plesiomorphic morphology, strongly contrasting the derived morphology found in other clusiodine genera. Like other Clusiodinae, however, Allometopon also has longitudinally segmented spermathecae, no ventrolateral lobes on the hypandrium, entirely reclinate fronto-orbitals (reversed in Heteromeringia Czerny and Tranomeringia Sasakawa), and no presutural intra-alar bristle (recovered in some Craspedochaeta).

References

Lonsdale, O & Marshall, S.A. In press. Redefinition of the Clusiinae and Clusiodinae, description of the new subfamily Sobarocephalinae, revision of the genus Chaetoclusia and a description of Procerosoma gen. nov. (Diptera: Clusiidae). European Journal of Entomology.