The systematics of the Australasian Dexiini (Diptera : Tachinidae : Dexiinae) with revisions of endemic genera

Abstract

The Dexiini form a significant component of the Australasian tachinid fauna and include species that parasitise mainly larvae of scarabaeid or cerarnbycid beetles . A generic key and keys to species of all endemic genera (some species-groups of Senostoma excepted) are provided . Senostoma is divided into four species-groups (longipes. rubricarinaturn. punctipenne and hirsutilunula). each described and treated separately. The dominant longipes-group is revised (with a species key). and the remaining groups thoroughly reviewed. with putative species concepts identified . Prosena is not revised, but all valid Australasian species are listed, existing species keys assessed, and various taxonomic and nomenclatural difficulties discussed.

The endemic genera (Prosena excepted) are revised from 47 to 85 species (2 nomina dubia included) in 14 valid genera (previously 13). Six new genera are described: Patulifions, Rasiliverpa (based on two species previously placed in Billaea), Cantrellius, Gemursa, Paulipalpus and Effusimentum. Five generic names are newly synonymised: Anatropomyia Malloch, 1930 and Hobartia Malloch, 1930 = Trichostylum Macquart, 1851; Acucera Malloch, 1930 = Geraldia Malloch, 1930; Ola Paramonov, 1968 = Rutilotrixa Townsend, 1933; Macropodexia Townsend, 1933 = Senostoma Macquart, 1847.

In all, 73 species are described or redescribed. These comprise 43 new species described in 13 genera [most notably in Trichostylum (10), Geraldia (12) and Senostoma (7)]. An additional 17 species (each based on inadequate material) are left undescribed, but are diagnosed by inclusion in species keys. Six species names are newly synonymised: Chaetogaster diversa Pararnonov, 1954 = Trixa lateralis Walker, 1849; Ola erasmusi Paramonov, 1968 = Rutilia nigrithorax Macquart, 185 1 ; Austrodexia communis Malloch, 1930 = Dexia appendiculata Macquart, 1851; Austrodexia mixta Malloch, 1930 = Dexia longipes Macquart, 1846; Lasiocalypter nigrihirta Malloch, 1930 = Dexia tessellata Macquart, 1851; Lasiocalyptrina modesta Malloch, 1930 = Dexia testaceicornis Macquart, 1851. Nine new combinations are established: Trichostylum flavicorne (Malloch, 1930); Trichostylum peculiare (Malloch, 1930); Rasiliverpa agrianomei (Mesnil, 1969); Rasiliverpa vicinella (Mesnil, 1969); Geraldia montana (Malloch, 1930); Rutilotrixa insectaria (Paramonov, 1968); Rutilotrixa nigrithorax (Macquart, 1851); Rutilotrixa wilsoni (Paramonov, 1954); Senostoma longipes (Macquart, 1846). A lectotype is designated for Billaea agrianomei Mesnil, 1969.

The relationships of Australasian genera are reviewed. These comprise two main lineages, which have radiated in distinct adaptive zones, utilising larval hosts in separate niches. Thus carinate genera parasitise Scarabaeidae resident in soil, while non-carinate genera attack mainly wood-dwelling Cerambycidae.