Review of the stiletto fly genus Actenomeros Winterton & Irwin (Diptera, Therevidae, Agapophytinae)

Abstract The endemic Australian genus Actenomeros Winterton & Irwin, 1999b is reviewed. Three species are transferred from Nanexila Winterton & Irwin, 1999a: Actenomeros aureilineata (Winterton & Irwin, 1999a) comb. n., Actenomeros intermedia (Winterton & Irwin, 1999a) comb. n. and Actenomeros paradoxa (Winterton & Irwin, 1999a) comb. n. A new species (Actenomeros budawang sp. n.) is described and figured from New South Wales. A key to species is presented.


Introduction
The completely endemic Australasian stiletto fly (Diptera: Therevidae) fauna is composed of 370 described species in 26 genera, exclusively placed in two subfamilies, Agapophytinae and Therevinae (Winterton 2009(Winterton , 2011. A key to genera of the region can be found in Winterton (2011). Actenomeros Winterton & Irwin, 1999b is a small genus of two described species endemic to eastern Australia, previously classified in the poorly defined Taenogera genus-group (Winterton et al. 1999b), but now classified in Agapophytinae (Winterton 2006(Winterton , 2011. Placement of the genus based on morphological characters is problematic with analyses indicating either a close relationship with Taenogerella Winterton & Irwin (Winterton et al. 1999b) or a clade comprising Taenogera Kröber, 1912, Johnmannia Irwin & Lyneborg, 1989and Eupsilocephala Kröber, 1912(Lambkin et al. 2005. Morphological similarities between Actenomeros and Nanexila Winterton & Irwin, 1999a include the presence of subapical anteroventral setae on the hind femur, antennae with a short, cylindrical scape and conical flagellum, flattened frons, wing cell m 3 open, and lack of velutum patches on the femora and gonocoxites. Winterton et al. (1999a) erected the genus Nanexila with three species groups. One of these species groups (i.e. Nanexila atricostalis species group) was considered very different from the other members of the genus, but the lack of males for most species precluded the erection of a separate genus. It was noted though in Winterton et al. (1999b) that females of this species group (specifically N. paradoxa Winterton & Irwin, 1999a) were similar to Actenomeros. Males are now known for N. paradoxa and have the key taxonomic features of Actenomeros. The generic concept of Actenomeros is revised slightly in light of this; synapomorphies for the genus include multiple rows of postocular macrosetae in both sexes, and greatly reduced or absent articulated gonocoxal processes in the male (Winterton et al. 1999b). The gonocoxite has a large horn-like process in the males of the two previously described species of Actenomeros but are absent in the new species described herein (Actenomeros budwang sp. n.) and three species transferred to Actenomeros from Nanexila [i.e. A. aureilineata (Winterton & Irwin, 1999a) comb. n., A. intermedia (Winterton & Irwin, 1999a) comb. n. and A. paradoxa (Winterton & Irwin, 1999a) comb. n.]; this character is no longer considered synapomorphic for the genus. The discovery of this new species described herein from New South Wales increases the number of species in Actenomeros to six.

Material and methods
Adult morphological terminology follows McAlpine (1981) as modified by Winterton et al. (1999a) and Winterton (2006). Genitalia were macerated in 10% KOH at room temperature for one day to remove soft tissue, then rinsed in distilled water and dilute acetic acid, and dissected in 80% ethanol. Preparations were then placed into glycerine, with images made with the aid of a digital camera mounted on a stereomicroscope. Specimen images at different focal points were taken using a digital camera and subsequently combined into a serial montage image using Helicon Focus (©HeliconSoft). Genitalia preparations were placed in glycerine in a genitalia vial mounted on the pin beneath the specimen.
The following collection acronyms are cited in the text:
Comments. Winterton et al. (1999b) noted that this genus superficially resembles Nanexila but is differentiated by 2-3 rows of postocular setae and male genitalic features such as a reduced or absent articulated gonocoxal process and sometimes a large horn-shaped outer process on the gonocoxite. The remaining species in the Nanexila atricostalis species-group (i.e. N. atricostalis Winterton & Irwin and N. jimrodmani Winterton) retained in Nanexila have a well-formed articulated gonocoxal process and can be distinguished from Actenomeros species using the key to Australasian genera in Winterton (2011). The horn-like process on the gonocoxites is only present in A. corniculaticaudus and A. onyx. Males are unknown for A. aureilineata comb. n. and A. intermedia comb. n.; females of these two species are described by Winterton et al. (1999b). Diagnosis. Setae along costal margin elongate, length approximately twice width of costal vein; scutum uniform grey pubescent; articulated gonocoxal process completely absent; process on gonocoxite straight, elongate, not horn-like; ventral lobe of gonocoxite relatively short, anvil shaped, female with two rows of dark postocular macrosetae.
Comments. Actenomeros budawang sp. n. is similar in appearance to A. paradoxa comb. n., suggesting a likely close relationship. The former can be distinguished by the greatly enlarged ventral lobe, lack of 'horn'-like gonocoxal process and complete absence of the articulated gonocoxal process. The scutal chaetotaxy is variable in this species A. budawang sp. n.