Perasis Hermann, 1905

Londt, Jason G. H., 2007, A review of Afrotropical Perasis Hermann, 1905 (Diptera: Asilidae: Laphriinae), Zootaxa 1521, pp. 9-18 : 11-12

Perasis Hermann

Perasis Hermann, 1905: 37 . Type-species: Perasis sareptana Hermann, 1905 , by monotypy, ( Figs 13 wingtip, 27 antenna, 28 wing, 29 thorax).

Saucropogon Hull, 1962: 103 . Type-species: Perasis transvaalensis Ricardo, 1925 , by original designation.

Oldroyd (1970: 244–245) discussed the synonymy of Saucropogon , suggesting that Hull did not see specimens of the Perasis type-species and therefore ‘misinterpreted’ the genus as defined by Hermann.

While Perasis is a fairly distinctive genus its classification within currently accepted subfamilies is somewhat problematic. Oldroyd (1963 1974) placed Perasis in the tribe Laphriini (then including about 25 genera of Laphria -like flies). Papavero’s (1973) preliminary phylogenetic study did much to elucidate the problems. He essentially divided the Laphriini into two subfamilies, the Laphriinae , into which the majority of Oldroyd’s Afrotropical genera of Laphriini were placed, and the Laphystiinae , containing only three Afrotropical genera ( Hoplistomerus , Perasis , and Trichardis ). While in my earlier work ( Londt 1988) I followed Oldroyd’s arrangement, I subsequently ( Londt 2004) decided to adopt Papavero’s ideas and treated Perasis (and its two close relatives) as Laphystiinae . The recent work of Bybee et al (2004) suggests that my shift in thinking may have been premature as molecular evidence appears to show that the Laphystiinae are too closely related to the Laphriinae for these taxa to be considered separate. In addition, as yet unpublished data accumulated by Dr Torsten Dikow (pers. com.) essentially support the results of Bybee et. al. (2004). It appears, therefore, that Perasis , along with Hoplistomerus and Trichardis , should once again be treated as Laphriinae . With molecular tools now being commonly used to assist in the construction of more reliable phylogenies and classifications, it is surely a matter of time before we will be able to adopt a universal classification for the Asilidae that will have general acceptance. In the meantime I believe that Perasis is probably best accommodated in the Laphriinae .

The three genera previously placed in the Laphystiinae can readily be segregated from the other Laphriinae on morphological grounds. For instance, this group is characterized by features of the wing venation, the main character being that vein R2+3 is bent anteriorly at its distal end and joins R1 just before or at C ( Fig. 3 ). These three Afrotropical genera are not adequately separated using existing keys (e.g. Oldroyd 1963 1970 1974), including the most recent key of Londt (1988). Good generic diagnoses, and consequently a good key, will only be possible when all the species within these genera have been adequately reviewed. As this is the first paper in an intended series designed to cover all the Afrotropical species, the following key is considered preliminary and will probably need updating on completion of planned revisions.

Figures

FIGURE 3. Perasis transvaalensis Ricardo, 1925. Topotypic male wing.

FIGURES 13–14. Perasis transvaalensis Ricardo, 1925. Topotypic female terminalia. 13. Ventral. 14. Dorsal. Scale line 1 mm.