Periscelididae Oldenberg

Mathis, Wayne N., Rung, Alessandra & Kotrba, Marion, 2012, A revision of the genus Planinasus Cresson (Diptera, Periscelididae), ZooKeys 225, pp. 1-83 : 4-5

Family Periscelididae Oldenberg

Periscelidinae Oldenberg 1914: 41 [as a subfamily of Drosophilidae ]. Type genus: Periscelis Loew, 1858.

Periscelidae . Hendel 1916: 297 [family status].

Periscelididae . Stackelberg 1933: 4 [correct orthography]. Prado 1975: 1-3 [Neotropical catalog]. Mathis and Rung 2011: 359-369 [world catalog].

Diagnosis.

Head: Frons with 1-2 fronto-orbital setae; postvertical setae present and divergent or absent. Pedicel cap-like and with a dorsal cleft, bearing 1 or more dorsoapical setae; basal flagellomere frequently sharply deflexed, arising from ventral surface of pedicel; arista bipectinate. Face uniformly sclerotized and arched, setose laterally.

Thorax: Dorsocentral setae usually 2 (0+2), sometimes 1 (0+1), none presutural; posterior intra-alar seta reduced; scutellum with 1-2 pairs of marginal setae; scutellar disc bare; anepisternal seta usually lacking (present in Planinasus and new genus of Stenomicrinae ). Wing: subcosta rudimentary, not reaching costa, but not fused apically with vein R1; no costal breaks (a weakness in the costa just apicad of the humeral crossvein in Planinasus ); costa extended to vein R4+5 or M; cell dm with a fold running entire length; cell cup present, although vein CuA2 either well developed or extremely reduced. Midtibia bearing a prominent, apicoventral seta.

Discussion.

The concept of Periscelididae , as adopted here, follows D. K. McAlpine (1978, 1983) and includes a few genera previously assigned to Aulacigastridae ( Cyamops Melander, Planinasus Cresson, and Stenomicra Coquillett). McAlpine characterized Periscelididae primarily by the caplike pedicel, which has a dorsal cleft, and its relationship to the basal flagellomere. Although these characters are common to all Periscelididae , they also occur in Neurochaetidae (D. K. McAlpine 1978, Woodley 1982) and other Acalyptrate genera. In a recent phylogenetic study of the Opomyzoidea , using 28S ribosomal DNA and CAD (rudimentary) genes ( Winkler et al. 2010), Stenomicra , Cyamops and Planinasus grouped consistently with moderate support with the genus Aulacigaster and not with Periscelidinae . Moreover, the same analysis failed to find any support for a sister-group relationship between Periscelididae and Neurochaetidae . In an unpublished and comprehensive analysis of the Opomyzoidea , however, the second author found evidence corroborating the proposal of Grimaldi and Mathis (1993), i.e., that the Periscelididae sensu D. K. McAlpine (1983) is the sister-group of the Neurochaetidae . The only non-homoplasious synapomorphy supporting this arrangement is the type of articulation between the pedicel and the basal flagellomere. These results highlight the need to study the phylogeny of these groups further and in greater detail.

Papp (1984) proposed Stenomicrinae for the genus Stenomicra after D. K. McAlpine (1978, 1983) had transferred that genus, together with Planinasus and Cyamops , from the Aulacigastridae to the Periscelididae . Grimaldi and Mathis (1993), Baptista and Mathis (1994), Mathis and Papp (1998), and Mathis and Rung (2011) recognized two subfamilies ( Periscelidinae and Stenomicrinae ) in the Periscelididae , although only the monophyly of Periscelidinae is well corroborated as follows: (1) occiput with a silvery white, microtomentose area immediately adjacent to the posterior margin of the compound eye (secondarily absent in several species); (2) only one fronto-orbital seta, reclinate; (3) mouth opening large (this may be secondarily reduced in Diopsosoma , although this is difficult to determine, given the extreme lateral distentions of the head); (4) costa short, extended only to vein R4+5; (5) vein CuA2 reduced or absent; (6) cell dm with a fold running entire length (also in Stenomicrinae ); (7) postpronotal seta well developed; (8) spiracle 7 ( “stigma”) not free in female postabdomen; (9) several characters of the male terminalia (see Griffiths 1972). The genera comprising Periscelidinae are those that Hennig (1969) included in his more restricted concept of the family, viz: Periscelis Loew, Marbenia Malloch, Neoscutops Malloch, Scutops Coquillett, and Diopsosoma Malloch. Baptista and Mathis (1994) questioned the monophyly of Stenomicrinae and presented evidence that Planinasus might be more closely related to Periscelidinae . Griffiths (1972) considered Diopsosoma Malloch (see also Mathis and Rung 2004) and the small Neotropical genus Somatia Schiner (tentatively in a separate subfamily, the Somatiinae ) to belong in the Periscelididae . Although Mathis and Papp (1992) and Grimaldi and Mathis (1993) questioned the placement of Diopsosoma in the Periscelididae , Mathis and Rung (2004) presented five synapomorphies that confirm its inclusion. Mathis (1993) considered Somatia as closely related to the Psilidae ( Diopsoinea ), while D. K. McAlpine (1997) treated Somatiidae (monotypic) as incertae sedis.

Key to subfamilies of Periscelididae