Periscelididae

Periscelis annulata, copyright Nigel Jones.

Belongs within: Schizophora.

The Periscelididae are a group of small to medium-sized flies with a swollen, caplike pedicel at the base of the antenna. Larvae of Periscelis are associated with sap bleeding from deciduous trees such as oaks or poplars (Mathis & Rung 2010).

Characters (from McAlpine 1987): Small drosophilid-like flies, 3–4 mm long, dull grayish black or brownish black, with milky sometimes brownish-marked wings, and frequently with banded tibiae. Head at least as broad as thorax, distinctly broader than high, and usually higher than long. Postcranium strongly concave above. Frons broader than high, becoming narrower toward bases of antennae; lunule linear, unexposed. Face strongly attenuated between anteroventral extremities of the eyes, usually with a raised plate- or tubercle-like swelling between vibrissal angles, not at all weakened along midline, frequently with hairs on lower portion. Clypeus moderately well-developed; cheek broad, rather strongly bulging posteriorly. Compound eye vertically oval, with short sparse pubescence. One pair of moderately strong frontal, ocellar, inner vertical, outer vertical, and postocellar bristles present; postocellar bristles divergent; distinct vibrissa usually lacking, but a series of relatively strong subvibrissal bristles present along subcranial margin; only a few fine setulae on frons, restricted to lateral margins opposite bases of antennae. Antenna short; pedicel more or less swollen and cap-like, with a dorsal seam and with dorsal surface extended beyond base of first flagellomere; first flagellomere only slightly longer than broad, strongly decumbent, meeting pedicel almost at right angles; arista plumose, with dorsal rays more numerous than ventral ones; two basal aristomeres very short. Proboscis moderately short and stout; palpus small to rather large; labella well-developed. Thorax usually grayish or brownish pruinose, usually with a brown pleural stripe running from in front of anterior spiracle to base of halter. Disc of propleuron bare, usually with one or more proepisternal bristles, but these sometimes absent; proepimeral bristle absent; prosternum narrow, free from propleuron, bare. Scutum with rather sparse short setulae; one postpronotal bristle present; several postsutural dorsocentral, two notopleural, one postsutural supra-alar, and one postalar bristle present; prescutellar acrostichal bristles present or absent; scutellum moderately large and convex, sometimes slightly flattened on disc, with two pairs of bristles, usually without additional setulae, and with apical pair of scutellar bristles longer; prescutellum undeveloped; subscutellum moderately large. Katepisternum with two bristles and additional setulae; anepisternum usually bare, rarely haired; other pleural sclerites bare. Upper margin of anepimeron with two rather large pleural wing processes, the anterior one having a button-like swelling (greater ampulla). Metasternal area usually bare, rarely setulose. Wing short and broad. C without breaks or weakenings beyond humeral crossvein, ending abruptly at R₄₊₅; Sc incomplete, about half as long as R, rather sharply bent forward at end; R₁ usually bare (rarely setose), usually ending in C about middle of wing (rarely deflected to near apex of wing); cells bm and dm present; crossvein r-m joining cell dm at or beyond middle; crossvein dm-cu almost parallel to crossvein r-m; cell cup open or closed posteriorly; A₁ not attaining wing margin. Alula large. Calypteres small; lower one undeveloped. Halter normal, whitish throughout. nLegs fairly short and stout. Fore and mid femora each with a row of fairly strong posteroventral setae. Tibiae usually banded; preapical dorsal tibial bristles undeveloped. Tarsi unmodified. Abdomen rather broad and dorsoventrally flattened. Male with seven pairs of spiracles; first six pairs situated in membrane; seventh pair situated in pregenital sclerite (syntergosternite 7 + 8). Tergite 6 and sternite 6 well-developed, symmetric. Syntergosternite 7 + 8 large, virtually symmetric. Epandrium small and little exposed, setulose above; ventral extremity on each side produced as a surstylar lobe; base of this lobe continuous with epandrium, not articulated. Cerci fairly large, each with an elongate sclerotized anteroventrally directed lobe at apex. Hypandrium rather large, forming a bursa-like chamber; gonopod undifferentiated; paramere in form of sclerotised lobe between base of aedeagus and surstylus-like lobe of epandrium; aedeagus usually rather long and ribbon-like; aedeagal apodeme fused with hypandrium; ejaculatory apodeme large. Female with seven pairs of spiracles. Tergite 7 and sternite 7 fused laterally, enclosing seventh spiracle. Tergite 8 and sternite 8 short and free. Ovipositor short and stout, not at all adapted for piercing. Cerci very short, free from each other. Three sclerotised spermathecae present; these smooth, spherical, with two situated on one duct and one on the other in Periscelis annulata. Egg unusual, blackish brown in color. Larva spiculate, with conspicuous lateral and dorsal projections from all segments. Cephalopharyngeal skeleton with no accessory sclerotized oral rasping surfaces. Each posterior spiracle on a long spiculate conical process arising from extreme caudal margin of terminal segment; this process differing very little in general appearance from adjacent lateral projections. Anterior spiracle small, with four short diverging digits.

<==Periscelididae [Periscelidae, Periscelidinae]
    |--Marbenia peculiaris MR10
    |--Neoscutops rotundipennis MR10
    |--Diopsosoma MR10
    |--Parascutops MR10
    |--Scutops MR10
    |    |--S. chapmani MR10
    |    `--S. fuscipennis MR10
    `--Periscelis WT11
         |--P. annectans Sturtevant 1963 P92
         |--P. annulata MR10
         |--P. annulipes M87
         |--P. flinti WT11
         |--P. occidentalis M87
         `--P. wheeleri M87

*Type species of generic name indicated

REFERENCES

[MR10] Mathis, W. N., & A. Rung. 2010. Periscelididae (periscelid flies). In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado (eds) Manual of Central American Diptera vol. 2 pp. 1087–1092. NRC Research Press: Ottawa.

[M87] McAlpine, J. F. 1987. Periscelididae. In: McAlpine, J. F. (ed.) Manual of Nearctic Diptera vol. 2 pp. 895–898. Research Branch, Agriculture Canada.

[P92] Poinar, G. O., Jr. 1992. Life in Amber. Stanford University Press: Stanford.

[WT11] Wiegmann, B. M., M. D. Trautwein, I. S. Winkler, N. B. Barr, J.-W. Kim, C. Lambkin, M. A. Bertone, B. K. Cassel, K. M. Bayless, A. M. Heimberg, B. M. Wheeler, K. J. Peterson, T. Pape, B. J. Sinclair, J. H. Skevington, V. Blagoderov, J. Caravas, S. N. Kutty, U. Schmidt-Ott, G. E. Kampmeier, F. C. Thompson, D. A. Grimaldi, A. T. Beckenbach, G. W. Courtney, M. Friedrich, R. Meier & D. K. Yeates. 2011. Episodic radiations in the fly tree of life. Proceedings of the National Academy of Sciences of the USA 108 (14): 5690–5695.

Last updated: 2 July 2021.