Megaselia speiseri Schmitz, 1929

Disney, R. H. L. & Russell-Smith, A., 2014, Additions to the British list of Megaselia Rondani (Diptera: Phoridae), including two new species, from the crowns of ancient pollarded trees, Journal of Natural History 49 (25), pp. 1599-1626 : 1612-1615

Megaselia speiseri Schmitz

( Figures 17–21 )

Megaselia speiseri Schmitz 1929, p. 124 (male)

The male of this species is covered by the key to British species ( Disney 1989). In the keys to the Palaearctic species, it is keyed out in Abteilung V ( Schmitz and Delage 1974) and described in Schmitz and Delage (1981). However, the costal index varies across the division between those species with a costal index less than 0.44 (Abteilung V) and those whose costal index is O.44 or more. Specimens with the longer costal index fall within Abteilung IV, Erste Reihe, whose species were keyed by Schmitz (1958). M. speiseri will run to couplet 15 in this key. The males of the species of this couplet, along with others, are covered by Disney (1989). Hitherto the female of this species has remained unknown. It is described below.

Female

Head similar to male but labrum ( Figure 17 ) about 1.5 times wider than diameter of postpedicel. Labella paler, with submarginal pale greyish bands above and only about a dozen, widely spaced, bristles reduced to small spinules below and at tips. Otherwise head similar to male. Thorax as in the male in that it has three notopleural bristles, 0–9 (mean: 5) hairs on mesopleuron and the scutellum with an anterior pair of hairs (about as strong as those in middle of scutum) and a posterior pair of bristles. Abdominal tergites brown. T3–T6 as Figure 18 . Terminal segments as in Figure 19 . Venter grey, and typically with hairs below segments 3–6, but sometimes none on 3, Sternite 7 and lobes at rear of sternum 8 as Figure 20 . Cerci brown and at most 1.5 times as long as broad. Furca not evident. Dufour’ s crop mechanism as in Figure 21 . Legs similar to male. Wing as in male except 1.3–1.6 mm long. Costal index 0.44–0.46. Costal ratios 2.5–4.2:1.1–1.5:1. Costal cilia 0.06–00.09 mm long. With two to three axillary bristles, the outermost being longer than the costal cilia. Otherwise it and haltere as male.

Comment

Variation in the number of the relatively few hairs on the mesopleuron includes a single female with a bare mesopleuron. A male with such a bare mesopleuron will fail to key out in the key to the males recorded from the British Isles ( Disney 1989), or else its hypoppygium (loc. cit. fig. 318) obviously differs from those it may run to in the key, especially in having more than nine hairs on each cercus.

Figures

Figure 17. Megaselia speiseri female, proboscis and palps.

Figure 18. Megaselia speiseri female. details of abdomen, tergites 3–6.

Figure 19. Megaselia speiseri female, terminal segments and cerci.

Figure 20. Megaselia speiseri female, sternite 7.

Figure 21. Megaselia speiseri female, Dufour’s crop mechanism (anterior end to right).