Megaselia differens Schmitz, 1948

R. Henry L. Disney & Sabine Prescher, 2015, Three new species of Megaselia Rondani, 1856 (Diptera, Phoridae) from Switzerland, Mitteilungen der Schweizerischen Entomologischen Gesellschaft 88, pp. 295-306 : 295-297

Megaselia differens Schmitz, 1948

Megaselia differens Schmitz, 1948: 394 (male).

Megaselia beyeri Schmitz in Schmitz & Beyer, 1965: 606, syn. n. Aphiochaeta beckeri Dampf, 1924: 36 . Not Wood, 1909.

In the keys to Abteilung IV, Zweite Reihe of Palaearctic species of Megaselia (Schmitz &Beyer 1965) M. beyeri and M. differens are keyed out in the poorly constructed section of couplets 83 to 97. Couplet 83 initiates problems by dividing species with acostal index exceeding 0.49 from those with the CI less than 0.48. This causes M. beyeri to key out at couplet 86 but M. differens to run out at couplet

96. In the keys to the males of species from the British Isles (Disney 1989) these two species both run out at couplet 114, with the distinction between the two being very fine. Namely the slight difference in the costal indexes and the number of bristles on the epandrium. With the examination of further material of this complex, suspicion that M. beyeri was merely avariant of M. differens arose. This was reinforced by the description of M. beyeri noting that the atypically robust hairs below the base of the male’s hind femur are not crowded as in M. beckeri ,but without mentioning that they are indistinguishable from those of M. differens .

Asubset of this complex of species is characterized by the labella of the proboscis being enlarged and with numerous small spinules on their lower faces. These can then be subdivided on the basis of the details of the hypopygia, whether the hairs below the male’s hind femora are unusually robust or at most only moderately robust, as in the common M. altifrons (Wood, 1909) , and whether the haltere knob is yellow or brown. With regard to the hypopygia the tip of the posteroventral lobe of the epandriun is convex in some but concave in others. M. beyeri and M. differens belong to the concave group, with brown haltere knobs and identical hind femora. The supposed difference in the number of epandrial bristles merely represents two ends of acontinuous range of variation. It is concluded that M. beyeri is asynonym of M. differens .The brief (three and ahalf lines) description of the female of M. beyeri did not allow its recognition. However, the female of M. differens has since been described (Disney 2015). As M. beyeri this species has previously been reported from Switzerland.

We report two males from Ticino after aforest fire (Prescher et al. 2002) Waldbrand, 10 June 1997, Moretti (Bek 19.1 & 142, ETHZ, 19- 175, CUMZ, 19-176).