Megaselia steptoeae Hartop, Brown, & Disney, 2015

Brown, Brian V. & Vendetti, Jann E., 2020, Megaselia steptoeae (Diptera: Phoridae): specialists on smashed snails, Biodiversity Data Journal 8, pp. 50943-50943 : 50943

Megaselia steptoeae Hartop, Brown, & Disney, 2015

Ecology

While trying to attract another species of the extremely species-rich genus Megaselia Rondani, at the Los Angeles County Arboretum, we made an unexpected discovery. Females of M. steptoeae were attracted to crushed individuals of the glass snail Oxychilus draparnaudi (Beck); Mollusca: Oxychilidae ) (Fig. 2 ). These tiny (1.5 mm long) flies were collected at the Arboretum on two occasions and, in each case, they arrived at the injured glass snail quickly after we crushed the snails (40 s and 13 s, respectively). (Fig. 3 ). On 15 August 2018, we collected five flies and on 9 August 2019, we collected 14 flies. As all flies were females and morphological identification of Megaselia species usually requires male specimens, the five flies from 2018 were sequenced to provide identifications. Identification of the female specimen was made by comparing CO1 sequences (DNA barcodes) of known male specimens of M. steptoeae (Biodiversity Index Number BOLD:AAP4678) with those of the snail-attracted females. Of the specimens collected in 2019, three were kept alive in rearing containers with crushed snails, one of which laid eggs near the snails (the actual oviposition was not observed). Two individual larvae appeared to be mature after four days and were reared to the pupal stage, after which they died. On both occasions in the field, we also provided baits of European garden snails ( Cornu aspersum ( Müller); Mollusca: Helicidae ) and various slugs, none of which attracted any phorid flies. Like the ant hosts, injured glass snails were attractive to flies for a relatively brief period of time (about one-half hour).

A third collecting event took place at the Natural History Museum of Los Angeles County Nature Garden on 17 August 2019. Three snails were crushed, attracting a single female M. steptoeae in ten minutes. One of the snails was barcoded to verify the identification as O. draparnaudi .

Figures

Figure 2. Living individual of Oxychilus draparnaudi (Beck).

Figure 3. Female Megaselia steptoeae Hartop et al. feeding on crushed Oxychilus draparnaudi (Beck).