Pegomya winthemi

Pegomya winthemi

These larvae were found feeding in the gills of a Sepia Bolete Xerocomellus porosporus collected on 9th October 2023. The larvae were potted up and most pupated. Extensive googling suggested that the larvae might belong to flies in the family Anthomyiidae but this was later confirmed by keying the emerging adults using Unwin's AIDGAP key to the families of British Diptera and the species identified as Pegomya winthemi (see below).

Pegomya winthemi larvae collected from Sepia Bolete Xerocomellus porosporus, North Elmham (Norfolk, UK), 14th October 2023

Pegomya winthemi larvae collected from Sepia Bolete Xerocomellus porosporus, North Elmham (Norfolk, UK), 15th October 2023

They pupated pretty soon after they left the mushroom.

Pegomya winthemi pupa, North Elmham (Norfolk, UK), 15th October 2023

I think this was the same pupa as photographed above a couple of days earlier, having darkened slightly. Later this pupa became slightly mouldy and no adult fly emerged from it.

Pegomya winthemi pupa, North Elmham (Norfolk, UK), 17th October 2023

A total of 8 adult flies emerged between 4th and 6th November. All were females so there is no genitalic confirmation of the ID but they keyed straightforwardly (once I'd got my head round the bristle nomenclature) to Pegomya using Howard Bentley's Test Key to the Genera of British Female Anthomyiidae and then to winthemi using Michael Ackland key to female Pegomya species.

female Pegomya winthemi showing wing, anepimeron, proepisternal depression, costa from in front, calypters, tergites, mid tibia, arista, prementum (2 angles), hind tarsus and mid tarsus, North Elmham (Norfolk, UK), 4th November 2023