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Pegomya solennis (Diptera: Anthomyiidae), a miner of Sheep's Sorrel (Rumex acetosella)

In the summer of 2003 Rob Edmunds found several blotch mines on Sheep's sorrel (Rumex acetosella) which were not recognised.

Michael Ackland suspected that they were formed by Pegomya species (either P.solennis or P.bicolor), both of which are found on Dock (Rumex) species. Pegomya solennis is much the commoner miner on Rumex.

Two mines were bred to the pupal stage, but one failed to develop further and one was parasitized.

Further mines were found on May 11th 2004, in Fleet, Hants,VC12.

They were large and occupied the whole leaf (as illustrated).

The larva can be clearly seen in this photo, along with scattered frass grains. The larvae of P.solennis and P.bicolor can be distinguished as P.bicolor has a discal front appendage.

If looked for, the eggs of Pegomya species can be seen firmly glued to the leaf at the start of the mine.

The larva emerged from the mine and had formed a pupa by 13th May. The pupa is 5mm long with clearly defined anterior and posterior spiracles.

 

 

It was kept in a specimen container, with no further treatment and an adult male Pegomya species emerged on 6th September.

 The whole fly is interesting in that it has an adventitious extra small cross vein in the wing (indicated with the arrow)

This extra vein is absent in this view of the fly.
It is necessary to examine the genitalia of such diptera in order to determine the species and this was done (as illustrated).

 

 

The species was confirmed by Michael Ackland as Pegomya solennis. A common leaf miner of Dock.

The character of the 5th sternite (shown opposite) in P.solennis (where it differs from P.bicolor) is the fringe of long hairs on the inner margins of the processes; in P.bicolor the apical half of the processes are mainly bare and there are no long setae along the inner margins.

 

 

Images: Rob Edmunds

Michael Ackland and Rob Edmunds, March 2005  

Newsletter of leafmines.co.uk                                                                                    March 2005