A still from my YouTube video at http://youtu.be/_JHI8xgc
No interactions present.
You can't separate the several Lucilia spp. except by examination of the male genitalia.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Lat/Lng: 50.613310321681, -2.4594783782959
OS grid ref: SY675793
A brackish lake that used to be the estuary of the River Wey, now an RSPB reserve.