Turnip Sawfly Athalia rosae

I think this is the first species of sawfly that I identified and the one I've recorded most often. On 14th June 2017 I witnessed huge numbers moving along the Norfolk coast, passing me at a rate of at least 100 per minute. I conservatively estimated that during the time I was watching the movement involved at least 10,000 insects but I think others at different coastal sites that day added a couple of zeroes on the end of that number in their estimates. I'm not entirely clear if such coastal movements are immigration events or if the involve dispersing insects from inland sites and built up in numbers at the coast as the sea provides a barrier to their continued dispersal. I suspect the latter.

Turnip Sawfly Athalia rosae, North Elmham Cathedral Meadows (Norfolk, UK), 3rd August 2019

Turnip Sawfly Athalia rosae, North Elmham Cathedral Meadows (Norfolk, UK), 12th August 2019

Turnip Sawfly Athalia rosae, North Elmham Cathedral Meadows (Norfolk, UK), 4th August 2021

Turnip Sawfly Athalia rosae, North Elmham Cathedral Meadows (Norfolk, UK), 7th September 2018

Turnip Sawfly Athalia rosae, Burnham Overy (Norfolk, UK), 5th June 2015

Turnip Sawfly Athalia rosae, Lolly Moor (Norfolk, UK), 10th July 2017

Turnip Sawfly Athalia rosae, North Elmham Cathedral Meadows (Norfolk, UK), 3rd September 2019

Turnip Sawfly Athalia rosae, Wendling Beck Environment Project (Norfolk, UK), 14th May 2022