Oak Processionary Thaumetopoea processionea

This species is occurring in Norfolk much more frequently in recent years. The arrival of two in my garden trap may suggest the species is in the process of colonising.

Once Pale Eggar is eliminated, the tricky challenge is to eliminate Pine Processionary. Most references refer to the comma-shaped marking on the forewings, noting that this is smaller and weaker on Oak Processionary compared to Pine Processionary. In practice I think this mark is rather variable and some individuals are not very clear based on this feature alone. The pale base of the forewings is another pro-Oak character and this could more easily be seen on these examples.

Oak Processionary Thaumetopoea processionae, North Elmham (Norfolk, UK), 12th July 2022

second Oak Processionary Thaumetopoea processionae, North Elmham (Norfolk, UK), 12th July 2022

I don't think it should often be necessary to check the genitalia to identify these, but this knackered individual died pretty quickly after I caught it so I thought I figured it wouldn't do any harm to examine it properly.

male Oak Processionary Thaumetopoea processionae showing genitalia, North Elmham (Norfolk, UK), 19th August 2023

Turning up for the third consecutive year I'm finding it increasingly hard to believe this species isn't breeding locally. I don't generally do well here for migrant moths and this one was in mint condition suggesting it hadn't travelled far.

Oak Processionary Thaumetopoea processionae, North Elmham (Norfolk, UK), 7th August 2024

I'm not currently releasing these after capture (given their pest status) so this one a few days later was definitely a different individual.

Oak Processionary Thaumetopoea processionae, North Elmham (Norfolk, UK), 12th August 2024