Ectemnius continuus

I don't think this species has a widely recognised vernacular name but Steven Falk's Flickr album has it as Dark Fly Fox.

I initially attempted to key this using the Naturalist's Handbook guide to Solitary Wasps (2nd edition). It took me a while to work out what the differences were in the shape of the pygidium to separate it from genus Crabro, even though I was examining a (much larger) Crabro at the same time (collected from the same Hogweed flowerhead). The specimens weren't in great condition having gone a but mouldy and that didn't help - I ended up clearing both abdomens in potassium hydroxide solution to help clean them up and then I think I could work out what the "gutter" shape was referring to. Misinterpreting the shape of the pronotum I ended up with a choice between cephalotes and lituratus but I couldn't decide between them and it was too small for either. I turned to the RES key and this helped me sort out where I'd gone wrong. The pronotum is quite rounded at the corners when looking from above, but looking from the side helped me to see how it is angled abruptly at the front so that the front face is nearly vertical rather than sloping towards the head as I think it should on the larger cephalotes and lituratus. The forewing was about 5.6mm long.

female Ectemnius continuus showing wings, pygidium, clypeus, thorax from above, thorax and scutellum, pronotum from side and propodeum from side/rear (showing side face to left of photo and rear face to right), Beetley Meadows (Norfolk, UK), 11th July 2025

I collected this wasp with the one above but for some reason managed to separate both the specimen and photos from the previous one so I thought I'd lost it when I examined the first one. I found it shortly after processing the first, but in the meantime had disposed of the first specimen so wasn't able to compare them directly. Nevertheless it was clear from wing measurements and photos that there were obvious differences, this one having a forewing length of 7.7mm, yellow marks on the pronotum and a more extensively yellow scape. I was therefore expecting it to be a different species, or at least a different sex, but keying it out using both keys I can't make it anything else but another female Ectemnius continuus. Photos of this species on the internet show the same range of variation in scape and pronotum markings, though I can't always tell if these involve males or females, so maybe this is just normal variation. I remain uneasy about this though - there is also a subtle difference in the strength of the striations on the mesonotum. For now I'm calling them both continuus, but this time I will retain the specimen so I can revisit it when I get more experience with the genus. In the meantime I will happily take advice from any more experienced hymenopterists reading this. (Soon after processing this I processed what I believe to be Ectemnius literatus. The shape of the pronotum (viewed from the side) was noticeably different; the sculpture of the mesonotum was similar but slightly more finely striated at the rear and more extensively punctured further forward.)

second female Ectemnius continuus showing wings, pygidium, clypeus, thorax from above, thorax and scutellum, pronotum from side and propodeum from side/rear, Beetley Meadows (Norfolk, UK), 11th July 2025