Plagiodera versicolora

These two were both potted between a river and a small lake - lots of willow here and one of them was on Crack Willow Salix fragilis (the other was on comfrey). My only hesitation keying these was the couplet was in the key to genera where I had to decide if they could be genus Chrysomela. The pronotum base was narrower than the elytra base, but was it sufficiently narrower to say it was more than "scarcely narrower" or not? I thought perhaps it was, but the other characters didn't really fit Chrysomela, at least not convincingly (there was some longitudinal unevenness near the side margin but I didn't think it quite fitted the description of an impunctate costa, and neither beetle was as large as 6mm long). I did run them through the Chrysomela key just in case but although they share a lot of features with Chrysomela aenea there were a number of characters that did not match up.

The first two photos below show one beetle and the other three are the other beetle. Both were clearly green, the second a touch more bluey-green than the other.

2x Plagiodera versicolora, Wendling Beck Environment Project (Norfolk, UK), 26th May 2023

The next time I encountered the species I didn't find it particularly easy to key to genus either. One of the issues I had was the couplet in Duff that required me to take the option that includes, "Elytral epipleura... usually narrow, at least posteriorly". I guess "usually" allows for exceptions but this beetle had what looks to me like a particularly broad elytral epipleura, and not narrowing all that much even posteriorly. Anyway, everything else seemed to check out ok for Plagiodera (which I already had expected it to be) including the two-toothed onychium. As a final reassurance re the elytral epipleura I looked online for photos showing this species' underside and found one at the UK Beetles website: sure enough that has a similarly broad elytral epipleura.

2x Plagiodera versicolora showing head front-on, elytral epipleura, elytra and hind tarsal claws, Rushmeadow (Norfolk, UK), 30th April 2024

I found it really hard to see the pair of apicoventral teeth on the onychium - it seems that you have to hold the claw at just the right angle to see them.

2x Plagiodera versicolora showing hind claw(s) at various orientations, Rushmeadow (Norfolk, UK), 21st June 2024

At last I'm getting used to these I think, although the size difference between the next two was so great that I was expecting them to be different species. In fact although the smaller one was about 25% smaller than the larger, it was comfortably above the lower end of the size range given in Duff. I only retained these two but there were several other similar beetles on the willow these were potted off - the others were a similar size to the larger one.

2x Plagiodera versicolora showing face of first and elytral epipleura and hind tarsal onychium of both, Rushmeadow (Norfolk, UK), 24th July 2024