Colourful Leaf Beetle at Nedd
Many beetles cannot be identified from photographs, but this one is, happily, an exception. It was photographed by Anne Nicoll on their croft at Nedd (NC137321) on 20th April 2024.
It is about 8mm long and the colour combination is striking, with a metallic greeny-blue head and thorax and red wing-cases (photos 1-2). This makes it the knotgrass leaf beetle Chrysolina polita.
There are some 300 species of leaf beetles in the British Isles, all herbivores and often associated with particular plants. I have no idea how this one acquired its English name, since it is found mainly on members of the mint family.
C. polita is common and widespread in England and Wales, but much less so in Scotland, especially the North West Highlands. NBN maps only one previous record from West Sutherland, where it was found in some numbers on water mint at Skerricha, NC2350, on 6th October 2021, by Ellen Wilson. ‘New’ to Assynt therefore, and a good find.
Since it hibernates as an adult, it is something to look out for in spring and autumn, especially in damp places where water mint occurs, or elsewhere on cultivated mints, which are frequent as garden escapes.
Ian M. Evans and Gwen Richards
P.S. We were away from Assynt for over a fortnight shortly after this article was drafted. On the day after we got back, 13th May, Gwen found several of these beetles, including a mating pair (photos 3-4), on a cultivated mint in her garden at Torbreck (NC085242). So, we can add a second record to the tally for Assynt.
Photos 1-2 A.Nicoll; 3-4 G.Richards