Until 2004, the blue alder leaf beetle Agelastica alni was thought to be very rare in Britain, possibly extinct although there were some historical records from southern England. Then in 2004 it suddenly appeared again in northern England in the Manchester area, Lancashire and Cheshire in 2006 and Yorkshire in 2014. It was found in Wales in 2013 and in southern England in Hampshire in 2014, mainly around Southampton*. I found it myself for the first time in Hampshire in 2015 near Eastleigh.
I searched for it in Wiltshire in 2016 but couldn’t find it (not that I looked that hard) but of course it was only a matter of time before it arrived. So it came as no surprise when I received an email from David Lawman containing a couple of specimens he photographed in Bentley Wood in south Wiltshire on 11th June. Coincidentally the same day I received an email from Anthony Coles containing a photo of a couple of carded vouchers he found on 2nd and 3rd June in Foxham near Chippenham, north Wiltshire. Although in both instances the photos looked pretty convincing, they were a little blurry (and as I’ve only recently taken on the role of county recorder and I’m not an expert on chrysomelids) I passed them onto David Hubble for a second opinion. Dave runs the Bruchidae & Chrysomelidae Recording Scheme and is the author of the Keys to the adults of seed and leaf beetles of Britain and Ireland and the about to be published Leaf Beetles. Dave confirmed by return, as we all suspected, that they were indeed Agelastica alni.
Anthony Coles who found the specimens in Foxham brought them over to me so I could double-check them against my specimen as at this point his looked like the first records for Wiltshire. Previously I’d had to check my voucher against those in the British Entomological and Natural History Society’s collection (BENHS) which because of its previous rarity came from Europe.
Amazingly while Anthony was parking his car, he found another specimen (a male) on the alder in the car park. Literally a stone’s throw from my house. This began to ring some alarm bells in as much as a couple of weeks previously while refurbishing my bathroom I’d found a purpley-blue beetle on the wall of the stairs. Having my hands full I simply potted it and put in the freezer to look at and key out later. This was the 27 May. Also, it reminded me that Iain Perkins who works on Salisbury Plain had sent me a photo of another purple chrysomelid he’d found on the Plain on 24 May.
On the 16 June, I had a quick look in the car park myself and soon found another 5 and rather embarrassingly another 9 on an alder right outside the front of my house. It may well be that my May 27 specimen blew in through the front door rather than the bathroom window as originally thought. Looking at it in more detail it is indeed another alder leaf beetle and Iain’s photo too has been confirmed as Agelastica alni by Dave Hubble.
This may make Iain’s specimen the first recorded in Wiltshire. I say may just in case there are other records I’m unaware of. Anthony’s looks to be the first for VC7 (North Wiltshire) and marks the most northerly record for Wiltshire from that initial introduction from Southampton. That’s a northern expansion of approximately 80 kilometres (50 miles approx) as the crow flies in 3 years. We’re being invaded!
*Hubble, D. (2015). The distribution of Agelastica alni (Linnaeus) (Chrysomelidae) in Hampshire and its relevance to the species’ British status. The Coleopterist 24(1): 53.