A couple of insects, well, beetles actually, to look out for at the moment!

article written by Jon Cole

Firstly, check out any Alder trees you come across for the Alder Leaf Beetle (Agarostica alni), a small (7-8 mm), dark, purply blue, rather bulbous, beetle (see photos) – easy to spot against on green leaf, usually on the upper surface. After presumed extinction before about 1994 it has expanded rapidly since, firstly in the west midlands and now across much of the south of England, although only recently recorded in Berkshire. Now occasionally in such numbers that leaves of Alders are being shredded (it’s the larvae that do the damage).  Plenty around the lakes at Dinton Pastures and I found some on young Alders at the back of Sainsbury’s car park in Winnersh when I was queuing for oldies-hour during the last week in April. Could be a serious problem in the future.  Probably came in from France but maybe it was never extinct in the first place. Note that the swollen body in the first image belongs to a gravid female full of eggs.  The other photo is of a male.

Secondly, and you might need a lens for this one, a little (5 mm), brown weevil on Sycamore trees (yes, weevils are beetles). Its scientific name is Bradybatus fallax (it has no English name). It feeds mainly on the catkins that are flowering mid April to mid May.  I say brown as it is extremely hard to see on the tree but under magnification it is a rather distinctive creature (see photos). Last year I recorded one at Dinton Pastures, which was only the third record for the UK.  Last week, using a branch-beating technique, I found 6 more specimens. Perhaps this could become yet another immigrant hell bent on destroying our trees, although it’s not known to be a pest elsewhere, but some close relatives are serious agricultural pests. Again, it is the larvae that do the damage.

Posted: June 18, 2020