Alder Leaf Beetle Agelastica alni, a Rare Find

e6filmusere6filmuser e6filmuserPosts: 2,622Registered Users Major grins

I encountered this beetle twice (5 & 11 July) on regenerating foliage of an Alder tree at decoy Heath Nature Reserve, in Berkshire. There were at least 5, no more than 6 or 7. It was not in my quite comprehensive guide to British insects, neither was it on the reserve species list. It used to be known as Chrysomela alni.

It was previously believed to be extinct in the UK and is still rare. It was introduced into the USA in the 19th century.

My observations were 6 days apart, nearly half the duration of their feeding period before entering diapause.

The NBN Atlas gives the nearest record as Pewsey, some 60km/30miles (estimated) from where I found it

I had no idea that it was anything special but thought that it would make good images.

The females bulge when they are full of eggs, showing a yellowish orange membrane. The beetles are about 7mm long.

During my first visit they were mostly chewing on the edges of leaves but few were eating on my second visit. The image of the plant allows at least two of the beetles to be spotted (at about 10 o’clock). When not eating, they walk about quite a lot, just fast enough to spoil a framed composition.

Here is an account of the species in Britain:

Olympus EM-1, (aperture priority), Olympus 4/3 50mm f2 macro,F10 or f11, f8 for the plant, hand-held.


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