Leaf miners: tracks left in leaves

Here are three examples of leafminer tracks.

The first is Chromatomyia primulae (Robineau-Desvoidy, 1851) in a primrose leaf. The 'mine' is white, long and narrow, with frass in conspicuous, widely spaced black lumps. It is harmless to the plant.
Scanned on 25/06/2010. Leaf from a garden plant in Wimbledon.

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This contrasts with the expanding track of Stigmella aurella in a bramble leaf below. This is one of the commonest miners in Britain and again, it is harmless to the plant.
Photo taken 06/04/2010. Leaf from a bramble in a hedgerow in Senni.

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The third is an infected leaf of a Horse Chestnut tree on the southern side of Wimbledon Common, where almost all the leaves were heavily infected by the Horse chestnut leaf miner Cameraria ohridella.

Scanned on 28/06/2004. Leaf from a Horse Chestnut tree on Wimbledon Common

This leaf infection was first discovered in Macedonia in the late 1970s. They were first found established in the UK in the trees on Wimbledon Common in July 2002. Its spread in the UK is being monitored by the Forestry Commission http://www.forestry.gov.uk/fr/INFD-6YUBY5 who have issued an 'Exotic Pest Alert'. This year, in June 2010, the same trees are again heavily infected.

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Besides moths, similar tracks can be left by a number of beetles, flies and sawflies as they grow and feed on leaves before they burst out of the leaf covering (a useful defence). See http://www.leafmines.co.uk/ where I hope that I identified these leafminers correctly.

Christopher Spry

Wimbledon, London

Updated 21:45, 27 June 2010

Ermine moth webs

Christine Havard photographed these 'silk' webs on the hedgerows in a lane in Senni.

 Norman Lowe, the moth recorder of the Brecknock Wildlife Trust, identified them:

These are webs of the 'Bird-cherry' Ermine moth, Yponomeuta evonymella, the larvae of which feed almost exclusively on Bird Cherry, although there are related species on other trees and bushes. So the Spindle Ermine has been in evidence producing similar webs on spindle a few weeks ago. Numbers of both species vary from year to year but in good years they can be very numerous and obvious.

Although the damage seems serious, the Bird Cherry bush generally recovers very quickly. The larvae feed for only a few weeks in June and shortly afterwards the plant produces a lot of new growth and doesn’t seem to suffer any long-term damage. The two species (moth and bush/tree) are both native and have evolved alongside each other for thousands of years. Certainly Bird Cherry is very common.

Interestingly,  on BBC's 'Springwatch' TV program earlier this month, Simon King showed similar pictures of extensive webs made by the 'Spindle' Ermine moth, Yponomeuta cagnagella.


Christopher Spry
Wimbledon, London
21:00, 25 June 2010