Two species of caterpillar on the grey alders

Earlier this afternoon I noticed several caterpillars on two of the Set A grey alders (Alnus incana). There were a few colourful caterpillars munching away on grey alder No. 3 and there were several white “snowflakey” caterpillars on grey alder No. 2. These snowflake caterpillars have been on the alders since at least mid-August and they seem to have some kind of magic power that can prevent a camera from focussing on them. They eat in random patches to leave the leaves full of holes like a Swiss cheese whereas the colourful, curly caterpillars eat in a more systematic fashion, devouring neat sections between veins. These caterpillars stand with their tails sticking up into the air; when I got close to them they gave them a little wave.

Last year there were two or three other species of caterpillar on the alders. Have a look at all the posts tagged with ‘caterpillars’ if you’re interested!

By the way, I’ve no idea what species either of these caterpillars belong to. Leave a comment or drop me an email if you know what they are, please!

Update (July 2010): The black and yellow ‘caterpillars’ are actually larval forms of the hazel or birch sawfly (Croesus septentrionalis).

Posted in Pests and diseases + The treeblog trees

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