Friday, October 16, 2009

Life's a Beech





This autumn the upper surface of many of the leaves on young beech trees around here are carrying these cylinrical, hairy galls caused by a midge called Hartigiola annulipes that laid its egg in the leaf surface back in the spring. Opening them up reveals the hollow chamber inside with the larva developing down at its base. In a week or two, when it's mature, the gall will separate and fall from the yellowing leaf, shortly to be buried under a carpet of fallen leaves. The larva will pupate there, until the adult midge emerges in spring, at just the right time to lay its eggs in the soft tissue of a newly expanded leaf.



Gall sectioned vertically.....inside, there's a large, hollow chamber



The larva, tucked in here down at the bottom of the gall chamber, still has plenty of room to grow.

6 comments:

  1. That is a fascinating find Phil. I don't think I've ever seen those before.

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  2. Will have to open my own eyes now, you've done your best, thanks.

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  3. Can't say I have ever noticed these before. Is there any plant which is not under attack by something I wonder.

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  4. Hi Keith, John and Adrian,the numbers of these seem to vary from year to year - one particularly group of young beeches was infested but others nearby had escaped. There are two or three similar species with different shaped galls on beech leaves... one, whose name I forget but might be Mykola fagi, produces galls shaped like skittles.

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  5. Nice photo of the larva. I have not seen this species before. I guess I need to look a little harder at our beech trees. I love the way you sliced it in half. When ever I cut into galls I usually find them empty or slice the larva along with it. Thanks, I love to learn something new. I think you might like my post on Leaf Miners at Squirrel's View. That isn't a self promotion, I truly think you will find it interesting.

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  6. Thanks for the comment and the tip-off about the fascinating leaf miners, Sqirrel...........have left a comment on your blog

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