Wednesday, July 24, 2013

Shy critters in showy houses

My son's young maple is sprouting red balloons.

Maple leaf, mature galls.

Zooming in. No two are alike; each houses dozens of tiny mite larvae, Vasates quadripedes.

You can't beat Ma Nature. She's always coming up with new and unusual ways to accomplish her ends. Like the maple gall mites.

For starters, they're relatives of the spiders and the spider mites. So they "should" have 8 legs, right? No. Nor do they have 6, like the insects. A maple gall mite has 4 little legs near her head, to drag around the rest of her long, pale-carrotty body.

Like all mites, she's tiny; you need a strong hand lens to see her. There may be some, scattered near the top of the leaf below; little squiggly things in a group.

The females overwinter under bark scales and in cracks of their maple tree. When warm weather comes, they go looking for a leaf bud and start to feed on the underside. They wear themselves a hole in the leaf, which repairs itself by building an extension on the upper surface, a little room accessible through the hole. So the mite moves in, and lays her eggs, about 80 of them.

(She has mated, after a fashion, or at least managed to get the eggs fertilized, without coming in contact with the male.)
 Mites do not mate with each other; sacs that the male leaves lying around on the leaf surface fertilize the females as she walks around. No wining, dining or song in an Eriophyid’s lifestyle. - From "Garden Friends and Foes".
The larvae hatch and start feeding on the walls of their shelter. The pouch, or gall, turns from green to red. A few weeks later, the fat little larvae have become adults; it's time to head out to find a new leaf and begin the process again. Several generations down the line, the weather turns; the leaves turn yellow and dry; the galls become black and split open. The females abandon their crumbling houses and find places to hide before the winter comes.

And the males? Irresponsibly parading about, randomly dropping sperm packets, like yesterday's socks. Until the winter comes, and puts an end to the fun.

Another leaf, another housing complex.

With all this colonizing of new green leaves, and forcing the tree to build yet another cluster of mite nurseries, the maple is usually unharmed. Gardeners worry; I did when I saw this tree. But there is no need. The tree will be fine, and the mites will provide feed for ladybugs, which eat the aphids, which suck the sap from the tree. It's all good.

And the little red balloons are sort of pretty, reminiscent of a scattering of pomegranate seeds on a salad.


  1. Great informative post. I noticed lots of galls on our trees down here. Quite unsightly at first but your description is giving me a new appreciation of them.

  2. Thank you for solving that mystery for me, though it doesn't alleviate my automatic reaction of revolt upon seeing the infected leaf.

  3. This is interesting and interestingly written. I have seen these red balloons and taken pictures but could not find clear answers about them until now. :)

  4. Well you learn something new every day! Thanks for the info.


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