Chokecherry Fruit Gall Midge

2010 August 21

Chokecherries are a common small tree around here. They have edible[1] fruit that ripens right around the beginning of August, consisting of berries about the size of peas. At least, most of them are the size of peas. Sometimes, while they are still green, a few of the berries become enlarged and distorted. If you cut open one of these enlarged fruits, this is what is inside of them:

The little orange maggots inside evidently eat away the developing seed, and irritate the plant cells to force them to form a gall instead of a proper fruit, with a hollow inside that fills with fluid. It looks like they drink this fluid and get their nutrition from it.

Looking at just one maggot, it looks like there is a clear envelope around the main core of the body, which is orange. There aren’t a lot of physical details, which is typical for gall-forming larvae. After all, even if they had legs and eyes, what would they do with them, sealed inside of a gall like that?

So. I figured, it’s a gall made out of a chokecherry fruit, so a search on “Chokecherry fruit gall” should turn something up. And it did: they are Chokecherry Gall Midges, Contarinia virginianae. It says they are pretty specific to chokecherries and “saskatoons”, which on further investigation turn out to be Amelanchier alnifolia. Saskatoons are also variously called serviceberries, juneberries, or sugarplums, depending on where you are and who you talk to.

The adult form is a midge, which are small flies with a superficial resemblance to mosquitos. The midges probably lay their eggs on either blossoms or very young fruit, with the maggots then getting inside and turning it into a gall while they develop. They then tunnel out of the fruit before it fully ripens, and they drop into the soil to pupate until the next year. Not a very exciting lifestyle, but it works for them. Usually the damaged fruits drop off before the surrounding fruits ripen, so they are generally gone by the time that birds (or humans) come by to pick and eat the ripe fruit. It is definitely to the advantage of the midge larvae to finish up and clear out before anything comes by to eat the fruit, for obvious reasons.

And as for why a maggot that lives its entire life in a dark enclosed place is a bright flaming orange color like that (even though it is unlikely ever to be seen), well, that’s an easy question to answer: I haven’t the slightest idea.

Hey, I said it was easy to answer. I didn’t say the answer would be helpful.

[1] Edible by the standards of “wild foods” aficionados, at any rate. By which I mean, you don’t want to eat them straight off of the tree – they aren’t called “chokecherries” for nothing. They have to be processed to make them actually pleasant to eat, which usually means cooking them down, straining out the juice, and adding loads of sugar to make jelly. At least they aren’t as bad as some nominally-“edible” plants like acorns and burdock, which usually need treatments like boiling in water and changing the water five or six times to leach out the foul-tasting compounds. After reading a “wild foods trailguide” and seeing the measures that the authors are willing to go through to make some plants “edible”, it kind of brings home just how horrible the things that they concede to be “inedible” must be.

4 Responses
  1. August 21, 2010

    Awesome. They are tiny machines designed to do nothing more than ingest and process fructose. They’re like nanobots for fruit.

  2. August 23, 2010

    Whoa, those larvae are cool- I’d not heard of them before.

    Plus, that’s an insightful observation about “edible” wild foods.

  3. Susan permalink
    July 5, 2020

    Than you so much! Very informative and interesting!

  4. Mike permalink
    July 10, 2020

    Chokecherrys are bsxt eaten from the tree. Jams and syrups aren’t that great. Chokecherry wine is good. We’ve always had these little worms on the tree and I always wondered what they were. Great information.

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