One of my students this semester wanted to work with parasites for his semester ecology project and we discussed some ideas. I told him about mistletoe in Arizona and the gall forming insects that you can find all over the desert. This is my favorite gall here:
Creosote gall
Creosote gall! The female creosote gall midge, a type of fly, lays her eggs in a branch of a creosote bush. The presence of the egg/developing larva induces the plant to grow in a strange new way, covering the helpless maggot with the leafy ball you see here. The fly then develops safely inside the plant until it emerges as an adult. Sadly, my student chose not to work with the galls and will be working with the mistletoe instead, but I did end up with one of the galls to photograph. Aren’t they beautiful?
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The Dragonfly Woman 
Cool. I thought there were only oak galls. I love learning new things from your blog.
Nope! Lots of types of galls on lots of different plants! There are some fabulous galls in the world – the creosote galls are far from the weirdest.
In our part of the world, they recently discovered that the larvae of a species of butterfly (Celastrina serotina) feeds on the galls (Eriophyes cerasicrumena and others) that form on Black Cherry (Prunus serotina). The more you look, the better it gets.
Very true! And thanks for sharing. I didn’t know that and I think it’s fascinating.
The natural world is simply incredible.
Agreed! I never ceased to be amazed.
Looks like a natural plant bud, amazing!
I think they’re gorgeous! Glad you like it.
Goodness it looks like a fractal bromeliad! Any idea if that’s caused by just one larva, or several in cahoots?
I love the very idea of a fractal bromeliad! Fabulous. To the best of my knowledge, and I have not investigated this in the scientific literature, it’s a single maggot per gall. I could be wrong about that though! Your questions makes me want to delve into the lit a bit more to find out for sure now…
I can’t believe you had the gall to post that! (Sorry, I had to.)
I’m adding “fractal bromeliad” to my vocabulary. I don’t know how often I’ll have the chance to use it…
Galls can be the result of one insect or many. When I crack open the spherical galls I find on oak leaves, they seem to be the result of a single larvae, but the galls on hickory leaves I get a lot are simply filled with insects in a little colony. Quite fascinating.
Sadly, I’ve never been able to identify any of the gall species I have in my yard.
I am unable to ID most of the galls I come across myself, though I do know a few. There are so many of them that it’s hard to get a grasp on them. And I am happy someone else likes the phrase “fractal bromeliad” as much as I do. :)
So cool! It’s like a mini habitat. The timing (in the plant’s cycle), the way it forms — everything about this relationship is cool.
Isn’t it? The natural world is so amazing!
Ahhhhhh CREOSOTE IS THE BEST!!!!!!!
just go in the middle of the desert and night and you see literally EVERYTHING centers around these bushes :3
I’ve seen everything from albino katydids to mating blister beetles on creosote..
OH yeah these galls are everywhere on the bushes, almost every bush has one ^_^” interesting to know they are caused by midges, I won’t hesitate to dissect one now that I know they aren’t inhabited by hymenoptera hahaha.
Creosote is the best! And yes, go ahead and dissect that gall to see what’s inside! Though you probably don’t have much to fear from a gall wasp anyway. Those guys tend to be SMALL!