Why midge galls aren't leaf mines

I just put together a blog post explaining this, in case anyone's interested: https://bugtracks.wordpress.com/2022/11/13/can-gall-midges-be-leafminers/

Posted on November 13, 2022 05:54 PM by ceiseman ceiseman


Very informative, thank you! If I may summarize to make sure I understand correctly: The extent of a leaf mine is defined by the activity of the larva feeding between the cuticles, but in midge galls the extent is defined by the response of the plant to the presence of the larva, and does not directly change through the feeding action of the larva. Is that correct?

Posted by dlevitis 4 months ago (Flag)

That's right!

Posted by ceiseman 4 months ago (Flag)

My reading is that these larva never mine the open space they live in, but it forms through a galling action of some sort? That seems like a tough distinction for people to understand. It seems worth including these in a book about leafminers, because people will be using it to learn about insect larva they find living within the walls of a leaf without already knowing it doesn't technically count. Like many gall books include so called 'non-true galls' and use that space to clarify the difference.

Posted by brnhn 4 months ago (Flag)

Thank you for sharing the article! Didn't previously understand the distinction vs. window mining. (A simpler term than what springs to my mind: leaf strip mining.)
I also read the Green Islands post, to better understand this one. Looks like folks could start duplicating observations of green islands to ID as the virus...

Posted by whateverwatcher 4 months ago (Flag)

Yes, @brnhn, in my leaf mine keys I do try to mention mine-like things that can be confused with mines on particular hosts. But I'd like to discourage people from adding observations to the leafminer project if they know they are galls (which has been happening some, though not as commonly as things like window-feeding and leaftying).

Posted by ceiseman 4 months ago (Flag)

@whateverwatcher The causer of the green islands has been determined to be Wolbachia bacteria in some cases, but there is definitely lots more to be learned there.

Posted by ceiseman 4 months ago (Flag)

Great stuff, thank you.
Congrats on ferreting out the arrival of the invasive zig zag sawfly incidentally.

Posted by raycama 4 months ago (Flag)

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