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Jewelweed stem dweller - Pristerognatha agilana

Jewelweed stem dweller - Pristerognatha agilana
Meadow Farm, Winneshiek County, Iowa, USA
October 18, 2016
My notes from 10/18 say "lep larvae in dead/dying stems of jewelweed - occupying parts all the way from hollow rootlets all the way up to thin branchlets. Fly larvae were present in roots, too." Rearing in progress, with caterpillars overwintering in the stems. I really hope this is something other than Endothenia hebesana.

Images of this individual: tag all
Jewelweed stem dweller - Pristerognatha agilana Jewelweed stem dweller - Pristerognatha agilana Jewelweed stem dweller - Pristerognatha agilana


Jewelweed miner id?
Were you able to rear these out? I'm curious what they were.

Hi Catherine
Thanks for your question :)

Nope, my rearing efforts failed for the second year in a row. However, I found pupae in stems in the spring and young larvae of the next generation boring in jewelweed shoots. After doing some digging in the literature, I believe this moth to be Pristerognatha agilana, a tortricid.

I assembled a few key (I think) puzzle pieces on the way to solving this moth mystery over the spring and summer this year, but hadn't yet posted the images to Bugguide. Your question encouraged me to get on the horn and post them, which is now done (it took me a few days to make it happen -- sorry for the tardy reply!).

The identity of this moth is still unconfirmed. However, I strongly suspect it to be Pristerognatha agilana, a tortricid whose close relative in Europe has been documented as a stem borer on Impatiens there. Working in North America way back in 1926, Carl Heinrich published a revision of the moth subfamily to which P. agilana belongs. In those days this species was known as Olethreutes agilana. At the end of his redescription / relisting of this moth, Heinrich mentions that it was known at that time to bore in Impatiens in its home territory of North America:

Type. — In Academy Natural Science, Philadelphia.
Type locality. — Pennsylvania (?)
Food plant. — Impatiens (larva a stem borer)." (1)

That super-brief snippet -- "Impatiens (larva a stem borer)" -- represents, to this day (as far as I can tell), the sum total of all published scientific knowledge about the life history of this animal. Earlier works (such as the original species description) apparently gave no more information than this, and later works seem to have simply parroted this snippet without adding additional details. Where Heinrich got his information is a total mystery to me.

So, if this moth is indeed Pristerognatha agilana, then any information we can collect about its life history beyond what Heinrich wrote will be (as far as I know) new to science!

In my studies this spring I learned that the jewelweed stem borer in my area tends to pupate inside the jewelweed dead stems in spring, emerging straightaway.

Pupation habitat

Unfortunately I only collected a few late-stage larvae and pupae in the spring, and none of them made it to adulthood. As I struggled with my rearing efforts, all the healthy individuals in the wild were eclosing from their pupae as adults, mating, and laying their eggs -- a phenomenon I totally missed! However, by late June I was able to find those adults' young progeny, freshly hatched and doing their thing: boring in the spindly green shoots of this year's crop of jewelweed.

And here's an older larva in an older stem, near the roots, 5 August 2018:

So that's what I was able to find out this year. However, I seem to be transitioning away from insect rearing and documentation work and I am unsure if I will be able to pursue this mystery any further myself. If you have any interest, I'd strongly encourage you to seek out dead jewelweed stems in early spring, confirm that they contain overwintered lep larvae, set up a rearing container indoors with some inhabited stems in it, and attempt to rear adults. If you are successful in rearing adults and they turn out to be Pristerognatha agilana, then yours will be (to my knowledge) the first ever documented rearing of this insect. (Heinrich reported the hostplant but did not cite a source for this information or clearly state that he or someone else had actually reared any adults.)


1. Page 171 in Heinrich, C. 1926. Revision of the North American moths of the subfamilies Laspeyresiinae and Olethreutinae. Bulletin of the United States National Museum 132: 1-216

I'll be in touch late March, or whenever the snow melts.


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