12 October 2021

What's eating the mullein ? Solved - it's Paracorsia repandalis


We occasionally find mullein (Verbascum sp.) growing next to our driveway, mixed i with the milkweed and shrubbery.  It's not something we plant, so is technically a weed, but we tolerate it because it can grow to such magnificent proportions.  The photo above is from 2013.

This year mullein appeared in the same general area, but met a sad fate.  The central "spear" was persistently attacked and eaten, not by the rabbits, but by some insect.


I found some semilunar cuts reminiscent of what Monarch cats do to milkweed -


-  but never found a caterpillar under the leaves (it might feed only at night).   I let the process go on its own for most of the summer, then this past week decided to dig into the central mass.


What I retrieved is a generally formless mass of plant fibers liberally admixed with frass.  I didn't want to remove all of it, but I did finally dissect the "mass of frass" to find this little fellow -


- a semitranslucent larva that doesn't resemble any butterfly caterpillar I'm aware of.  It could be a moth larva, but the overall appearance frankly looks a bit more like a beetle larva than a lepidoptera species -


It looks not unlike the "grubs" that my mom and I used to dig out of rotting stumps in the woods up at Leech Lake to use for fishing bait back in the 1960s. (the color a bit inaccurate in my available-light photo; it was more yellowish in real life).

I have no idea what it is.  It currently is residing in a container with some of that chewed mass plus some fresh leaves in a closed container on our screen porch.  Given the season I would expect it to pupate in anticipation of winter.

A brief internet search didn't yield an answer for me.  Googling mullein + caterpillar results in numerous hits for a "mullein moth" that is native to Europe.  A 1904 article "What ate the mullein?" in Elementary School Teacher didn't offer a definitive answer.

I'd be delighted to hear any suggestions.  Is this important?  Not at all.  Just that curious minds want to know.

Addendum:  SOLVED by reader Kniffler, who found the moth Paracorsia repandalis at the Maryland Biodiversity Project, where these photos were posted:




Credit for all photos to Peter Coffey.  Apparently what I referred to as a "formless mass of plant fibers" was actually composed of trichomes from the leaves (admixed with an abundance of frass).

I'll check in a few days and see if I can find the pupa.

Addendum:  Here's a good article about mullein found by reader Crowboy.

And also I'm wondering if the "cotton" in the bee nest I found in a window back in 2019 was comprised of these trichomes from mullein.  Looks very similar.

16 comments:

  1. https://en.wikipedia.org/wiki/Tenthredo_scrophulariae ?

    ReplyDelete
    Replies
    1. Maybe. If the moth flew here from Europe. (just to clarify, I'm writing this blog from Wisconsin)

      Delete
  2. Garden Swift Moth?

    https://www.agefotostock.com/age/en/details-photo/garden-swift-moth-hepialus-lupulinus-caterpillar-feeding-on-underground-root/GWG-BEV3043

    ReplyDelete
    Replies
    1. Another European species.

      https://en.wikipedia.org/wiki/Common_swift_moth

      Delete
  3. figwort sawfly larva?
    https://www.projectnoah.org/spottings/7677640

    ReplyDelete
    Replies
    1. Tenthredo scrophulariae lives in Belgium.

      Delete
    2. Ahh, I was thinking of the mullein since it is a member of the Scrophularieae family.

      Delete
  4. https://www.jstor.org/stable/993347?seq=1#metadata_info_tab_contents

    ReplyDelete
    Replies
    1. That's the Elementary School Teacher article I cited in the post

      Delete
  5. iNaturalist says its a Diaphania moth, and it does look a bit like a pickleworm (D. nitidalis larva). But the genus mostly eats squashes, cucumbers, etc.
    https://planthealthportal.defra.gov.uk/assets/factsheets/diaphania-indica-nitidalis-hyalinata.pdf

    I am more inclined to guess it's non-native Paracorsia repandalis:
    https://www.marylandbiodiversity.com/view/19618

    Paracorsia is in the same family Diaphania, and it's likely that iNaturalist's AI doesn't see it so much. The photos on that page, both the grub and the effect on the mullein, look very similar to your find.

    ReplyDelete
    Replies
    1. "Diaphania indica, D. hyalinata and D. nitidalis are distributed in the tropical and subtropical regions of South America, Central America and the Caribbean, and in Florida, USA. Although D. hyalinata and D. nitidalis are unable to overwinter in states outside of Florida and, possibly also, Texas, transient populations are recorded spreading further north of Florida in spring and summer." I'd need to take a blanket out to this one on the screen porch if it were a Diaphania.'

      BUT... I think you nailed it with the suggestion of Paracorsia. Info added to the text. Thank you, Kniffler.

      Delete
  6. Hardly an answer but I found this interesting: https://uwm.edu/field-station/mullein-watching/

    ReplyDelete
    Replies
    1. VERY nice link re mullein. Added to the post. Thanx, Crowboy.

      Delete
  7. Are you sure it's not a baby Chestburster?

    ReplyDelete
  8. My mullein seeds are eaten by the Mullein Seed-eating Weevil (Gymnetron tetrum): Munching on mullein

    ReplyDelete
  9. Mullein seeds are eaten by weevils: https://skeetmotis.blogspot.com/2019/07/munching-on-mullein.html Munching on mullein

    ReplyDelete

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