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Large Yellow Underwing Larvae Crawling On Snow

12-12-16-large-yellow-underwing049a2252The striped caterpillar that is crawling along the surface of fresh snow is the larval stage of a noctuid or owlet moth known as the Large Yellow Underwing (Noctua pronuba). Noctuids are dull-colored, medium-sized, nocturnal moths that are attracted to lights in the summer. They usually possess a well-developed proboscis (mouthpart) for sucking nectar. The Large Yellow Underwing larva is one of many species  known as cutworms that feed on herbaceous plants. Introduced from Europe to Nova Scotia in 1979, this species has since spread north to the Arctic Ocean, west to the Pacific, and south to the Gulf of Mexico.

Larvae sporadically feed through the winter months whenever temperatures are above the mid-40s. The Large Yellow Underwing larva has been nicknamed the winter cutworm and the snow cut-worm for its ability to feed actively when other cutworms are dormant for the winter. Occasionally on warmer winter days, such as we had last week, you see them crawling on the snow.

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12 responses

  1. Huh. How surprising. Where do they hang out when it’s not warm enough for them to be out for lunch? What herbaceous plants are they seeking/finding? I assume that they must have “antifreeze” to protect them when it’s really cold?

    December 12, 2016 at 7:43 am

    • My understanding is that they shelter under tufts of grass and other vegetation under the snow and presumably stay alive by eating some of it.

      December 12, 2016 at 10:04 am

  2. Connie Snyder

    Very, very interesting! But, exactly what herbaceous plants might they be feeding on just now?

    December 12, 2016 at 8:46 am

    • Hi Connie,
      I can’t tell you specifically what plants they eat, but they do find enough vegetation under the snow to keep them alive. Feasting begins in March or April, when it warms up.

      December 12, 2016 at 10:06 am

  3. Kathryn

    He’s cool – literally!

    December 12, 2016 at 10:01 am

  4. Robin Snyder-Drummond

    I didn’t know there were any moths that survived in the snow. Is this any relation to the Winter Moths that eat our trees?

    December 12, 2016 at 9:24 pm

    • No, Robin, they are in two different families.

      December 13, 2016 at 7:40 am

  5. Kathie Fiveash

    I imagine it takes almost no energy to sustain life at very low temperatures. And I just have to say that as a gardener I hate cutworms. They just cut down my seedlings. Finito. When I find them in the soil, I squish them.

    December 12, 2016 at 10:22 pm

  6. Marilyn

    I imagine, as things proceed, the various beings on earth will proliferate wherever the environment suits them. Over the eons, they’ll evolve to a sustainable situation – given that the earth itself is always changing. Human beings are a huge factor here: I tend to resent the alien starlings and english sparrows and the many imported bugs and all. But nature deals with it by adjusting…

    December 13, 2016 at 7:50 am

  7. I’ve just seen Large Yellow Underwing caterpillars on the snow in the UK – didn’t realise they did this, so was pleased to find your post about it! See

    December 10, 2017 at 10:23 am

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