Mullein Weevils

As anticipated, Julia and I have been filling our front yard with fruit trees and a vegetable garden, and letting most of the remaining lawn grow into a meadow–not out of laziness but from a desire to turn this sterile mini-landscape into habitat for something. Already, the monotonous carpet of green has given way to an ever-shifting array of flowers, attracting multitudes of nectar- and pollen-seeking bees, flies, and butterflies. The taller plants provide cover for toads and all sorts of insects and spiders, as well as perches for damselflies and dragonflies like this calico pennant (Libellulidae: Celithemis elisa) that showed up yesterday.

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Every additional species of plant that is allowed to grow, whether a native wildflower or a European “weed,” further increases the diversity of our yard by providing food for its own suite of host-specific insects. For the most part, the native plants do a better job of this, but even this meadow dominated by European plants is a tremendous improvement over closely cut grass.

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In the above photo, the yellow flowers are common cinquefoil (Potentilla simplex). I collected some cinquefoil leaf mines here when we first came to look at the house last May, and the adult agromyzid flies emerged four months later, after we had moved in. The white flowers are lesser stitchwort (Stellaria graminea), the presumed host of this chickweed geometer. The big rosette in the middle of the photo is common mullein (Verbascum thapsus), and it’s just beginning to send up what will be a tall stalk covered with yellow flowers. When I peeked down into the center of the rosette yesterday, I found it covered with little brown weevils.

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I’m a sucker for weevils in general, but I thought these furry ones were particularly adorable.

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Can you spot the female in this pile?

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I had never seen these weevils before, but I had a hunch they were connected with something I saw while walking along a trail in Vermont in early August, 2005. A downy woodpecker was pecking open the seed pods on a mullein stalk, and whatever it was finding in there was exciting enough that it let me get within a few feet of it as I watched it forage. Every stalk nearby had similar ragged feeding holes opened up in many of the pods.

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After the woodpecker had left, I opened up one of the intact pods and found a weevil pupa inside.

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I later learned that the larvae of Rhinusa tetra (Curculionidae; formerly Gymnetron tetrum) develop inside the seed pods of common mullein and pupate there when they have finished feeding. A quick check of online photos of this species seems to confirm that this is the weevil currently congregating on the mullein in my yard. I looked at the other mullein rosettes there, and a few others I came across at work today, and every one of them was similarly covered with these weevils.

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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7 Responses to Mullein Weevils

  1. Andree says:

    I fine the mullein to be host to so many bugs that one plant is nearly enough to keep me busy much of the summer.Alder seems to be the same. “Bug-infested” fascinations.

  2. Jim's Blog says:

    I’m not a bug guy, but I find your blog to be exciting! I’m sure more will come about the wevils in time… We have lots of mullein in our area; perhaps I’ll check them for wevils. Keep up the interesting writing, Charley! — Jim Fowler, Greenville, South Carolina

  3. Michael says:

    Your Dragonfly photo is really beautiful. My farm is located on a lake in CT and I love watching the “Dragons” feed by the dozens just around dusk in the gardens come Summer.

  4. Hi Charley: Mullein is one of my favorite medicinal plants. I harvest and dry about 10 of the large leaves each summer to use as a remedy for nasal congestion brought on by winter colds. I pour just-boiled water over a 4×4 inch piece of leaf in a cup and let it steep for 10 minutes…along with a tea bag of some strong-tasting or fruity tea, and a little honey, so I can’t detect the mild bitter taste of the mullein. Within a few minutes, my nose starts running and my sinuses clear. I’m not a professional herbalist, so cannot officially recommend treatments but have been taught to say “If I had a headcold, I’d make myself some mullein tea.” I also need to note that mullein contains some natural blood-thinning coumarins, so it should not be taken by anyone who is on blood-thinning medications (like Coumadin) and it’s not recommended for extended use.

    I make mint / mullein tea bags and give them to my relatives. Mullein also contains a mild soporific (sleep-inducing agent) so some of my friends and relatives enjoy a bit of the tea before bed as a calmative even when they don’t have a cold. With a potent batch (and/or a Pavlovian response?) my nose starts to run as soon as I open the herb jar.

    Thank you for pointing out and photographing the weevils. I’ll look for them, and leaf miners, the next time I find a mullein. Much of my land is very wet, so the only mullein I see will usually be in the gravelly driveway or on the steep, sandy bank by the road. (I don’t harvest the ones by the road, due to car emissions.) My best source of mullein leaves is new housing developments, where the soil has been pushed around the year before, urging the seeds to sprout and the first year rosettes to grow. I only harvest a leaf or two from each plant, then tap an old seedhead into my palm to bring a few “volunteers” back for the unmowed/unused portion of my gravel parking lot.

    Namaste, Laurie DiCesare, Naturalist, Milton, VT

  5. T. N. Thompson says:

    great information, only recently discovered mullein as an incredible herb for all types of respiratory conditions, according to my nephew, a newly licenced naturopathic doctor, it can be drunk as tea, flowers made into cough syrup, or dried and smoked to control bronchial congestion, sounds crazy but if you can handle inhaling smoke it really does clear the lungs. it was used in this way to help with severe coughing spasms of tuberculosis patients years ago. an incredible plant.

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