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Iridescent Dogbane Beetles Emerging

7-1-15  dogbane beetle170Dogbane beetles (Chrysochus auratus) appear suddenly, usually when the plant which they consume and for which they are named is flowering. Look on the leaves and blossoms of Dogbane, or Indian Hemp, (Apocynum cannabinum) for this blue-green beetle with a metallic copper and crimson shine to it.

The iridescence is a special type of color that shines and changes as the insect changes position or we change position looking at it. It is produced by special body structures and light. The surface of the body parts of this beetle is made up of stacks of tiny, slanting plates, under which is a pigment. Some light rays reflect from the surface of the plates, and other light rays reflect from the pigment underneath. At different angles, the light reflects at different speeds, causing interference and resulting in our seeing different colors that shine.

Although all parts of this plant are toxic to humans, Dogbane is tolerated by Dogbane Beetles, whose larvae reside underground where they eat the roots of Dogbane. When they mature into adult beetles, they climb up the plant to the leaves and flowers, which they then consume.

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12 responses

  1. Maury

    Is this the same as the Japanese beetle?

    July 8, 2015 at 7:07 am

    • No, both are beetles, but different families!

      July 8, 2015 at 8:09 am

  2. Roseanne Saalfield

    Mary, good post another good one that would be helpful to me would be about color in birds, especially bluebirds. it’s very hard for me to credit that I am not looking at pigment (or exclusively at pigment) when I look at that startling wonderful blue.

    and another post idea concerns barn swallows. we have many in our barn. bone of great contention between my husband and me. for reasons that would be obvious to any sane human I would like to welcome our swallows to our barn basement only and leave them off the main floor (where we park our cars, store our mowers and tools,). jim disagrees because he wants to offer them as much space for nesting as possible, basement and main floor. I have considered building a mesh wall with a door between the back of the barn (where they principally nest) and the original section (where the cars are) and effectively turning the addition into a bird cage from April – August and then cleaning it all up when they leave. doubtless he’ll not love that idea either but … in cleaning the barn floor yesterday in advance of my older son’s engagement party here in late July (yes I’ll have to clean it at least twice more) I found a failed nest. five dead baby swallows on the barn floor below a collapsed nest. this sad site reminded me that two years ago when we were in a swallow study/barn study conducted by students at Worc Polytech the student who was auditing our barn told me that nationwide there has been an epidemic of collapsing barn swallow nests and no one knew why. I plan to do some research but have you heard anything about this? half the nest is still on the rafter and half on the floor, with the dead babies. it’s only happened to this one nest that I am aware of unless it’s also happened in the basement, a place I do not bother to patrol (btw, even friend Pam Durrant finally convinced Dave to lock the swallows out of their barn. I am not looking at locking them out, only persuading them to go elsewhere. I see some ‘swallow nests’ for sale on the web too. I’ve told Jim we could just hammer in some cheap lumber landing pads in the basement in the proper places and the parents would figure it was a good place for a nest. I think what they like about our main floor is the light, combined with the protection and easy access out to our field. they are a gorgeous, friendly, lovely sight and sound, I grant them that.)

    hope like baby grandson (Otis?) is well and you get to see him plenty,

    Roseanne >

    July 8, 2015 at 7:18 am

    • Hi Roseanne,
      No, I haven’t heard about collapsing barn swallow nests…very peculiar. I’d love to know what you find out about it! The swallows in Harvard are very lucky to have you living there!

      July 8, 2015 at 8:11 am

  3. Connie Snyderr

    Yikes! Have I been mistaking Dogbane Beetles for Japanese Beetles? Looks awfully much like a beetle I routinely smash when found on my roses. Thanks over and over for your consistently fascinating postings.

    July 8, 2015 at 7:49 am

  4. Peter Denis

    We have the look-alike Japanese beetles in southern Quebec who enjoy our roses and Virginia creeper, At the suggestion of a local garden centre we sprayed nemetodes on the groud around the affected plants last fall. So far the Jap. beetles have only appeared in one of the six areas sprayed. Apparently the nemetodes eat the beetle larvae in the ground. Kind of like biological warfare!

    July 8, 2015 at 9:00 am

  5. Do they feed exclusively on dogbane or go after other plants as well? Both flower and beetle are beautiful!

    July 8, 2015 at 3:59 pm

    • Hi Eliza,
      I know they feed on milkweed species, and perhaps other plants as well, but mostly dogbane.

      July 8, 2015 at 10:10 pm

  6. Jane Lucas

    Is it safe to swim in large open areas where a large snapping turtle has been seen?

    July 8, 2015 at 5:17 pm

    • Peter Denis

      I have a large snapping turtle in my pond at the cottage. He/she often spends time in the shade of the Adirondack chairs beside the pond. The turtle watches us while we enjoy an end-of-the-day drink. My understanding is that they are docile until provoked especially in water. One nature guide said that they could be stepped on inadvertently in the water without provoking an attack, but I haven’t tried it. Remember they have very flexible necks which can reach anywhere on their shell. In my experience they will hiss first if being provoked.

      July 8, 2015 at 8:30 pm

      • As I said to Jane (see comments) there probably isn’t a freshwater pond of any size in New England that doesn’t have at least one snapping turtle living in it. They avoid humans — I’ve never known of any swimmer who’s been bothered by one!

        July 8, 2015 at 10:15 pm

    • Definitely. Most ponds of any size have snapping turtles, and they have no more desire to interact with humans than humans have to interact with them!

      July 8, 2015 at 10:09 pm

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