Photo of the Week – June 8, 2012

I’m sticking with a beetle theme this week, it seems.  My last post focused on the currently ubiquitous soldier beetle.  This one spotlights the dogbane beetle.

A dogbane beetle on a dogbane plant. Lincoln Creek Prairie – Aurora, Nebraska

Read more and see a face-to-face photo of this insect below…

The iridescent green dogbane beetle is so named because both the larvae and adults feed primarily (maybe exclusively?) on dogbane and milkweed plants.  The larvae feed on the roots and the adults feed on the leaves.  Since both dogbane and milkweed plants have the same bitter tasting milky sap, it seems an odd choice of food, but quite a few other insects (including monarch caterpillars) share the same narrow diet, so there must be something good about it.

Because of their relatively large size (about 1 cm in length) and their iridescent color, dogbane beetles are pretty easy to spot in prairies.  For some reason, I usually seem to see and photograph them on plants other than dogbane or milkweed.  Not sure what they’re doing on those other plants…  Regardless, yesterday morning I saw a bunch on dogbane plants, where they belong, so I stopped to take some photos.

They’re awfully cute, aren’t they?

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About Chris Helzer

Chris Helzer is an ecologist and Eastern Nebraska Program Director for The Nature Conservancy. He supervises the management and restoration of approximately 4,000 acres of land in central and eastern Nebraska - primarily along the central Platte River. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press.
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10 Responses to Photo of the Week – June 8, 2012

  1. plant_mgr says:

    How do I differentiate dogbane with Japanese beetle? I know the latter prefers roses but not exclusively. Is the plant preference a clue? Thank you.

    • Chris Helzer says:

      I’m no expert, but I think Japanese beetles are bigger (1.5 cm compared to 1cm for dogbane beetles) have brown elytra (wing coverings) and white spots around their tail end. Other readers may have better characteristics to look for.

  2. Loy Marotz says:

    I found one of these in my yard last year. They are really stiking in their appearance.

  3. James C. trager says:

    The Japanese beetle is quite different in morphological features and even in details of coloring. See the two bugguide images here: http://bugguide.net/node/view/429113.

    The sap chemicals of milkweeds and dogbanes are not identical, and while some feed on both, quite a few insects prefer one or the other, or even appear to be exclusive to either milkweeds or dogbanes.

  4. Ernest Ochsner says:

    They are small jewels in an already stunning beauty, our native prairies.

  5. Karen Hamburger says:

    They are not cute..they are stunningly…BREATHTAKENLY BEAUTIFUL!!!

    Thanks Chris

    Karen

  6. JT says:

    Long time reader, first time writer…
    If feeding exclusively on dogbane/milkweed, as well as, being conspicuous herbivores it’s safe to assume they are sequestering defense chemicals from the plant and saying to the world, ‘don’t eat me, I taste bad.’ One of my undergraduate instructors is the expert on the chemical ecology of Danaus (Monarch’s), here’s a great link, http://homepages.wmich.edu/~malcolm/SM-information/Malcolm-Research.htm.

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