An online resource based on the award-winning nature guide –

Locust Borers Laying Eggs

locust borer 049A4943

The Locust Borer (Megacyllene robiniae) is so-called because its host tree is Black Locust (Robinia pseudoacacia). Locust Borer larvae tunnel into a tree’s trunk and branches, weakening the tree and making it susceptible to wind breakage. In addition, these tunnels serve as a primary infection site for the wind-borne spores of the fungus Phellinus robiniae, which causes a damaging heart rot disease in Robinia species. If you see a Black Locust with many dead and broken limbs, and/or knotty swellings on the trunk, chances are great that it has been attacked by Locust Borers.

The conspicuous, brightly-colored adults appear when goldenrod is in bloom. Adults are commonly seen feeding on goldenrod pollen. Mating takes place now, in the fall, and eggs are laid  in cracks, wounds and under loose bark of a Black Locust tree. The eggs hatch in about a week, the larvae bore into the inner bark of the tree and each larva makes a small hibernation cell and overwinters there. In the spring the larvae begin to bore into the woody part of the tree, enlarging their tunnels as they grow. By mid-summer they pupate and adult beetles emerge in late summer. Previously confined to the native range of Black Locust in the Northeast, Locust Borers have spread with the trees throughout the U.S. and parts of Canada.


7 responses

  1. Alice Pratt

    Such a beautiful insect causing so much damage…I’ve heard of a Black Locust tree, but all other info was new to me! Thank, you Mary, for contributing to my knowledge!

    September 20, 2017 at 9:12 am

  2. Alice Pratt

    I think there are many of those trees along a street right around the corner from us…will need to check their leaves…cascading flowers in the spring…so pretty!

    September 20, 2017 at 9:16 am

  3. Barry Avery

    Is the Locust Borer a native or an illegal immigrant?

    September 20, 2017 at 9:22 am

    • Native.

      September 20, 2017 at 9:48 am

      • Barry Avery

        I guess I could have looked it up in my old college textbook. Thanks

        September 21, 2017 at 2:27 pm

  4. Stunning photo!

    September 20, 2017 at 9:24 am

  5. “illegal immigrant”. Lol. Sorry I read you blog to forget about Herr Trump. That comment brought me up short.

    Really enjoying your blog and am learning from it. Gonna tell my friends.

    September 21, 2017 at 8:59 am

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s