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Boxelder Bugs Active

4-6-17 boxelder bugs 095You may have noticed ½-inch-long black insects with red markings emerging from cracks and crevices inside or outside your home with the recent arrival of warmer weather. These are adult Boxelder Bugs that have been hibernating all winter and have become active with the warming days. They may disappear on days such as today when the weather turns cold again, but they’ll emerge for good in late April or May, just about the time buds on Boxelder trees are beginning to open.

During the spring and early summer they seek out and feed on low vegetation and seeds on the ground. Starting in mid‑July, they move to female seed-bearing Boxelder trees (or occasionally other maple or ash trees) where they lay eggs on trunks, branches, and leaves.  Red nymphs hatch in roughly two weeks, and proceed, like their parents, to feed on Boxelder foliage and seeds by using their piercing-sucking mouthparts. Even if their numbers are large, there is no noticeable feeding injury to these trees.   Come fall both adults and nymphs congregate in large numbers on the south side of trees, buildings and rocks exposed to the sun (only adults survive the winter) before settling in a protected hibernaculum. Boxelder Bugs are most abundant during hot, dry summers followed by warm springs. They do not bite people and are essentially harmless to property.  (Photo: adult Boxelder Bugs in spring; insert – adults and nymphs in fall) Thanks to Jeannie Killam for photo op.

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6 responses

  1. Elaine Schmottlach

    Presumably we should “leave them be” so they can become food for birds, right?

    April 5, 2017 at 9:36 am

    • Right, though I don’t know how tasty they are, even to birds…many insects marked with red are toxic to lots of creatures.

      April 7, 2017 at 11:33 am

  2. Colleen S Katsuki

    But what is the foliage that the box elder bugs are on? It s not box elder. Are they eating whatever it is that they are on?

    April 5, 2017 at 11:28 am

    • I wondered if someone would catch that! They were on a building that was right next to this planted shrub (I don’t know what it was, perhaps a type of cedar?) and the clump on the wall just extended into the bush. I think they were just warming up in the sun!

      April 7, 2017 at 11:51 am

  3. Miriam Richards

    I am so happy to see your post on boxeider bugs. They have invaded my home and I have been living with them all winter long. They fly into my face as I sit reading at night, attracted by the light. I expect they will depart when spring comes and would love to prevent an invasion again next fall and winter. This is the first occurrence in the 35 years I have lived in my house. Do you have any suggestions how to prevent it? I surely would appreciate them.

    Thanks, Miriam Richards

    On Wed, Apr 5, 2017 at 7:47 AM, Naturally Curious with Mary Holland wrote:

    > Mary Holland posted: “You may have noticed ½-inch-long black insects with > red markings emerging from cracks and crevices inside or outside your home > with the recent arrival of warmer weather. These are adult Boxelder Bugs > that have been hibernating all winter and have become a” >

    April 6, 2017 at 1:32 pm

    • Hi Miriam,
      I’m afraid that unless your house is 100% sealed, it’s pretty impossible to prevent a boxelder bug invasion. I found the following instructions, for what they are worth:
      Boxelder Bug Prevention
      In order to prevent boxelder bugs from invading homes, repair holes in window and door screens, seal cracks and crevices with a good quality silicone or silicone-latex caulk and install door sweeps to all exterior entrances.
      When attempting to get rid of boxelder bugs that have already entered a home or building, no attempt should be made to kill them in wall voids because dead insect bodies can attract dermestid beetles. Rather, using a vacuum cleaner to remove them may provide temporary relief. The bag should be removed to prevent the bugs from escaping.

      April 7, 2017 at 11:24 am

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