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  • Elm Seed Bug - (Arocatus melanocephalus)

    Elm Seed Bug - (Arocatus melanocephalus)

    The name and large swarming tendencies of Elm Seed Bugs suggest it is dangerous, but the harmless insect is really just a seasonal nuisance.

    Picture of Elm Seed Bug
    Staff Writer (1/25/2017): First sighted in 2009 in counties in Idaho, the Elm Seed Bug is native to Europe and how it came to North America is unknown. It is a relative of Boxelder Bugs and Stink Bugs, and like them, produces an odor when crushed or smashed. What makes them so troublesome is their swarming nature. Hundreds of them congregate and have a tendency to find their way indoors. They do not harm people, or even the tree they are named after, but the infestation inside a home is naturally disturbing. Because adults do not die in winter, they tend to look for warmer places to ride out the cold weather. They also tend to look for cooler environments in the hot summer, so ridding a house or building of them may be a biannual chore.
    Government agencies in Idaho and Utah suggest vacuuming (using a Shop-vac or other brand of workshop vacuum) any swarms that get inside, and establishing routine insecticide treatments around the perimeter of the house or building as well as window wells, and door frames. Prevention of invasion is easier than removal, so raking up and destroying fallen elm seeds, and inspecting firewood before bringing it indoors are recommended.

    Larval Elm Seed Bugs feed on the seeds of elm trees during the spring and early summer. They are therefore likely to be found in neighborhoods or regions where elms are present.

    Our thanks to Fred and Jan T. in Idaho for their assistance in identifying this insect.

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    Details of the:
    Elm Seed Bug

    Category: True Bug
    Common name: Elm Seed Bug
    Scientific Name: Arocatus melanocephalus

      Kingdom: Animalia
       Phylum: Arthropoda
        Class: Insecta
         Order: Hemiptera
          Family: Lygaeidae
           Genus: Arocatus
            Species: melanocephalus

    Size (Adult, Length): 8mm to 13mm (0.31in to 0.51in)

    Identifying Colors: brown, tan

    Additional Descriptors: stinky, smelly, swarm, horde, infestation, invasion, cluster, flying, triangle

    North American Reach (Though Not Limited To*): Idaho; Oregon; Utah; Wyoming

    * Keep in mind that an insect's reach is not limited by lines on a map and therefore may appear in areas/regions/states beyond those listed above.

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