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Elm Seed Bug (Arocatus melanocephalus)

Detailing the identifying qualities of the Elm Seed Bug, including physical features and territorial reach.

 Updated: 1/25/2017; Authored By Staff Writer; Content ¬©

  Elm Seed Bug  
Picture of Elm-Seed-Bug

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

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.

Elm Seed Bug Information

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

Taxonomy Hierarchy

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

Size, Identifying Tags and Territorial Reach

Size (Adult, Length): Size (Adult, Length): 8 mm to 13 mm (0.312 inches to 0.507 inches)
Identifying Colors: brown, tan
Additional Descriptors: stinky, smelly, swarm, horde, infestation, invasion, cluster, flying, triangle

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

A Note About Territorial Reach: Keep in mind that an insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above. Insects are driven by environmental factors, food supplies and mating patterns and do not nescessarily work within hard-and-fast territorial lines like we humans do.

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