Elm Seed Bug

Arocatus melanocephalus

Elm Seed Bug

Elm seed bug (Charles Olsen, USDA APHIS PPQ, Bugwood.org)

Elm seed

Elm seed bug (Charles Olsen, USDA APHIS PPQ, Bugwood.org)

Elm Seed

Elm seed bug life stages (Ryan Davis, Utah State University Extension)


  • black and red bug about 1/3 inch long
  • triangular segment between the top part of the wings
  • triangle is black and surrounded by red on the top portion of the wings (see bottom picture, 2nd bug)
  • alternating black and red pattern outside of wings
  • red abdomen on underside

Nesting Habits

  • found in and around buildings in the spring and fall, especially outdoors where elm seeds have accumulated in the spring
  • elm trees


  • elm seeds


  • nuisance: congregate around buildings that have nearby elm trees and elm seeds; can come indoors and annoy occupants
  • overwinter in cracks and crevices in buildings
  • may stain lightly colored materials and emit an unpleasant odor when smashed
  • not a health threat

IPM Recommendations

  • Remove elm trees in the area if possible.
  • Seal cracks that may allow bugs to enter buildings.
  • Vacuum to remove indoor and outdoor populations.
  • Remove elm seeds that have collected around buildings.
  • Remove elm from tree planting lists.
  • Remove volunteer elm while they are small.

For more information, see our Elm Seed Bug fact sheet.