How to Identify Male Douglas-Fir Beetles

Douglas fir beetles are an incredibly destructive insect. They fall into the category of bark beetles and specifically attack the Douglas fir. Severe outbreaks of the Douglas fir beetle occur in host trees that have been damaged through wind, fire, drought or severe defoliation. Their populations can expand rapidly and result in short-lived but devastating epidemics. Douglas fir beetles cause damage by boring into the wood of the unhealthy trees and then progressively dying off as they are forced into healthier trees that are harder to consume. Sexing beetles is difficult in the adult stage, but can be done with a microscope and careful observation.

Things You'll Need

  • Microscope
  • Tweezers or laboratory pick
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Instructions

    • 1

      Position the beetle so that it is on its back.

    • 2

      Look closely at the sections that are present on the beetle's underside, known as sternites, which resemble pieces of overlapping armor. Lift them up with either the tweezers or a laboratory pick. Female beetles will be readily identifiable because they will have almost no separation between the sternites.

    • 3

      Notate the shape of the sternites. In the females, they will be slightly pointed, and in the males, they will be decidedly more rounded.

    • 4

      Check between the sternites for the presence of a membrane. Between the sternites there will be an organ present. These are the male sexual organs.