Abstract
The concern caused by extensive killing of marketable Douglas-firPseudotsuga menziesii(Mirb.) Franco, in the interior of British Columbia by the Douglas-fir beetle,Dendroctonus pseudotsugaeHopk., has necessitated studies on many phases of the beetles' biology and behaviour. Among these has been a study of the beetles' flight. Although this insect flies for only a few brief periods during its life, these periods are vital in terms of the extension and location of areas of infestation.