|scientific name Scolytus tsugae |
common name Hemlock engraver.
Adults may be found most commonly around and on host trees while larvae are always found in tree trunks in galleries (Bright 1976).
Adult S. tsugae may usually present from May to early September, with peak activity late June and July (McMullen & Atkins 1959, Bright 1976).
The adults of these beetles may be 2.8 to 3.5 m long, with a black body (Bright 1976). In males, the frons is generally flat or slightly convex with course articulation. Females, on the other hand, have frons that is convex with finer articulation (Bright 1976).
This species of bark beetles overwinter as larvae (specifically as forth instars) (Bright 1976, McMullen & Atkins 1959). Pupation occurs in the spring in the bark of host trees and adults usually emerge in June and July (Bright 1976, McMullen & Atkins 1959). Egg galleries and oviposition occurs in June and eggs will hatch within 9 to 12 days (McMullen & Atkins 1959). There is only one generation per year (Bright 1976).
These beetles tend to infect mostly hemlocks (Tsuga spp.). They may also target firs (Abies spp.) and Douglas-fir (Pseudotsuga menziusii). They feed mostly on dying branches and twigs on the ground around host trees. Larvae feed on the wood of trees (Bright 1976).
These beetles may be found along the western coast of Canada and Rocky Mountain region in Canada (McMullen & Atkins 1959). They may also be found in western U.S.A. (Bright 1976).
Beetles of this taxon were originally described as two distinct species by Swaine (in 1917), as S. tsugae and S. monticolae. However, due to the presence of several intermediate morphological forms of these two species, both taxons were synonymized as S. tsugae (McMullen & Atkins 1959).
Sarah Smith (2012-02-07)
This image is of a male Scolytus unispinosus LeConte rather than S. tsugae
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