|scientific name Scolytus ventralis |
common name Fir engraver
Adults may be found on white firs (Abies concolor (Gord and Glend)), douglas-firs (Pseudotsuga spp.), spruce (Picea spp.), and hemlocks (Tsuga spp.). Larvae and pupae will be found in the trunk/bark of these trees.
Adult may be seen from June to September with peak activities in July and August (Bright 1976).
Adults are around 3.3 - 4.3mm in length (Bright 1976). The body is generally black or reddish brown. In both males and females, the second sternite is produced anteriorly (weaker in the females) and only the males have an acute tubercle on the posterior margin of the 2nd sternite (Bright 1976, LaBonte et. al. 2003).
Females will create galleries with help from the males and may lay from 57 to 260 eggs. Upon hatching, the larvae will feed on wood tissue, moving at right angles from the galleries. Developmental time of larvae will vary depending on environmental conditions. Typically, development will take a shorter time at low elevations or in warmer climates. Pupation often occurs in the bark (Bright 1976). Overwintering behavior may be carried out by both adults and larvae (Bright 1976). Depending on localities and conditions, number of generations produced in a single may vary. In extreme cases, a complete life cycle may require 2 years (Bright 1976).
Adults will generally attack an individual branch, causing death in said limb, but may also target any parts of the host trees (Bright 1976).
These beetles may be found in Alberta and British Columbia, as well as parts of western USA (Bright 1976).
It has also been noted that these beetles tend to colonize trees that are already suffering root-rot infections (possibly attracted to pheromones released by said trees) (Macias-Samano et. al. 1998). Furthermore, S. ventralis may carry the pathogenic fungi Trichosporium symbioticum Wright, which is essential in the beetle’s successful reproduction (Macias-Samano et. al. 1998, Ferrell et. al. 1993). As a result, heavy infestations may be fatal for particularly susceptible trees that are already suffering from other ailments. It has been suggested that the threats of S. ventralis outbreaks to firs may be predicted via observation of said trees defense response to artificially inoculated fungi (Ferrell et. al. 1993).
Comments are published according to our submission guidelines. The EH Strickland Entomological Museum does not necessarily endorse the views expressed.