Sistentes
Guides
Adelges cooleyi
Cooley spruce gall adelgid, Douglas fir adelgid, gall adelgid
Adelges cooleyi is a gall-forming adelgid native to western North America, specifically the Rocky Mountains and Cascade Mountains. It is a host-alternating species with a complex life cycle involving two primary hosts: spruce (Picea) species as primary hosts and Douglas fir (Pseudotsuga menziesii) as the secondary host. On spruce, the adelgid induces the formation of distinctive pineapple-shaped galls at branch terminals. On Douglas fir, it produces white, cottony wax masses containing eggs but causes less conspicuous injury. The species has two generations per year and exhibits morphological dimorphism: progredientes migrate to current-year needles while sistentes settle on older needles.