Hosts: Douglas-fir, pine and true fir
Carpenter ants are large in size, about 5-15 mm long, and
black or black and red in color. They tunnel in the wood of stumps,
logs, dead standing trees, the interior dead sections of livings
trees, and the wooden portions of buildings. These galleries are
honeycomb-like in appearance; the walls are sandpaper smooth, free
of frass, and run across the grain. The wood borings, which are
coarse and fibrous, are pushed out of the tunnels and may accumulate
at the base of inhabited trees.
Biology: Mating occurs during mass flights
in the spring. The female then lays eggs, which take approximately
2 months to become mature larvae. The larvae then pupate in cells.
Each individual will emerge as one of three possible castes: winged
males, winged females, or workers. Carpenter ants do not eat wood
but excavate galleries for nesting purposes. These insects are general
feeders, and will eat animal food (such as caterpillars, meat, or
refuse) and sweets (from aphid honeydew, ripe fruit, or sap.)
Effects: The excavations in wood can be
so extensive that the structural integrity of the tree is lost,
predisposing the tree to wind breakage.
Insects and Diseases: Horntails or “woodwasps”
(Siricidae) have similar excavations in host trees. The main differences
being that they actually have the wood borings pass through the
digestive tract and are packed in the tunnel behind the larva. They
usually attack fresh logs or newly dead trees. Adults are generally
thick-waist, wasp-like insects that are metallic blue or black in
color. Adults emerge in late spring or summer and lay eggs in solid
wood (conifers or hardwoods) and the life cycle can range from 1
to 2 years. Pupal cells are found in the phloem and the exit holes
from mature adults are round.