Biology.
Rudinsky and Zethner-Moller (1967) and Zethner-Moller and
Rudinsky (1967). The biology of this species on Douglas-fir in Oregon is as follows. Adults begin emerging in late March and continue through May; maximum emergence and flight are in late April and early May. The young adults feed on the small roots of dead, old Douglas-fir or the roots of young Douglas-fir, weakened after transplanting, before they actually invade the host. They are attracted to stumps,
freshly cut trees, and especially trees killed by the Douglas fir beetle. Whole oleoresin, -pinene, -pinene, and other components of resin have been shown to be attractive- Io H. nigrinu.r. Adults dig through the sawdust or soil around the host to reach the roots; they also enter at the base of the stem at the soil line.
Egg galleries are initiated by the females; the males enter later and copulation takes place within the gallery as well as outside. Egg galleries are long (about 9 cm) and winding, running parallel to the grain in one direction from the entrance hole. The part close to the entrance hole is almost always angled and wider than the rest ofthe gallery, and there are usually one or more branches and forked mines. Eggs are laid in distinct, evenly spaced niches about 1-1.5 mm apart. Where eggs are present, the gallery is packed with frass. From 20 to 40 eggs are laid per gallery; the maximum is about 63. There is no reemergence of parent adults. Larvae feed communally, forming no distinct larval galleries. Pupal chambers are found at all depths in the bark but mostly in the cambial layer. Adult beetles as well as full-grown larvae overwinter in the gallery. Most of the population completes develof,ment in I year, but some maylake 2 years. These overwinter as adults the second vear. Hylastes gracllls LeConte (nltldus Swaine)
Diagnosis. Length 3.44.3 mm. Reddish brown to black; frons with a median, transverse arcuate impression, densely
moderately broad
punctured; median carina extending from epistoma to transverse impression; pronotal surface with moderate-sized punctures, much finer and closer in front; elytral punctures moderate, smaller on sides and declivity; elytral interspaces finely rugose-punctate, uniserrately granulate on declivity; last abdominal sternite (C) distinctly grooved, with the setae more numerous and longerthan
on other sternites.
Hosts.
Pinus spp.:rarely Abies spp.
Distribution (Map l9). Southern British Columbia; western United States.
Biology.
Notinvestigated.
Hylastes longicollis Swai ne
Diagnosis. Length 3.4-4.0 mm. Reddish brown; almost identical with H. gracilis except pronotum more elongate, distinctly narrower than elytra;
strialpuncturescoarserthanin H.gracilis; pubescencelongerthanin H.gracilis. 52