Field tests, using bolts of American elm trees either uninfested or infested with laboratory-reared or feral Hylurgopinus rufipes (Eichhoff), the native elm bark beetle, were conducted to evaluate colonization behavior of the beetle. The data confirm that (1) colonization of elm by H. rufipes can be accounted for by host attractants alone; (2) overwintered adult H. rufipes are attracted to broodwood (moribund or recently cut elm) in the spring, but summer-emergent adults are attracted to healthy elm; and (3) H. rufipes attacks broodwood primarily during evening beetle flights, and females initiate the gallery. A beetle-produced sex pheromone may be involved in the male–female pairing on broodwood.