Adult horntails are large wasps with a hardened, spear-like and upcurved projection on the posterior (Fig. 61). Larvae infest wood in trees or parts of tress that are dead or badly weakened. Infested wood deteriorates rapidly. Clusters of larvae and larval tunnels frequently are encountered when dead or old trees are removed from the sugarbush and cut into firewood (Fig. 62).

The species most commonly found in sugar maple and other eastern hardwoods is called the pigeon tremex (Tremex columba). The reddish and black adults are 0.75 to 2.0 inches (20 to 50 mm) long and have large wings. The rear half of the female often is marked with yellowish spots and bands, and in addition to the short, up-curved dorsal spine the posterior has a long egg-laying device (ovipositor) (Fig. 61). Eggs are deposited in the wood and the white, cylindrical, grub-like larvae tunnel into the wood. The posterior of each larva also has a characteristic short, stiff, and dark-colored spine. Full-grown larvae are approximately the diameter of a pencil and 2.0 inches (5 cm) long.