Horntail Identification


Though the Horntail (or Wood Wasp) looks like a wasp, it is not a wasp at all. It does not have a stinger, nor does it have venom. The long projection at the rear of its abdomen is an ovipositor (egg depositor). This is only seen in the female. On the top side of the abdomen, at its tip, is a triangular “horn” (best seen in a side view). This is what gives the Horntail its name. They are about one inch long with a cylindrical body. They are brown, black or metalic blue in color with yellow or red markings.

Horntails are attracted to dying, burned or recently cut wood. The female deposits her eggs into the wood of host trees, most commonly silver maple, ash, cottonwood, and elm. Along with the eggs, she deposits a fungus that will continue to degrade the already compromised wood. The eggs hatch in 3-4 weeks and the larvae begin consuming the fungus along with the wood. This may last anywhere from one to five years depending on the climate. The adult horntail chews through the last bit of wood and emerges, leaving a round exit hole 1/4″ to 1/2″ in diameter.

Even though horntails are completely harmless to humans, they often lay their eggs in recently cut wood. It is common for this wood to be milled with the wasp larvae already in it, allowing the larvae then to be built into a structure. Due to their large size, they are greatly feared by occupants of the structure in which they emerge as adults. They do not re-infest wood that is already built into homes. Extermination is an option, but it is not necessary. Please call our office for more information.