In a previous article, we addressed differences between the cicada killer wasp and the Asian giant hornet (also known by its media-popularized name of ‘murder hornet’). Another insect that has been mistaken for the Asian giant hornet is the horntail wasp (Figure 1). Horntails, also called wood wasps, are wood-boring insects that are harmless to humans as they do not have venom and cannot sting. They get their name from the modification of their last abdominal segment, which projects outward like a horn or spike.
Adult horntails vary in size depending on the species, but most are anywhere from 1 to 2 inches long. Coloration also varies and is often a combination of black, yellow, brown, or blue. As mentioned, horntails get their name from the short projection (horn) on the end of the abdomen. This characteristic is present on both male and female horntails. The females will also have an ovipositor which is located beneath the abdomen.
Adult female horntails lay their eggs in wood, primarily that of dead or recently fallen trees. Upon hatching, horntail larvae tunnel and feed on the wood, slowly developing for about 2 to 3 years. Once they become adults, horntails chew their way out through small ¼ of an inch holes. Horntails are mostly found around maples, cottonwoods, and elms along with return burn areas of pine forest. Their activity may cause weaknesses in dead or dying trees, making them more susceptible to wind breakage.
In some instances, horntails have been known to emerge from freshly milled lumber if it was cut from an infested log. However, they do not infest lumber after it has been milled, so there is no threat to homes or other wood structures following initial construction. Aside from this uncommon issue, horntails are rarely a concern in South Dakota and management is often impractical and unnecessary.