Pigeon Tremex Wasp

The Pigeon tremex, Tremex columba, is a species of horntail, native to Eastern and Western North America. The females are larger than the males, with females growing to 25-30mm in length, and males about 20-25mm. The larvae feed on dead and dying trees such as beech, elm, maple, and oak (Wikipedia). Both sexes have a wasplike horntail with abdomen ending in hornlike projection and females have an encasing ovipositor. Spotted this female on a sycamore leaf at Montezuma Castle National Monument, near Camp Verde, Arizona. It looks scary, but is harmless to humans.