Last month while hiking through Sequoia National Forest at about 7,000 feet, I came across this impressive horntail (Urocerus californicus). There were large cut fir trees and pines about and I expect that it was attracted to these. Horntails are our largest insects in the suborder Symphyta (in the order Hymenoptera). Immature stages feed in rotting wood. This individual was over an inch and a half long (larger with legs and antennae extended).
Horntails are related to bees and wasps. They are not nearly as frequently seen as their more familiar relatives because they don’t visit picnic sites or pollinate flowers. That said, we have several species in the US. My compliments to Nathan Schiff et al. who just recently (last month in fact) published a beautifully illustrated guide to our fauna in the Canadian Journal of Arthropod Identification.