Gatineau Park, Quebec. There were many of these smallish, intriguing little insects around the area I visited today. Most of them were on the undersides of milkweed plants. This one looks like a female, judging from the enlarged abdomen. They are superb mimics of paper wasps (Polistes), but look also like a bizarre cross between a wasp and a praying mantis!

Mantisflies are not flies, but belong to the Neuroptera group, the nerve-winged insects, which also includes Lacewings and Antlions.