Mud Dauber

This guy was sitting on the bush outside my window. I knew I'd seen one before and was almost positive it was fairly harmless.
It is a Black and Yellow Mud Dauber, so named because they make their nests out of mud. They are technically wasps, but are more related to bees than to vespid wasps (the typical black and yellow wasp). They can be found from Canada to Central America, and they don't sting unless highly provoked - they don't even really defend their nests.
You can frequently find them on plants as the adult Mud Dauber feeds on nectar, but sometimes you see them carrying spiders and that is the food for their larva. They are great spider killers and this particular kind is very fond of jumping and orb spiders. Their cousins the Blue Mud Dauber is a primary predator of Black Widows, so go mud daubers!
The Black and Yellow is usually around an inch long and primarily black with a splotch of yellow on the back of the thorax and mostly yellow front two sets of legs (with some yellow here and there varying by creature). It has three pairs of legs with the back pair being very long. They also have one pair of amber wings that that cross one on top of the other above the abdomen. The most notable thing about a Black and Yellow Mud Dauber is it's long thread-like waist, it's about a 1/4 to a 1/3 of the entire body length!

The waist is a definite give away for this mostly harmless wasp.