Unidentified Potter Wasp in a nesting tube

There were two species of wasp that nested in our mason bee house. I described the Black and White Potter Wasp in a previous post. This second wasp is smaller and not so boldly marked. So far, I have not been able to identify it. If any of you have any ideas what it might be, I would appreciate hearing from you.

This smaller wasp has a different behavior pattern from the Black and White one. One of the wasps, which seems to be the male, remains in the nesting tube, while the other member of the pair forages for mud to construct the nest and caterpillars to stock it. The photograph above shows the male on station in the nesting tube. It was quite bold, and was frequently seen to drive off the much larger Black and White Potter Wasps and prevent them form entering its nesting tube.

Left: A female wasp approaches the nesting tube Right: The male wasp attempts to mate with the female

However, this male had more on its mind than merely guarding the nesting tube. It was waiting for a female to return. Then, as the female was trying to enter the tube, the male would climb out and attempt to mate with the female. The photograph on the left shows a female approaching the nesting tube with a ball of mud. The photograph on the right shows how the male has climbed out of the nesting tube and onto the back of the female where it is attempting to mate. In this case, the female is carrying a small green caterpillar.

I have embedded a video below which shows the male wasp trying to mate with a returning female. Remember, if you get these posts by email, you may have to go to the blog at gkochert.com to see the video. Or you can go directly to Youtube and view the video at http://youtu.be/w7wa_AcqXmM