I saw something totally crazy amazing yesterday. I went to check on my mason bee observation hive, and as I walked up I startled two insects of some sort that were investigating the tubes. I stood and waited and sure enough they returned, and when I saw them, I was pretty sure at once they were some sort of parasitic wasp here to investigate the nests. They were black and yellow, very smooth with no hairs, and they had these strangely rounded abdomens. One was larger than the other, so I wasn't sure one of them wasn't a male at first, but further inspection showed they both had ovipositors (egg-laying structures), and on their backs no less! I was curious what they'd do to try and access the mason nest, so I stood and watched them for a while. They sniffed all around with their antennae, in the tubes as far as they could walk, on the back, on the roof, even on the glass when I had the observation door open. The smaller one particularly seemed more interested in an old leafcutter nest from last year that didn't hatch for some reason. She sniffed all around the entrance and then stood their pumping her abdomen up and down. Then, to my extreme surprise, she ratcheted open her abdomen
roughly between her 3rd and 4th segments, revealing a strange clear membrane between the segments. Unfortunately, before anything else could happen, the larger female walked by and startled her, and the smaller one flew away. Thankfully, I had gotten a picture before she left, which turned out spectacular. Upon researching, I found the species is Leucospis affinis, and as I suspected, they are an ectoparasite of Osmia (mason bees) and Megachilidae (leafcutters). I also found a phenomenal HD video of a wasp in the same genus performing the same behavior as I saw in my wasp, showing that what I thought was her ovipositor on her back was actually her ovipositor sheath. Her ovipositor is actually attached underneath her abdomen near her waist and wraps all the way around onto her back, where it is protected in the sheath. In order to position this extremely long appendage between her legs so she can drill into the bee nest, she has essentially an extra joint in her abdomen, so she can open it almost to a right angle! How insane is that?!!
Here's the video that I mentioned. The poster doesn't allow it to be embedded here, but if you click on it, you can watch it.
