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Semi-aquatic ichneumonid? Possibly undescribed.

Hi everyone,

I recently (May 1 to be precise) went to Barton Creek Habitat Preserve in Austin, Texas as part of a vertebrate natural history class I was leading. One of the coolest things I saw, however, was an invertebrate, a wasp that was crawling around underwater. It looked like a female ichneumonid that was searching for hosts. It was in very shallow, fast-flowing water where there were many black fly larvae (along with a few pupae). There were also mayfly nymphs and Hydropsychid caddisfly larval nets.

I did not collect it or take any photos, but I did record a video with my phone (unfortunately you will have to click the gear at the bottom of the video and change it to HD to really see much):

The wasp was around 7-9 mm. After a little research, it may be in Ichneumonidae, subfamily Orthocentrinae if it was after the blackflies, since that was the only subfamily with hosts in Nematocera I was able to find. Regardless, it sounds like there is a lot of undescribed diversity in semi-aquatic ichneumons, so it could be new.

I ended up seeing two, but I wasn't able to spend much time since I was leading a class about vertebrates. I'm returning to the same spot this Thursday for another class, and I may try to collect one then if they are still around. I'm sure there's someone out there who can give some context to this observation.


I toned the video down to 144p and got excellent results. The default was 480p, and allowed too much flutter to view the video correctly. I commented on your YT page as well... Excellent work.

Great video documenting that behavior
Really interesting and pretty cool how the fly larvae were responding to the presence of the wasp.

I'd definitely try to collect one if you see it again. Bob Carlson, our ichneumonid expert, is on hiatus, but you might contact Andrew Bennett at Agriculture Canada, who lists aquatic Hymenoptera as an area of interest.

Our resident ichneumonid expert
When will Bob Carlson return for active duty?

No idea
I'd recommend sending an email to Dr. Bennett and see what he says about your observation.

I went back to the same site and saw at least 6 more of them. I got more video, photos, and a specimen as well; found in this post:

I'll email Dr. Bennett as well. Cheers!

Another person you might try
is Gavin Broad. I'll be interested to know if Dr. Bennett is responsive; I'm on the lookout for a new person to send reared ichneumonids, since Bob seems to be quitting for good.

Thanks for the info!


I sent the specimen to Dr. Andrew Bennet at The Canadian National Collection of Insects. He says that it is surely in genus Tanychela, and perhaps Tanychela pilosa (Dasch). It differs from all known specimens of that species, however, in the coloration of the front femur, so it may still be something new. The specimen will stay at the CNCI, so maybe one day someone will use it for genetic analysis. Cheers!

So it may indeed be a new species! And it's also BugGuide's first photos of the genus! Nicely done.