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Thread and PSA about Houdini flies (Cacoxenus indagator) for folks with bee hotels. When I first saw one at my bee hotel in 2019 I thought it was just a fruit fly from nearby compost pile. I was right about it being a drosophilid but very wrong about the "just". 1/11
It didn't behave like a typical fruit fly. Seemed unusually interested in bee tunnels and wasn't easily spooked by my camera. I ID'd it in 10 seconds by Googling, "small fly lurking solitary bee", which delivered this page by @Ed_P_Wildlife: https://www.edphillipswildlife.com/solitary-bees-and-parasitic-flies. 2/11
After identifying the fly I went to @BugGuidenet (as one does) to learn more. It turned out that there was only one sighting in the United States, in Brooklyn, NY, from 2011. Also at a bee hotel. At the time, I just thought, "rare fly — cool". https://bugguide.net/node/view/627975 3/11
But apparently it is not rare at all. @WSDAgov, for example, recently sent out an alert that the Houdini fly is established in Washington. The alert has helpful tips and links, too. https://agr.wa.gov/departments/insects-pests-and-weeds/insects/apiary-pollinators/pollinator-health/houdini-fly 4/11
If the Houdini fly is in New York, Pennsylvania, and Washington, it's likely in other places, too. If you see one, take a photograph and submit to @inaturalist so that experts can benefit from improved range data. Currently there's just one (mine). https://www.inaturalist.org/observations?verifiable=true&taxon_id=505829&place_id=97394&preferred_place_id=97394&locale=en 5/11
As a practical matter, the presence of the Houdini fly in the United States is yet another reason to move to nesting tubes that can be taken apart and purged of pests. @entobarbie has a good thread on this: https://twitter.com/entobarbie/status/1245089942382022656?s=20. 6/11
Sadly, many of my bees from 2019 season are inside unlined holes drilled in wood. I'm guessing hundreds of Houdini flies are going to emerge. Here's a photograph of my emergence box (bees exit via holes). I should have taken apart the paper straws during the winter (my bad). 7/11
Here is my 2020 hotel (or at least the backyard one). All of the holes are lined with paper tubes so I'll be able to purge Houdini flies. There are several companies that sell these inserts, plus trays that accommodate them (i.e., you don't need drilled blocks like I have). 8/11
If you'd like more information on the Houdini fly, I highly recommend this article by @m_c_marshall. Has a good description on how adults can inflate heads to break out of their mud cells. https://www.newscientist.com/article/dn19764-zoologger-houdini-fly-inflates-head-to-break-walls/ 9/11
@N_Nature also has several good videos of Houdini flies in action. E.g., https://nurturing-nature.co.uk/wildlife-garden-videos/the-houdini-fly-cacoxenus-indagator-escape-artist-that-uses-its-head-2/ 10/11
In case of interest, cacoxenus apparently means "bad guest". And I wonder whether indagator might refer to the the species' fondness for investigating holes in search of victims. #etymology #entomology https://www.merriam-webster.com/dictionary/indagate 11/11
