Subject: biting swimmer in pool
Geographic location of the bug: Queen Creek, AZ
Time: 04:38 PM EDT
Your letter to the bugman: We have found this type of bug in our Arizona pool (more than once). It swims very fast, it is not a water boatman, the legs are different and all go the same direction. Also it swims belly down. It has 6 legs, 2 small antennae, and it appears to use a bubble on its underside to help it go up to the surface and down again. It also bites (or stings), and if a person is in the pool nearby, it will make a beeline for them. Very aggressive for a little creature. (the 3rd photo is not 2 bugs, but a reflection on the side of the glass it was in).
Nobody seems to be able to identify it. Thank you in advance for your help!
How you want your letter signed: Zonie Girl
Dear Zonie Girl,
Thank you for pointing out and for having documentary images showing the position of the legs while swimming. The is a Beetle, and based on information on BugGuide, including “Aquatic forms may superficially resemble Dysticidae but can be easily distinguished by antennae. Many have keeled sterna. The adults come up for air head first, and move hind legs alternately (Dysticidae come up for air tail first and move hind legs together, like oars)”, we conclude this is a Water Scavenger Beetle in the family Hydrophilidae. Though the bite might be an annoyance, we do not believe it poses any threat to humans.
Thank you for the quick response! I looked these up online, and yes, that is exactly what this bug is.