Stinging freshwater Hydroids mussles and beetles

[BioDiver]

Yeah, those bugs can certainly give you quite a bite or even a poke. I believe those backswimmers like you posted actually have piercing mouthparts. Meaning they basically "spear" what they want to bite or eat and then "suck" out the insides. My guess is you ticked one off so he gave you a good stabbing.

I still can't find anything about stinging mussels though. Most early life-cycle mussels around here are a parasitic stage called glochidia. They attach to the gill filaments of fish and then later drop off as they mature. From there they are basically just smaller versions of adults. The glochidia would be much too small to sting and the young adults have all the same body parts as the adult mussels do, just smaller.

Let us know if you find anything popolarbear.