Being enjoyably masturbated by common houseflies is something I discovered quite by accident at an early age.
While taking a tub bath at around the age of 13 or so I was annoyed by a housefly that kept buzzing around my head. I finally made a swipe at it with my hand and caught it in my fist. I didn't want to crush it in my hand, but I didn't want to release it so it could annoy me further, so I opened a small crack between my thumb and fingers and when it tried to escape I grabbed it between the thumb and forefinger of my other hand. I decided to tear one of its wings off so it couldn't fly. When I did, the fly wiggled out of my grasp and landed in the tub water which was of a depth that the head of my cock floated like a tiny island on the surface.
The fly landed near my cock and scooted across the surface to it and climbed aboard and began walking around on the head of my cock. Around and around it went creating quite a pleasurable sensation in my cock which responded by becoming erect, hard, and even more erect and harder the longer the fly walked on it and up and down its shaft. The fly didn't create sensations when it was on the shaft such as it did when in was on the head of my cock, so I ran more water into the tub so as to keep only the head of my cock above water, thus trapping the fly there.
Then I just lay back, relaxed, and enjoyed having the fly masturbate me for several glorious minutes until I experienced a volcanic ejaculation such as I had never had before.
After that I would intentionally catch a fly whenever I wanted to be totally pleasured while taking a bath. Some of those times I would shoot my load just as a fly was positioned right over the hole in my cock head and sent it on a ride on top of my hot cum. Timing that just right was a bit tricky, but a challenge and tons of fun when I succeeded.
I don't know if females could enjoy what I do, but it might be fun for them to try it.
I'd appreciate seeing comments from anyone else who has enjoyed this, or just general comments from anyone who reads this.