The frame is white - they appear to be attracted to bright colors, the brighter it is, the more they flock to it.
You can't step outside wearing a white shirt without them "attacking" you, even if you don't go anywhere near the pool..
So anyway - we had this same problem last year, and we never could figure out what they are, OR how to prevent them.
We've added top quality chlorine & algecide (from a pool shop, not the diluted crap Walmart sells) - but that only kills the ones that are already there..
20 minutes later there is a whole new group of them..
What are they, and how can I kill AND prevent them from coming back??
Please help, these little *******s are driving me INSANE!!!! lol