Puddle problem
This puddle on the roof of a building is the result of a clogged drain. My job requires me to be strangely obsessive about standing water. I'm sure you can guess why.
Hey look at all the neat little wormy guys swimming in there! Surely they can't be a problem.
They can be when they come to the top of the water and split open and a mosquito crawls out of it.
On a positive note, I hadn't seen this happening in person before. Fascinating, problematic nature!
Hopefully this nearby European paper wasp will collect some mosquitoes to feed to her grubsisters.