What is the source of these stains?

Just to be fair- this is in South Africa. I got it first guess, so its not that difficult.

spiderman ?

Bat guano?

Kamikazee skeeter full of blood?

What Jeffrey said.

Bingo!

Those are all here in Cuernavaca. I call them Malditos Vampritos. The ones with two humps suck more blood than the ones with only one hump. They’re so brutal that if you try to kill them with a fly swatter they rip it out of your hands and hit you with it. To kill them they make these special electric tennis racquets with steel strings. Here’s mine…

are You sure it wasn’t spiderman ?