Sand fleas are all over beaches in South America, Africa, and various tropical islands. The little shits wait for you to roll up with your beach gear, and then they hop on your foot and just dig right in like a grave robber looking for Grandma's brooch. They'll suck your blood over several weeks as they bloat to a few times their normal size, all in preparation for the eggs that they're laying right in the buffet that is your foot. Gross. Slightly erotic, but gross.
The problem with sand fleas, aside from the obvious, is that they spread disease. They can cause something called tungiasis, which can lead to painful, deformed feet. And since the only way to get rid of the fleas is to dig them out, you risk some kind of secondary infection, like tetanus or foot holes (which isn't a disease as much as it's just holes in your damn foot). You don't want that shit.
Lucky for sand flea victims, a PhD med student happened to be studying the fleas in Madagascar when she got infected herself. Rather than treat it or just cry a lot and drink herself to sleep like I would, she decided to foster the little monsters. Up to that point, the life cycle of the flea was pretty unclear. Were they pregnant before they latched on, or did they get pregnant by using a person's foot as a brothel and boning deep inside? Just so deep inside that foot of yours. Oooooh.
This particular flea in this particular foot managed to outlast a typical infection and never laid any eggs, leading the researcher to believe it had never been fertilized. This means that they normally do have that dirty foot sex, and this one missed the boat because it was being so closely monitored. Knowing when and how sand fleas get their hump on means knowing more about the disease you're trying to prevent in places where infection rates reach as high as 50 percent, meaning literally half of everyone who may go near sand in some of these countries is getting infected. All because sand fleas like doin' it on us more than anything. That's fucked.