Nycteribiidae is a family of flies that are parasitic and have no wings. It's a surprisingly common condition with flies, which have an awful lot of parasitic and parasitoid species. They're crazy fast too and their resemblance to spiders is uncanny. They live on bats (and they're far from the only insect parasites on them) and that's all that they do. They've even got patches of hairs that work like velcro, making them absurdly difficult to pull off of the poor little chiroptera.
