Ctenocephalides canis /Siphonaptera ("wingless sucker")
It is amazing how miserable something so small can make a dog feel. My parents' dog was plagued by these little critters just a couple of days after having a bath. They can live in the soil, so just one trip outside can re-infest an animal. The hind legs of a flea are incredibly powerful, allowing them to jump long distances. There are many species of fleas, each one being attracted to certain animals. However, a dog flea will happily eat human blood if necessary. A friend of mine once rescued an orphaned baby squirrel. I went to her house to see it and soon had small black specks on my ankles! Fleas are adapted to survive in their specific habitat by being flat-bodied and having stiff hairs, making them hard to dislodge when their unwilling host tries to nip at them.