Flea

All fleas are obligatory parasites of vertebrates. We can find them not only in humans but also in other species of mammals and even birds. They are superbly adapted to live in fur or feathers by having side to side strongly compressed body and possessing strong claws that help them to cling on a host despite his effort to remove them by scratching. Fleas do not have any wings and cannot survive long without its hosts, so they can be transferred only by more or less direct contact. They are important for humans not only as an occasional nuisance but more importantly as a vector of some serious diseases from other animals, like a plague. If we compare the physical abilities of fleas and humans, we are amazed. Flea of the size of a human could jump more than 100 meters high and if we load a wagon with 12.000 tongs it still would be able to push it!