Fleas are external parasites that feed on the blood of other animals. A flea circus was a sideshow attraction where real fleas were attached to items, such as tiny carts, making it appear as though they were trained to pull the cart.
Fleas are the insects forming the order Siphonaptera. They are wingless, with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood of mammals and birds. Some flea species include: Over 2,000 species have been described worldwide. Fleas are wingless insects (1/16 to 1/8-inch (1.5 to 3.3 mm) long) that are agile, usually dark colored (for example, the reddish-brown of the cat flea), with tube-like mouth-parts adapted to feeding on the blood of their hosts. Their legs are long, the hind pair well adapted for jumping: a flea can jump vertically up to 7 inches (18 cm) and horizontally up to 13 inches (33 cm), making the flea one of the best jumpers of all known animals (relative to body size), second only to the froghopper.
Contributions by Richard001, Ohnoitsjamie, and 18.104.22.168.