Rat fleas are parasites that feed on the blood of their rat host. They prefer warm environments to live in. They do have 2 eyes, but their eyes are only able to see light. Their mouth injects saliva in order for them to be able to draw blood in which to feed on. Fleas are able to jump 200 times their lengths and 130 times their height.
They start out as eggs that are laid on the ground or in the animals nesting site. The eggs resemble a tiny worm. These eggs, also known as larvae, feed on dead skin, animal hair, and the droppings of other fleas. They then reach the stage where they are ready to pupate. They pupate by spinning a silken cocoon in order to reach the stage of pupae. After they pupate, and they come out of their cocoon, they are able to reproduce, and they feed on blood.
These fleas are known to be transmitters of major diseases, some of which are deadly. Famously, they are known to be one of the major causes of bubonic plague outbreaks. They contract diseases by biting an infected rat and then transmit the disease to people when they bite them.