We fleas bite animals for the same reason you bite candy bars
-- hunger. Adult fleas suck blood for food. The animals we suck
the blood from are called hosts. Most kinds of fleas suck the
blood of mammal hosts such as cats and dogs.
There are about 2000 different species (kinds) of fleas. Some
species, such as rabbit fleas, have only one kind of host. But
some species use many hosts. Cat fleas, for example, turn up on
cats, dogs, rats, squirrels, rabbits, chickens, and humans. Gotcha!
Fleas are the best little jumpers in the world. We have special
springy material in our legs that helps us take off faster than
any other animal. And we can jump really far -- 150 times our
length. That would be like an adult person jumping over 30 school
buses lined up end to end!
Good thing we're such good jumpers. We can't fly. And sometimes
we need to get away fast - like, if a dog is scratching at us.
Also, we need to be able to get onto our hosts. Most hosts are
fast movers. So we can jump and jump and jump, as much as 600
times an hour if we have to!
We fleas seem like little pests to you. But in the Middle Ages,
we were a very big deal. Partly because of us fleas, 25,000,000
people died. That was one out of every four people living in Europe
at the time! They died of the bubonic plague, a terrible sickness
caused by a bacteria. The bacteria were carried by rat fleas.
Adult fleas burrow through fur and feathers. We're built for
it, with pointed heads, flattened bodies, and no wings. We also
have combs and bristles on our bodies for clinging to our hosts'
body coverings. So it's really hard for the hosts to get us off.
My friends the rabbits fleas don't lay eggs until after they
suck blood from a pregnant rabbit. Then they lay eggs in the rabbit's
nest. The fleas' eggs hatch around a bunch of baby bunnies. So
the young fleas have a nest of new hoppers to hop onto.
We fleas lay lots of eggs. A female cat flea lays one egg an hour, every hour of the adult life (which is usually about three months). Most kinds of fleas don't lay their eggs on a host animal Instead, we lay them in the host's nest or den. That's what makes us fleas so hard to get rid of. You may get us off your dog or cat. But a new group of fleas is waiting in your pet's bed. They can wait a long time too. When a young flea grows up, it covers itself with a cocoon and waits -- for up to a year. When it finally senses an animal nearby, it breaks out of its cocoon and jumps on board.