Fleas can jump 30,000 times in a row without stopping, and they
are able to accelerate through the air at an incredibly high rate—a rate which is over ten times what
humans can withstand in an airplane.
Fleas have very long rear legs with huge thigh muscles and multiple joints. When they get ready
to jump, they fold their long legs up and crouch like a runner on a starting block. Several of their joints
contain a protein called resilin, which helps catapult fleas into the air as they jump, similar to the way a
rubber band provides momentum to a slingshot. Outward facing claws on the bottom of their legs grip
anything they touch when they land.
The adult female flea mates after her first blood meal and begins producing eggs in just 1 to 2
days. One flea can lay up to 50 eggs in one day and over 2,000 in her lifetime. Flea eggs can be seen
with the naked eye, but they are about the size of a grain of salt. Shortly after being laid, the eggs begin
to transform into cocoons. In the cocoon state, fleas are fully developed adults, and will hatch immediately
if conditions are favorable. It can be inferred that fleas will emerge from eggs as adults
$\begin{array}{1 1}\text{when they outgrow the cocoon } \\\text{when they sense there is access to blood
}\\\text{when they sense there is access to blood } \\\text{if there is too much carbon dioxide in the cocoon } \end{array} $
