[This was written by Fran Siebrits and published online by Wild Magazine http://www.wildcard.co.za/, 2011]

Although regarded as a pest by most, and classified as an external parasite by scientists, fleas have some of the best legs in the animal kingdom. Their long, hind legs are perfectly adapted to catapult themselves into the air, making them extremely good jumpers… as we have all been witness to. But the mechanics behind these impressive jumps have only recently been explained.

Scientists have been doing research on fleas for decades. In 1967 already, a scientist discovered that fleas store the energy needed to jump in pads made from special elastic protein. There have since been many debates on how fleas harness this energy which allows for these massive leaps. Just over 40 years later, with the availability of the necessary technology, the mystery as to how fleas jump has finally been resolved.

The complicated leg of a flea is made up of the knee (trochanter), shin (tibia) and toe (tarsus). In a stationary position, fleas rest on the entire lower region of their legs, from knee to toe, hence the assumption that they push off with their knees. However, the latest research shows that fleas use their toes to propel themselves into the air, and not their knees.

Fleas push down through the shin onto the toes. They exert a force from the spring in their thorax through leg segments which act as a lever to push down on the toes. This adaptation makes it possible for fleas to jump at speeds as fast as 1.9 meters per second.

Further examination revealed specialised gripping claws on their shins and toes, allowing the flea to get a good grip to push off from. The knees, however, are completely smooth, lacking in claws and therefore preventing it from a successful take-off.

This may seem a bit trivial; does it really matter whether fleas push off from their knees or their toes? Well, after 44 years of debates and opposing views, in the scientific field it is an extremely big deal! It is because of such debates that we know now that the world is round, not flat. It is because of science that we know that excess sugar makes you fat, that moving electrons around in a specific way gives us electricity, and that smoking causes lung cancer. Once again thanks to science, you know something interesting about fleas to add to the next dinner conversation.

Flea Facts

• A flea can jump vertically to 18cm and horizontally to 33cm. That’s quite impressive for a wingless insect with a boy size roughly 200 times smaller.

• Second only to the froghopper, it is one of the best jumpers of all the animals (relative to body size).

• A female flea can lay 600 eggs in a lifetime, host dependent.

• Flea larvae are blind and go through three larval stages before becoming an adult – this process can take anything from a week to several months.

Science Daily [12 February 2011] http://www.sciencedaily.com/releases/2011/02/110210201005.htm
Wikipedia http://en.wikipedia.org/wiki/Flea