JANUARY
2001

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

01-25-01

Acrobatic Blood Suckers of the Insect World

They are hard-bodied wingless, blood sucking insects with extraordinary powers of leaping-that's how Webster's New Collegiate dictionary describes fleas.

Most of us recognize fleas when we see them. They, along with flies, are probably the two insects that most people can positively identify.

Webster's dictionary also states that fleas belong to the insect order Siphonaptera. The order name is very descriptive. Siphon refers to the sucking-type mouthparts that are used to extract blood from mammals or birds. Ptera is the Latin term for wings, and the "a" preceding it means without. So the name indicates wingless; thus, fleas are wingless, blood suckers!

But most of us already know that, and it is precisely why we don't like fleas. Even when we catch fleas, they are hard to kill. That's because they are hard bodied. Their very tough exoskeleton protects them from the claws and teeth of the animal hosts that try to destroy these little parasites.

The lack of wings also benefits fleas by allowing them to move freely among the hairs of their hosts. Wings would just get in the way in such an environment. Living on hairy animals also means that the tall, skinny structure of the body is a benefit. Their narrowness allows them to fit nicely between hairs as they run along the back or belly of the host.

Another structural characteristic of fleas is that they can jump. Boy, can they jump! Their hind pair of legs is modified for jumping. Heavy muscles and a protein that is elastic, called resilin, allow fleas to jump great distances-at least for such small insects. Fleas have been known to jump up to 12 inches.

A flea jump is not just a feat of extraordinary elastic and raw power. It is also a work of acrobatic grace. When a flea jumps, it also does a back flip-landing on its legs ready to spring again to elude any would-be flea killer.

There are many types of fleas in the world. Scientists have identified about 1,900 species. Many have common names that reflect some host animals, but the names are somewhat deceiving. For example, there are cat fleas, dog fleas, human fleas and rat fleas. However, these fleas do not necessarily occur on their namesakes. The most common flea found on dogs is the cat flea-a fact that no doubt adds insult to injury for dog owners who are not fond of cats. The human flea feeds on all kinds of animals, including rats, pigs, anteaters and ducks. 

The rat flea is well known as the insect that transmitted the bacterium Yersinia pestis that causes bubonic plague. This flea was happy to feed on rats and then humans, acting as a courier for the disease organism in the process. Today, the disease exists in the United States in populations of rodents, such as squirrels and prairie dogs, which are suitable feeding hosts for the rat flea.

While we all know the adult flea, the immature form is less well known. That is because the baby fleas live and feed in the nest of the host. These young fleas feed on debris in the nest, including hair, flakes of skin and the droppings of the adult fleas.

When the immature forms complete their feeding, like many other insects they pupate. The pupae have an unusual habit of remaining in that stage until dinner is served for the adult. The adult does not emerge from the pupa until a host animal returns to the nest. In fact, it is the vibrations associated with the footfalls of the host returning to the nest that signal that the adults should emerge.

Fleas are remarkable little creatures unless they are feeding on you or your dog. Then our attitude changes. As William Shakespeare wrote, "That's a valiant flea that dare eat his breakfast on the lip of a lion!"

 

Writer: Tom Turpin
Editor: Olivia Maddox