My Dog Has Fleas, Also My Cat, My Bird, My…

These tiny prehistoric parasites have evolved a bold array of weapons, the better to torture their hosts

Though we spend a billion dollars a year to rid our pets of fleas, today's humans are not the meal of choice of the little vampires. Fleas, however, were constant companions of our forefathers. The highborn as well as the low clawed and scratched so much that rules of flea-picking etiquette were developed, women wore ivory flea traps and poets penned romantic verses about the intimate moocher. Because fleas can start epidemics, most notably bubonic plague, scientists have endeavored to learn the many extraordinary details about the flea's way of life, such as: fleas have evolved a specialized array of bristles and spines to hang on to their hosts; they can leap up to 10 inches over and over again and copulation can last up to nine hours.

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