"The study of natural history in the leisure of my life, since I was 14 years of age, has been to me a constant source of happiness; and my experience of it is such that independently of its higher merits, I warmly recommend it as a pastime, than which, I believe, no other can excel it". …Joseph Leidy (1823-91)

Joseph Leidy was Professor of Paleontology at the University of Pennsylvania for several decades in the 19th Century, and was the first person to discover dinosaur fossils in America. But he did not limit himself to the study of fossils; in fact, a biographer described him as "the last man who knew everything." He wrote articles about all kinds of animals, from microscopic amebas to dire wolves. He was especially interested in parasites, and illustrated them with intricate drawings that are marvels of precise observation. I first became aware of him early in my career because he discovered, named and illustrated many of the animals I taught about in my own courses. As I reflect back on my own career, I find the quotation cited above, despite its convoluted syntax, expresses my own feelings exactly.

Biologists are surely the luckiest people in the world; more than any other group of people, we are blessed with a variety of things to occupy our interest. Ostensibly, we study the plants and animals around us because they are important in agriculture, medicine and economics; but beyond that, these living things can be beautiful beyond description, and they challenge our minds with lives and behaviors that are often more intricate and bizarre than anything fiction can conceive. And best of all, these things are all around us.

After church on a recent Sunday, I was approached by a young man who hesitantly asked if I could answer a question for him. He had found a strange worm swimming in a discarded flower pot in his yard after a rain, and wanted to know what it was. It was about six inches long, very slender with no discernable difference between head and tail; and it swam clumsily by lashing about, frequently twisting its body into knots. From his description I recognized it as a horsehair worm. These worms are fairly common, although nowadays most people have never seen them. When they do show up, they are in places like birdbaths, pets' water dishes, or buckets that have been left out in the yard. Various species of them are found all over the world; and several of the American species were named by Joseph Leidy.

I remember finding a horsehair worm in the basin under the pump in my grandmother's yard when I was a small child. In those days everyone had seen horsehair worms in the rain barrels that were used to collect rainwater off the roof of the house for washing, and when I asked Grandma what it was, she knew immediately. She said it was formed by a hair from a horse's tail that had come to life when it dropped into the water. This puzzled me because we had no horses at that time, but Grandma said a bird had probably carried a hair from another farm and dropped it there. She saw nothing unusual about this; after all, in 1866 when she was born, most country folk still believed in Spontaneous Generation, the theory that lower animals were formed from non-living material. Years later, when I went to college I learned that Dr. Leidy was one of the scientists who proved spontaneous generation did not occur. I also learned about horsehair worms and the legend that gave them their name.

The legend held that sometime in the Fourth Century B.C. King Gordius of Phrygia created a very complex knot which he used to tie a chariot to a post in the town square. The strands of the knot were interwoven in such a way that the ends of the rope were hidden from sight inside the knot. It became known as the Gordian Knot, and local oracles declared that whoever untied it would become the next ruler of Phrygia. No one could figure out how to untie it until Alexander the Great invaded the area. He examined the knot and simply cut it in half with his sword. In one stroke he solved the puzzle, fulfilled the oracles' prediction, and provided us with a classic metaphor; 2,300 years later, we still refer to the solving of a tough problem as "cutting the Gordian Knot."

Horsehair worms typically twist themselves into knots when swimming, so they were given the name, Gordius, by the first biologists to describe them. Their lives are nearly as complex as the knot for which they are named. Dr. Leidy found that a worm six inches long laid a string of eggs that was over three times its body length and contained six million eggs. The eggs hatch into microscopic larval worms that become parasites in the bodies of insects such as grasshoppers or crickets. I used to give my zoology students grasshoppers to dissect, and it was not unusual for someone in the class to find one whose entire abdomen was filled by a horsehair worm; the worm would be folded and twisted into a complex knot in order to pack its six-inch body into that cramped space. As the worms grow, the infected grasshoppers weaken and become thirsty; they seek water and eventually die. The horsehair worms then work their way out of the bodies of their dead hosts and return to the water to mate and lay their eggs.

When we see wildlife programs on television, we are tempted to think all of the really interesting creatures in the world live in some exotic place like a rain forest or the arctic tundra. This can lead us to disparage the places where we live. The horsehair worm can help us to counteract this view; it reminds us that we don't have to be a Joseph Leidy to enjoy the natural world. Even in Emmitsburg there are strange and wonderful things to be seen. All we have to do is look.