What is a worm? According to Webster's Dictionary, worms are any of numerous, small, elongate and slender creeping or crawling animals, usually soft-bodied, naked and limbless, or nearly so.
So, those many-segmented creatures that we call earthworms fit the dictionary definition of worm. Some people call these worms fishing worms, in recognition of their widespread use as fish bait.
We also use the term worm for specific types of internal parasites of humans and other animals: for instance, a type of flatworm called tapeworm that spends most of its life in the intestines of the infected animal. There, it helps itself to the partially digested food of its unwilling host.
Another creature that gets tagged with the handle worm is the nematode. Nematodes are usually small and very similar in structure, but they live in a wide range of habitats. Many are parasites and live in plants and animals. Some nematodes, like the soybean cyst nematode, are major plant pests. Others cause human diseases, such as trichinosis, river blindness and elephantiasis. Heartworm of dogs is caused by nematodes.
The term worm is also used for some immature forms of insects. The caterpillars of butterflies and moths are called worms. There are cabbage worms, immatures of the white cabbage butterfly, that turn up in our gardens, feeding on cabbage, cauliflower, brussels sprouts or broccoli. Also, the earworms that, from time to time, are found feeding in the tips of the ears of sweet corn. The codling moth is a major pest of apples and is one of the insects that might be responsible for a "wormy" apple.
At least one moth worm is not a pest insect. The silkworm is well known as the source of the natural fiber silk. The worm produces silk as building material for the cocoon in which it will change into a moth. We humans have learned to unwind the strands of silk in the cocoons for our own use. We make fancy gowns and ties out of the fabric produced from this worm product.
According to the dictionary definition, the immature forms of flies also qualify to be called worms. But scientists generally refer to fly larvae as maggots. However, to most people, an apple with a maggot in it is still a "wormy" apple.
Because several types of animals have been called worms throughout history, it is not always clear what is meant when the term worm is used. For instance, the old proverb about endurance, "Even a worm will turn." Are we talking about earthworms here? Or nematodes or flatworms? Or might this old proverb be a reference to some form of insect? A cabbage worm, perhaps?
In his recent book, "The Botany of Desire," Michael Pollan states that relative to the landscape, "Chapman regarded as beneficent in every particular; in his eyes even the lowliest worm glowed with divine purpose." Could the worm be an earthworm or even an apple maggot? The latter would be appropriate, since the Chapman referenced is Johnny Appleseed.
In the Bible, the term worm is used for fly maggots. Shakespeare also uses worm in the same fashion in his sonnets.
"Shall worms, inheritors of this excess,
Eat up thy charge? Is this thy body's end?" (Sonnet 146)
"So then thou hast but lost the dregs of life,
The prey of worms, my body being dead,
The coward conquest of a wretch's knife," (Sonnet 74)
The same usage is found in the children's song that includes, "the worms crawl in, the worms crawl out, the worms play peek-a-boo on your snout." Yes, folks, these worms are fly maggots. It does seem that, in the end, the insect worms have the last laugh.