This Is Not a Weasel: A Close Look at Nature's Most Confusing Terms

Natural History, March, 2004 by Laurence A. Marschall

by Philip B. Mortenson John Wiley & Sons, Inc., 2004; $16.95

Here is a reference book for those who can't tell an ass from a burro. The designation "ass," for Equus asinus, includes a large number of horselike breeds of mammal, from the striped-legged Somali wild ass to the domesticated ass, commonly called a donkey. Burro (originally the Spanish word for donkey) is simply American English for a donkey that lives in the western United States, Mexico, or Latin America. And "donkey," in turn, is a word that probably derives from the animal's Old English description as small and dun-colored. So though all burros are asses, not all asses are burros.

Philip B. Mortenson, who produced this useful and entertaining volume (his first published book, we are told), studied philosophy of science at the University of Minnesota, in Minneapolis, and he clearly had a lot of time on his hands after graduation. He has schooled himself in the intricacies of plant and animal taxonomy and digested a sizable library of lore on natural history (the dense bibliography at the back of the book goes on for seventeen pages). All this effort has not gone to waste, however; Mortenson has helped bring order to the jumbled world of biological nomenclature.

Consider how many everyday disputes grow out of a confusion of terms: Is the porpoise mistakenly netted in the same catch that provided the tuna for your lunchtime sandwich a fish or a mammal? Does the tomato on your tuna sandwich count as a fruit or a vegetable? Does the boss who scheduled your sadly abbreviated lunch break deserve to be called a weasel or a stoat? Mortenson's handy reference provides detailed and thoughtful answers, in chapters arranged roughly by taxonomic category.

Be cautioned, though: one can learn too much from a book like this, and newfound knowledge should be doled out sparingly. The host at a festive dinner might not be particularly gratified to learn that the candied yams he has just brought to the table are not yams at all but sweet potatoes, quite a different kind of plant. Sweet potatoes are true roots belonging to the morning-glory family, and they do not develop "eyes." Yams, like ordinary potatoes, are tubers, and they do. Sweet potatoes are sweet and small enough to fit in a baking dish. Many yams have a bitter taste that only boiling can dispel, and some species can grow as long as eight feet and weigh more than a hundred pounds. And whereas yams are important foods in the tropics and in Asia, they are seldom sold in North America, and almost never appear on dinner tables--especially the eight-foot-long variety.

You could easily suffer taxonomic overload if you read this book straight through--there's enough lore in the section "Caterpillar Grub Larva Maggot Nymph" alone to occupy an idle afternoon. And because the book is not illustrated, you may need a stack of field guides and illustrated encyclopedias close by. None of the entries is more than a few pages long, however, so true nature lovers may want to locate a copy in the bathroom, or wherever else the browsing opportunities are frequent but short.

Even with This Is Not a Weasel at hand, of course, clear distinctions may often be impossible. Unfortunately for taxonomy, nature does not readily shoehorn herself into mutually exclusive categories, and the subtle variety she offers up seems almost infinite. Moths are generally distinguished from butterflies by their drabness, yet the luna moth is almost flamboyant. Moths have antennae that don't look like the stalky antennae of butterflies--but there are exceptions. And though most butterflies have slender bodies, some are as pudgy as moths. So, is that a butterfly or a moth on the screen door? If it really matters, even Mortenson's book may not provide the definitive answer.