Beetle species approaching 400,000
“There is a story, possibly apocryphal, of the distinguished British biologist, J.B.S. Haldane, who found himself in the company of a group of theologians. On being asked what one could conclude as to the nature of the Creator from a study of his creation, Haldane is said to have answered, “An inordinate fondness for beetles.” –G.E.H.
Sixty years ago this month, G. Evelyn Hutchinson essentially established the modern study of biodiversity in a short, supremely elegant paper titled, “Homage to Santa Rosalia or Why are There so Many Species of Animals?” The Haldane quote above was just an aside, a footnote at the bottom of the second page as G.E. was warming to his topic.
Why indeed are there so many animal species? Why are there so many more terrestrial animals than aquatic forms when the oceans occupy so much more of the planet? Why are there so many more animals than plant species? Why are there more species in the tropics than in temperate regions of the world? Why have some groups of organisms diversified into numerous species while others have seen little change over the same period of time?
And why are there so d— many beetles?
Thinking back to seventh-grade science with Mr. Connerton, similar species are grouped together in a Genus, similar genera in a Family and similar families in an Order. Beetles belong to the Order Coleoptera, a name derived from Aristotle’s term for beetles, koleopteros, meaning sheath-winged,
Almost all flying insects have two pairs of wings although in some groups only the front pair is used for flying (think flies and mosquitos) while in others it’s the back pair. When not flying, a beetle’s delicate hind wings are folded up and tucked under its hardened front wings like sheets in a linen closet.
Sometime when you get a chance, put a ladybug — biologists prefer to call them lady beetles since they aren’t bugs — on the back of your hand. Once it gets its bearings, it’ll rotate its rigid front wings (called elytra) out to the side, unfold its dark and much larger hind wings and flap away. (YouTube “Ladybug take off” to see it in slow motion.)
Haldane wasn’t kidding about the inordinate fondness thing. At present, the known number of beetles is approaching 400,000 species, with new (mostly tropical) forms being discovered each year. That amounts to some 40% of all insects and a quarter of all known animals. (A 2015 study using four separate methods to estimate the total number of the planet’s beetles came up with a range of 0.9-2.1 million species.)
Beetles are found in every habitat except the open sea and polar regions — basically wherever vegetation is found. While many are generalists in their diet, feeding on a wide variety of plant and animal material, others are highly specialized. The infamous boll weevil, for example, feeds exclusively on the young buds and bolls (fruits) of the cotton plant.
Unknown in the U.S. until 1892 when it was first seen near Brownsville Texas, by 1920 the beetle had reached and caused incalculable damage in all cotton-growing regions of the nation. But in 1978, the U.S. Department of Agriculture initiated the Boll Weevil Eradication Program with the lofty objective of eliminating the invasive species throughout the country. Incredibly, it did the job or nearly so. By 2012, the weevil had been eradicated from all but a few areas in southern Texas. Hailed as one of the world’s premier examples of Integrated Pest Management involving controlled applications of pesticides, modifications in agricultural practices, pheromone trapping and insect predators, the program has had an enormous impact.
Prior to 1978, up to 41% of all insecticides were directed toward efforts to control boll weevils. With the beetle under control, pesticide use has plummeted, cotton production has become more economically viable and non-target insect populations are recovering.
Colorado potato beetle, emerald ash borer, corn flea beetle, Japanese beetles, bean leaf beetles … Ohio has her share of problematic pest beetles to talk about. But let’s end with an appreciation of an emerald green to gun-metal blue killer you may have recently encountered on a sunlit forest path.
If the six-spotted tiger beetle’s iridescence doesn’t catch your eye, it’s jerky, stop and go running behavior might get your attention. Their overlapping white mandibles and disproportionately large eyes (the better to see you with, my dear) are further distinctive features of these ferocious predators of small arthropods.
There are several thousand species of tiger beetles around the world, most of which, in tiger-like fashion, run down their prey on the ground. The six-spotted will try to nip you if you’ve a notion to pick it up, but the bite doesn’t amount to much.
If you’re a person.
Ken Baker is a scientist and a retired biology professor. If you have a natural history topic you’d like the author to consider for an upcoming column, email your idea to firstname.lastname@example.org.