Continuing Education and
Communication Services
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
12/24/01
Contacts:
Donald Lewis, Extension Entomology, (515) 294-1101, drlewis@iastate.edu
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
Yard and Garden Column for the Week Beginning Dec. 28
Insect Bragging Rights
By Donald R. Lewis
Extension Entomologist
Iowa State University Extension
Our national pastime of arguing about the biggest, the fastest or the best of anything and everything even extends to insects. Granted, the number of people arguing over insect record holders is relatively small compared to, say, the number of people with an opinion about the outcome of the Super Bowl. However, for the interested few, debates over the largest, fastest, oldest and loudest insects can be just as spirited as discussions about athletic competition.
Fortunately for entomologists, we have a referee to settle our disputes on insect records. The self-appointed judge of all insects great and small is "The University of Florida Book of Insect Records" (http://ufbir.ifas.ufl.edu). Since 1994, Thomas J. Walker, entomology professor emeritus, has edited this fascinating collection of essays written by University of Florida graduate students and others. The insect record book is not as popular or well known as that other record book published by Guinness, but it is just as much fun. At least for me.
How large is large?
Setting any world record depends on establishing appropriate criteria. So it is with picking the biggest insect. Can an insect be the biggest if it is long but not very big around (e.g., tropical walking sticks over 14 inches long)? What about insects that are long and wide but not very thick (e.g., moths with wingspans as great as 12 inches)?
It turns out that entomologists have been arguing about this question for centuries and publishing opinions since at least 1874. Not everyone agrees on how to measure or weigh an insect to declare a winner. But then not everyone agrees on how to score a triple Axel/ triple toe loop combination either.
The insect record book tries to resolve the question by settling on the criterion of "measurable bulk." This estimate of total volume is determined by length-to-width-to-thickness measurements.
And the world record holder is . . . . . a five-way tie for first place. It turns out there is no clear winner in the biggest insect competition, at least based on the objective data available. Don't let that stop you from cheering for a personal favorite, though.
Here are the five co-winners, and their clever scientific names followed by their length and place of origin. Note, with obvious disappointment, that none of these insects is from Iowa or anywhere near the upper Midwest.
South American Longhorn Beetle, Titanus giganteus; 6.5 inches;
French Guiana and Brazil.
Acteon Beetle, Megasoma actaeon; 5.3 inches; Columbia, Ecuador,
Peru, Brazil
Elephant Beetle, Megasoma elephas; 5.4 inches; Mexico through Venezuela
Royal Goliath Beetle, Goliathus regius; 4.3 inches; Ghana, Ivory
Coast
Goliath Beetle, Goliathus goliatus; 4.3 inches; Equatorial Africa
Biggest in Iowa
Unfortunately, no truly large insects make their home here in the alternately dry and frigid environs of the upper Midwest. On a good day we might find a 1.75-inch cockroach (none the size of dinner plates, as alleged). Larger still is the appropriately named giant water bug that lives in rivers and eats aquatic insects and small fish. This brown bug is shaped like a racing boat and is rarely noticed except for the occasional renegade that leaves the river for the bright lights of the auto dealership parking lot. Giant water bugs may reach 2.5 inches in length and almost 1 inch in width, but they are very flat.
Another large-looking, river insect is the dobsonfly. These critters look positively prehistoric with their big heads and long slender mandibles. Unfortunately for them (in the big bug contest), much of the 3-inch length is made of wings that conceal a rather unimpressive abdomen underneath.
Speaking of prehistoric appearances, the gangly praying mantis is around in southern Iowa, but only an occasional visitor to the center of the state. This is another example of a long insect (up to 4 inches) lacking in "measurable bulk."
Our largest moths are the cecropia moth and the polyphemus moth. Both have wingspans of 5.5 to 6 inches.
And finally, our largest beetles are wood borers found in dead trees. The largest (in my humble opinion) is the cottonwood borer occasionally found in southwest Iowa. This shiny black-and-white beetle lives in dying cottonwood and poplar trees as a larva, but emerges as a beetle up to 1.6 inches long and as big around as my little finger.
For the rest of the state, the beetle with the most bulk is likely to be the spotted grapevine beetle or the hermit flower beetle. Both live in rotten wood as larvae and then emerge in mid-summer as oversized June bugs at least 1 inch long and 0.5 inch in width and height.
Keep your eyes open out there next summer. Let us know if you spot a new record holder!
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ml: isugarden
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