Flea-flickers and football fields

Abstract

I don’t know who first came up with the idea of measuring lengths in units of football fields, but I imagine it was an entomologist. Football fields are the preferred units for expressing equivalent distances that insects, particularly fleas, could jump if they were the size of a man. No sexist intent, here; for some reason, these equivalencies always seem to be measured with men in mind. (My personal theory is that only a guy would care if he could outjump a flea if he were the same size as a flea.) Football fields are routinely used to illustrate the prodigious athletic capabilities of insects. According to the standard text for introductory entomology, Borror, DeLong, and Triplehorn (1981), “When it comes to jumping, many insects put our best Olympic athletes to shame; many grasshoppers can easily jump a distance of 1 meter, which would be comparable to a man broad-jumping the length of a football field.” Information in the 1990 Guinness Book of Records, proclaiming Pulex irritans the “champion jumper among fleas,” reported, “In one American experiment carried out in 1910 a specimen allowed to leap at will performed a long jump of 330 mm (13 in) and a high jump of 197 mm (7.75 in) (pg 41).” These statistics in turn inspired some calculations on the Bugman Bug Trivia website (http://www.bugs.org/BUGQuiz/answers/flea_answer.shtml): “So, let’s do the math... after scouring our extensive piles of resources, the best estimate of flea length we could find was 1/16 to 1/8 of an inch. So let’s take the large estimate (‘cause that’s more conservative). 1/8” is about 3 mm. So, a flea can jump about 110 times its length. Now, for example, if you are 5 feet tall (or long) and could jump 110 times your length, you could jump about 550 feet, which is about 183 yards or nearly 2 football fields!” I suppose these analogies are helpful to sports fans, but I have no clear concept of how long a football field is (having attending only one and a half football games in my entire life, both of which took place over thirty years ago). Moreover, “football field” as a unit means different things in different countries. As I understand it, Canadian football is played on a field that’s 110 yards long (which means that their football fields have been larger than U.S. fields for longer than their dollars have been). And “football” in Europe refers to soccer and I have no clue how long a European soccer field is, nor whether European fleas make the conversion. Admittedly, not all of the jump analogies revolve around football. Whereas football field units seem well suited to illustrate the length of a flea’s broad jump, they would seem far less useful to illustrate the relative height of a flea jump. Indeed, more often than not, jump-height equivalents are often measured in units of buildings, usually relatively famous ones. The utility of such comparisons depends on one’s familiarity with scenic landmarks; in an article about the Olympic prowess of animals, R. McNeill Alexander references the apparently popular comparison equating a flea’s 30-centimeter jump to “a man jumping over St. Paul’s Cathedral” (Milius 2008), which for American stay-at-homes is unenlightening at best. But the football field as a unit of measure is so firmly entrenched in the popular conscience that occasionally it serves as a unit of height—e.g., at “Super bugs? Whimpy [sic] humans?” (http://www.ftexploring. com/think/superbugs_p1.html). “Fleas can jump over 80 times their own height, the equivalent of a 6 foot tall human jumping over a building 480 feet (more than 1 and a half football fields) high!” But short of a seismic cataclysm, when can people see football fields stacked vertically? The problem with all of these calculations, of course, is that they fail to take into account the surface area/volume ratio. Small organisms, such as insects, live in a world dominated by surface forces. The bigger the organism, the greater is its volume (which is a function of length times width times height) relative to its surface area (which is a function of length times width). Cubic dimensions scale up faster than do squared dimensions, so, as organisms increase in size, This flea-flicking business has me running in circles... or is that jumping?! What was that play again?