Bess Beetle Penny Pull

The bess beetle is the first live animal that St. Bernard’s boys work with in science labs.  Bess beetles are terrific little creatures that capture the imagination and attention of our boys during experiments throughout their first grade year--to be followed by the crayfish in second grade, the gerbils in third grade, and microscopic animals and plants in fourth grade.  The best bess beetle experiment of all is the penny pull.  (In fact, the Carolina Biological Supply Company breeds and sells bess beetles for this very experiment!)

Essentially, the bess beetle penny pull tests the strength of the animal’s exoskeleton.  During the process, the animal traverses a paper towel track pulling a sled (petrie dish) by a taped-on harness (expertly tied with a slip knot created by my husband, Mr. Ott), while pulling as many pennies in the sled as the animal can manage.

Each first grade boy at a given lab table has a job:  one slowly adds pennies, making sure that the bess beetle can pull (even if only a small tug) before another penny is added; another boy keeps the animal moving with a gentle touch; and the third keeps the path smooth in front of the animal.  The sharp peds of a bess beetle cannot grip smooth lab table tops, and the animal will try to go around any obstacle in its path, such as a "bump" of paper towel.  The "winning" animal and its lab team are awarded with their photograph on the science department page in the school’s yearbook, The Keg.

At the conclusion of the penny pull, which takes about 10-15 minutes, the boys are required to report the total number of pennies their beetle pulled to me.  I do the calculations for each table:  the gram weight of the total pennies and the gram weight of the pennies and the sled.  The sled alone weighs about three times as much as the animal!  To understand what the bess beetle accomplished, we convert the work it did into its "pulling power" by dividing the total weight that it pulled by the weight of the animal.  This is then translated into what a standard first grader (who weighs approximately 55 pounds) would have to weigh in order to do the same job.  It’s amazing; the boys would have to weigh as much as 600-1,200 pounds in order to do the equivalent job --that’s about the weight of a baby elephant!  It's very impressive.

We conclude the experiment with a discussion of how humans manage to do heavy work (introducing the concept of simple machines as tools--the wheel, the pulley, the lever, the wedge, and the screw) and discuss the bess beetle’s strong exoskeleton, which is its only defense against predatory birds and lizards and protection for its "heavy" living environment--the wood of a dead tree.