Academic journal article The American Biology Teacher

I Walk the Line: A Popular Termite Activity Revisited

Academic journal article The American Biology Teacher

I Walk the Line: A Popular Termite Activity Revisited

Article excerpt

In the years since the most recent review of the use of insects as teaching organisms (Matthews et al., 1997), many additional insect species and systems have migrated from the research laboratory to the classroom. Without a doubt, one of the most popular activities has been a simple exercise that involves termites and lines drawn with a ballpoint pen. Termite line-following has even captured attention on the Internet in the form of PDF files and YouTube videos. A simple Google query, "Why do termites follow ink," yields some 174,000 hits.

This attention is well deserved. Doing this activity engages students with real science, and the activity is easy, reliable, and inexpensive. However, much of the published and online information about it is redundant, inaccurate, or conflicting. Very few of the activity suggestions are inquiry based, and none provide a history of the activity or an entree into pertinent entomological literature. Thus, it seems appropriate to update and extend this activity, including suggestions for new hands-on inquiry-based activities adaptable to various levels of instruction.

* Background

Any of the common subterranean termites in the genus Reticulitermes (5 species are recorded from the United States) is appropriate for this activity. These termites occur in all but the highest elevations and most arid areas of the United States. Quantities can be collected easily during the warmer months from decaying damp logs or other wood debris in forests and parks. One can simply shake infested wood over a plastic wastebasket or storage container to dislodge the insects. (Smooth plastic container sides are difficult for termites to walk upon, ensuring that they do not escape.) Care requires only daily misting with a water spray bottle and provision of some damp wood pieces for the termites to eat. Groups of collected termites will survive for some time under these conditions. Alternatively, living termites are available from Carolina Biological Supply Co. (Burlington, NC) and Ward's Natural Sciences (Rochester, NY).

Collected termites will be of two forms. The most numerous are the sterile workers, which have small, soft heads; the less abundant soldiers have distinctly larger, darker heads and strong mandibles (Figure 1). Termites are among the most social of insects. An entire colony contains thousands of workers, hundreds of soldiers, and one or more fertile kings and queens; all are necessary for the group to survive and thrive. For this reason, worker termites that might escape or disappear during classroom activities pose absolutely no threat to wood in classroom buildings. More information on the biology of Reticulitermes can be found in Thorne et al. (1999).

Every day or night, a great many termite workers must leave the nest and search for new sources of food and water. Then, upon finding potential provisions, they must somehow relay a message back to the others to help in the harvest. A food-searching termite forager deposits scent marks as it wanders, a fact first experimentally demonstrated fewer than 40 years ago (Tschinkel & Close, 1973). Even if it does not find food, the termite can follow these scented droplets homeward. However, a successful termite returning home not only follows these droplets but also adds to its trail, laying down more droplets at greater concentration and at more frequent intervals. Other individuals that the worker encounters are stimulated to track the odor to the food source, reinforcing the track with their own scent marks. Over a relatively short time, these droplets become a more-or-less continuous chemical communication trail.

The chemistry of these communication chemicals, called pheromones (Wyatt, 2003), is now known for at least 60 termite species. Every termite species makes its own particular multicomponent cocktail (see reviews by Costa-Leonardo et al., 2009; Bordereau & Pasteels, 2011) and secretes it from glands located on the underside of their abdomens. …

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