Trail-following behavior of Coptotermes formosanus (Isoptera: Rhinotermitidae) on concentration gradients of 2-phenoxyethanol
The trail-following behavior of the Formosan subterranean termite, Coptotermes formosanus Shiraki was evaluated on chemical lines drawn with 2-phenoxyethanol. On non-gradient trails (one concentration), 80-100% of the tested termites responded to the trail with a concentration of 2-phenoxyethanol from 0.023-2.3 μg/cm and all responded to the trail at 0.23 μg/cm. The mean distance traveled increased with increasing concentration from 0.00023-0.23 μg/cm and was significantly greater at 0.023, 0.23, and 2.3 μg/cm than that in the control. More than 50% of the tested termites (53-87%) traveled and reached the end of the trail without reversing or leaving the trail at 0.23 or 2.3 μg/cm. No individuals traveled to the end of the trail at 0.00023, 0.0023, or 23 μg/cm. On gradient trails (a series of four concentrations), termites walking up the trail gradient (lowest to highest concentrations) stayed on the concentration gradients and traveled a significantly greater distance when the initial concentration went from 0.0023 to 2.3 μg/cm than those that went from 0.023 to 23 μg/cm. No termites completed the first gradient when the initial gradient was 0.00023 μg/ cm (increasing-trail gradient) or 23 μg/cm (decreasing-trail gradient). About 40-50% of the termites reversed their direction on the second gradient of the decreasing-gradient test (highest to lowest concentrations), but, in the increasing-gradient test, no termites reversed their direction on the second and the third gradient. Aggregation behavior to 2-phenoxyethanol was also observed.