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Abstract
Tunnel patterns of the Formosan subterranean termite, Coptotermes formosanus Shiraki, and its foraging behavior relative to the non-repellent wood preservative, disodium octaborate tetrahydrate (DOT), were studied in laboratory and field conditions using two-dimensional foraging arenas with multiple foraging sites. The initial frequency of tunnels entering arenas was uniformly distributed but became significantly skewed towards foraging sites farther out. This pattern occurred when wood was present and absent, suggesting that tunneling was affected by the physical aspects of discovered sites and not the presence of a food resource. Additional tests revealed that sites with open space elicited significantly more tunnels with a greater dispersion of tunnels outward from the point of site discovery than sites with solid food or non-food objects.
Tunnel width and segmentation were found to be significantly correlated to a foraging group's average worker size. Groups of larger workers constructed less segmented galleries with wider tunnels and were more efficient at discovering food items. Groups of smaller sized workers exhibited a slower rate of discovery but found the same amount of food items over time.
Discrete group of foragers from two different colonies showed no differences in amount of tunneling and wood consumption under controlled laboratory conditions; however, significant differences in tunneling and feeding were found when comparing the same two colonies in the field. Population estimates suggested that colony size could have been a factor. Observations on tunneling in the field over a three-day period revealed that tunneling might be related to air temperature with a lag effect.
The presence of treated wood to manufacturer recommended retentions of DOT did not deter termite tunneling in the surrounding substrate. Foragers continued to taste treated wood as it was moved to new locations, and they fed on untreated wood in locations previously occupied by treated wood. Foragers that ingested lethal amounts of borate from treated wood did not remain and die in the vicinity of the treated wood. Avoidance was more related to the location of treated wood than to recognition of the treatment. The potential role of pheromones in discretionary feeding is discussed.
