Effects of Sand Moisture Level on Food Consumption and Distribution of Formosan Subterranean Termites (Isoptera: Rhinotermitidae) with Different Soldier Proportions

Formosan subterranean termites, Coptotermes formosanus Shiraki, were tested under laboratory conditions to determine preferences among different sand moisture levels in a choice test. Foraging behavior, rate of filter paper consumption and distribution patterns of the termites were studied among 3 soldier ratios: low (4% soldier), normal (16% soldier) and high (32% soldier) and 7 sand moisture gradients (4, 8, 12, 16, 20, 24 and 28% wt/wt) in a circular 3-dimensional arena. The results showed that sand moisture had a significant effect on termite distribution and filter paper consumption, whereas soldier proportions had no effect. Treatment means comparisons indicated that there were no significant differences in termite distribution or consumption among moisture levels ranging from 4 - 24%; however, significant differences were obtained when termite distribution or consumption on these moisture levels were compared with that of the saturated sand (28% moisture). Termites also were not present in the center release chamber (which had dry sand and no food) at any observation point. Within the range of 4 - 24%, we found a very uneven distribution pattern where 70 - 80% of the total released termites aggregated in 1 of the 6 moisture chambers. Filter paper consumption generally corresponded with the aggregation sites. Importantly, among the 27 replicates no particular moisture chamber was consistently chosen for aggregation indicating that Formosan subterranean termites probably can adapt to a range of substrate moisture levels in nature provided other conditions are suitable.