Comparison of Laboratory Methods for Estimating Wood Consumption Rates by Coptotermes formosanus (Isoptera: Rhinotermitidae)

Three methods of calculating wood consumption rates (milligrams of wood per gram of termite per day) by laboratory groups of the termite, Coptotermes formosanus Shiraki, were compared. Rates calculated from 6- and 8-week data confirmed that a model which assumed no termite mortality during the feeding trial significantly underestimated wood consumption. A second model which assumed a linear increase in mortality during the trial gave consumption rates for 42-day tests which did not differ significantly from those derived from a third model based upon actual mortality records. This suggests that consumption rates can be predicted accurately in 42-day experiments with a model that assumes mortality increases linearly. Wood consumption rates calculated at 8 weeks were lower than those at 6 weeks, indicating that feeding rates were declining. This occurred even though little or no mortality was observed beyond day 28. It is proposed that feeding trials be carried out only while wood consumption (milligrams of wood per gram of termite) remains constant. In 6-week trials, C. formosanus consumed 55.04 mg/g per day when termite biomass was based on a linear-mortality model. This was more than 16% greater than consumption at 8 weeks based on termite weight calculated with a no-mortality model (46.56 mg/g per day).