Behavioral responses to light and thermal gradients by the western drywood termite (Isoptera: Kalotermitidae)

Abstract

The hypothesis that western drywood termite, Insicitermes minor (Hagen), nymphs are negatively phototactic was tested. Significantly more nymphs were found under the covered half of a petri dish than under the uncovered half exposed to either incandescent or fluorescent light, whereas there was no significant preference for either the covered or uncovered side when exposed to red darkroom light. The behaviors of I. minor nymphs when placed on temperature gradients for 24 h at 10, 30, or 50% RH were videotaped, analyzed, and quantified to test the hypothesis that I. minor nymphs actively avoid and move away from hot and cold temperatures. I. minor nymphs avoided temperatures >45°C and <12°C, formed aggregations away from the hottest or coldest temperatures and aggregated in the absence of a gradient. The distributions of termites on heated or cold gradients were significantly different from the controls and were not affected by relative humidity. Aggregations formed faster on heated gradients than on cool gradients while both formed faster than on the controls. Mean temperature preference values (mTVP) were significantly higher than the coolest temperatures on the cold gradients and significantly lower than the hottest temperatures on the heated gradients. Relative humidity did not have a significant effect on mTPV. The results of this study provide strong support for the theory that I. minor colonies relocate within structures or pieces of wood to avoid unfavorable conditions within their galleries.