TEMPERATURE PREFERENCES OF THE WESTERN SUBTERRANEAN TERMITE, RETICULITERMES-HESPERUS BANKS

The western subterranean termite, Reticulitermes hesperus Banks, exposed to temperature gradients of 26-47-degrees-C, preferred temperatures between 29-32-degrees-C. Termites were never found at temperatures >40-degrees-C. When exposed to temperature gradients of 5.8-43.6-degrees-C, workers preferred temperatures between 14 and 19-degrees-C. Soil temperatures varied with depth, exposure to sunlight, and season of the year. Surface soil temperatures in the sunlight exceeded 40-degrees-C only during post meridian readings from April through to October. Soil temperatures to a depth of 120 cm exceeded 14-degrees-C from April through to October, indicating adequate temperatures for foraging activity. Surface soil temperatures were below optimal foraging temperatures from November through to March, especially during the night and early morning. No thermal shadows existed at the 0800 h reading. Within 4h, the soil underneath the centre of the stone was significantly cooler than was the soil at the edge or exposed to sunlight. By late afternoon even the soil under the centre of the stone had increased to above 40-degrees-C. Thermal shadows provide refuge for surface foraging termites to avoid high temperatures.