Optical and pheromonal orientation and memory for homing distance in the harvester termite Hodotermes mossambicus (Hagen)

Abstract

1. Hodotermes workers conduct both day and night harvesting expeditions in the open air. 2. The harvesting direction taken from the foraging hole is determined at the beginning of the foraging period. 3. Two systems of aboveground orientation can be employed: optical menotaxis and pheromonal (chemical) orientation. 4. Optical orientation is more precise than pheromonal orientation. If both parameters are experimentally set in competition, optical cues dominate over pheromonal cues when ever they can be utilized. 5. Pheromonal orientation is crucial in “diffuse-light” or “no-light” conditions. It is always essential in the close vicinity of the foraging hole. 6. The pheromonal source is the sternal gland. A field of pheromonal marks is built up along the main foraging direction. Pheromonal orientation is performed by klinotactic motion along the chemical field. 7. Termites going out from the nest tend to use pheromonal orientation more readily than those returning. 8. In addition to directional orientation, individual memory for the distance between the foraging hole and feeding place has been demonstrated in homing termites.