PATCH MARKING IN THE APHID HYPERPARASITOID, DENDROCERUS-CARPENTERI - THE INFORMATION CONTAINED IN PATCH MARKS

The aim of this study was to test if females of the aphid hyperparasit oid Dendrocerus carpenteri (Curtis) produce patch marks. We tested if these marks inform a foraging female of the identity of the producer o f the mark (the female herself or a conspecific female) and on the pro ducer's success or failure in finding hosts in the marked area. We als o tested if the responses to patch marks differ depending on the size and/or egg load of the female. On average, females walked shorter path s and spent less time in previously explored areas in comparison to co ntrol areas only if the area had first been explored successfully (hos t found) by a conspecific female. If no host had been found or if the area had been explored by the same female previously, no differences b etween average values were recorded. However, egg load also seemed to influence foraging decisions in those experiments where average values were not different between previously explored and control areas. Fem ales with a low egg load tended to spend less time in previously explo red areas than females with a high egg load. Average values therefore somehow obscured the individual responses to patch marks. The results suggest that at least D. carpenteri females with a low egg load contin uously apply a marking pheromone while walking. This pheromone seems t o contain information on the identity of the producer. In addition, di fferent pheromones seem to be applied depending on whether or not host s are present in the area.