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 hyperparasitoid Dendrocerus carpenteri (Curtis produce patch marks. We tested if these marks inform a foraging female of the identity of the producer of the mark (the female herself or a conspecific female) and on the producer's success or failure in finding hosts in the marked area. We also tested if the responses to patch marks differ depending on the size and/or egg load of the female. On average, females walked shorter paths and spent less time in previously explored areas in comparison to control areas only if the area had first been explored successfully (host 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 between average values were recoreded. However, egg load also seemed to influence foraging decisions in those experiments where average values were not different between previously explored and control areas. Females with a low egg load tended to spend less time in previously explored areas than females with a high egg load. Average values therefore somehow obscured the individual responses to pathc marks. The results suggest that at least D. carpenteri females with a low egg load continuously apply a marking pheromone while walking. This pheromone seems to contain information on the identity of the producer. In addition, different pheromones seem to be applied depending on whether or not hosts are present in the area.