APHIDS OR THEIR PARASITOIDS - WHO ACTUALLY BENEFITS FROM ANT-ATTENDANCE

1. The influence of ant-attendance on patterns of parasitism was studied for two parasitoid species attacking the black bean aphid Aphis fabae (Scop.), Trioxys angelicae (Haliday) and Lysiphlebus cardui (Marshall) on the host-plants Evonymus europaeus (L.) and Cirsium arvense (L.). 2. Foraging Trioxys angelicae females were heavily attacked by honeydew-collecting ants. However, ants did not treat Lysiphlebus cardui females in an aggressive way. 3. Ant-attendance provided a considerable protection for Aphis fabae against Trioxys angelicae, but did not prevent a high parasitization success of Lysiphlebus cardui. 4. Trioxys angelicae, which was restricted to unattended aphids, suffered from a high rate of hyperparasitization. In contrast, ant-attendance of parasitized aphids reduced the hyperparasitization of Lysiphlebus cardui significantly. 5. The increased honeydew-production of parasitized Aphis fabae led to an increase in the number of honeydew-collecting ants and additionally intensified the protection of the preimaginal stages of Lysiphlebus cardui. 6. Ant-attendance provided an 'enemy-free space' for the primary parasitoid Lysiphlebus cardui against its hyperparasitoids, which is a new aspect in parasitoid reproductive strategies.