THE ROLE OF PHYSICAL CUES IN THE REGULATION OF HOST RECOGNITION AND ACCEPTANCE BEHAVIOR OF APHIDIUS-ERVI HALIDAY (HYMENOPTERA, BRACONIDAE)

The role of color and shape in the host recognition and acceptance beh avior of Aphidius ervi Haliday was studied. A quantitative analysis of the oviposition behavior of A. ervi was carried out with a computer-a ided analysis of 150 video-recorded oviposition sequences on its natur al host, Acyrthosiphon pisum (Harris). The importance of visual stimul i was assessed in a choice condition bioassay, observing the behaviora l reaction of female parasitoids to various test materials flame-seale d into glass capillaries. Glass beads 2 and 6 mm in diameter and a fla t arena were coated with cornicle secretion of A. pisum, and their acc eptance rates by both naive and experienced female parasitoids were as sessed under no-choice conditions. In most cases, A. ervi females swit ched from random searching to attack position when the host was within a range of I cm, suggesting that host recognition is regulated in par t by cues acting before physical contact. The glass capillary bioassay indicated that visual cues are important factors in the host recognit ion and acceptance phases. Pea aphid color alone can elicit the ovipos ition response of naive A. ervi females, and this response is enhanced when color is combined with aphid shape. The cornicle secretion of A. pisum stimulated an oviposition response which was stronger in naive females of A. ervi than in experienced ones and was not significantly affected by the glass bead size or flat surface. These results, along with those from previous studies, suggest that manipulation of the ovi position behavior of A. ervi is feasible under laboratory conditions.