BEHAVIOR AND EFFECTIVENESS OF ADULT HIPPODAMIA CONVERGENS (COLEOPTERA, COCCINELLIDAE) AS A PREDATOR OF ACYRTHOSIPHON-PISUM (HOMOPTERA, APHIDIDAE) ON A WAX MUTANT OF PISUM-SATIVUM

Adult females of the coccinellid predator Hippodamia convergens (Say) spent more time walking and less time grooming on a line of peas, Pisu m sativum L., that has reduced waxbloom on all parts of the plant (due to the mutation wel) compared with a near-isogenic sister line with n ormal waxbloom. H. convergens walking was distributed over all parts o f the low-wax plants, whereas on normal-wax plants walking occurred mo stly on stems and the edges of leaves and stipules. The beetles were a ble to generate 30 times the adhesive traction force on leaf surfaces of low-wax plants compared with normal-wax plants. In cage studies, H. convergens (4 adults per plant) were more effective at reducing popul ation growth of pea aphid, Acyrthosiphon pisum (Harris), on low-wax pl ants than on normal-wax plants, but only at initial aphid densities of 10 aphids per plant. At higher initial densities (20 and 40 aphids pe r plant), differential impact of H. convergens was not observed or dis appeared after 4-5 d. The results indicate that reduced waxbloom in pe as could improve the effectiveness of H convergens on peas at low prey densities.