CRUDE AQUEOUS-EXTRACT (KAIROMONE) FROM APHIS-FABAE SCOP (HOM, APHIDAE) AND ITS EFFECT ON THE BEHAVIOR OF THE PREDATOR METASYRPHUS-COROLLAE FABR (DIPT, SYRPHIDAE) FEMALE

Female Metasyrphus corollae Fabr., a syrphid predator on the bean aphi d Aphis fabae Scop., responded to aqueous extract containing kairomone s of the prey. The crude aphid-extract was topically dropped onto clea n leaves of Vicia faba. After application of aqueous-extract at differ ent aphid densities on the clean leaves, the predator showed variation s in oviposition and searching behaviours in comparison with untreated leaves (control). The variations are summarized as follows: (1) the a queous-extract of aphids stimulate M. corollae females to lay eggs at all aphid densities. The number of eggs were directly proportional wit h aphid concentrations; (2) the predator M. corrolae female intensifie d its searching behaviour by increasing the total path length walked; (3) the number of turns exhibited is significantly higher as compared with those of control; and (4) the retention time spent by M. corollae females with treated plant is much more than that with clean plant at all aphid densities. The present results showed that the aphid aqueou s-extract contains the active ingredients (kairomones) which induce a considerable change in the searching pattern and increase the oviposit ion rate of the predator syrphid females.