S.A.EL ARNAOUTY AND A. FERRAN*
Laboratory of Biological Control, Fac. Agric., Cairo University Cairo, Egypt
* Laboratoire de Biologie de Invertébrés, 37 bd du Cap 06606, Antibes , France

ABSTRACT

The third instar larvae of Chysoperla carnea, present two types of movements; extensive search (rapid, in straight line), and intensive search (slow, in sinuous line) which occurs after the ingestion of the first prey. For the determination of the searching efficiency, prey individuals (wingless females of Myzus persicae Sulz. and eggs of Ephestia kuehniella Zell.) were placed on the perimeter of four arenas of different diameters: 4, 7, 11 and 15 cm; 8 preys in each case. The predator larva was placed in the center. The predator was more efficient in finding its preys in the smaller arenas which represented higher prey densities. However, the predator was able to find out preys that were isolated. Prey- finding behavior seemed to be a non-random search, when preys were on arenas of 4 or 7 cm, and occasionally on 11 or 15 cm- diameter. In the smallest arena, the predator, located in the center, usually started extensive search until finding the first prey, then turned to an intensive search behavior. In such a case, the predator consumed 6.0±1.6 preys on the average. However, in 3% of the cases the predator larvae consumed all the 8 available preys. On the other hand, only 0.8±0.9 preys were attacked in the widest arena.

Key Words: Chysoperla carnea, Random/non-random search, Behavior, Predator-prey interaction.