SATIATION EFFECTS ON OLFACTORY ORIENTATIO N PATTERNS OF COLORADO POTATO BEETLE FEMALES

Food-deprived insects are more responsive to food stimuli than replete d ones. The motivation to search for food is, thus, expected to be rel ated to factors like hunger. By detailed analysis of the orientation p atterns wing a locomotion-compensator, we have studied the effects of satiation on the olfactory responses of Colorado potato beetle (Leptin otarsa decemlineata Say) females to host-plant odour. Our results conf irm that starved females release an odour-conditioned positive anemota xis when stimulated by potato plant odour. When being repleted all the variables used to describe the orientation patterns are affected. The mast pronounced effects are that the beetle's walking speed is reduce d and the upwind direction of locomotion is changed into an alternatio n of upwind and downwind movements. After restarvation, the females re cover the control of their speed and positive anemotaxis. The results are discussed in the light of observation made on other insect species .