THE EFFECT OF PREDATOR AGE ON THE FUNCTIONAL RESPONSE OF PODISUS MACULIVENTRIS TO THE PREY SIZE OF GALLERIA MELLONELLA

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Abstract
Experiments were carried out to determine the effect of age on the functional response of the pentatomid predator Podisus maculiventris (Say), reared in a simple glass jar universe on different prey sizes of Galleria mellonella (L.). Holling’s (1959) ’disc’ equation accurately described the predator’s response at all prey sizes up to 50 days of life. For nymphs, the calculated ’rate of discovery’, a, increased as the predator age increased, but the time of handling prey, b, decreased; for both adult males and females, these calculated values increased gradually up to the 50th day. The relationship between predator age and numbers of prey killed, and predator age and amount of prey body contents consumed (food consumption), was linear at all prey sizes, but mainly negatively so. Prey size was an important component of the predation process for all stages of the predator.It is concluded that ’hunger’ is an important parameter of the attack model since the degree of predator satiation bears directly on b-type activities which in turn affects a-type activities. These findings indicate that under field conditions P. maculiventris will kill more small-sized lepidopterous prey larvae than large-sized ones, and that, because of the greater prey defense of the latter, their survival from predator attacks will increase. These actions may be of considerable importance in the survival of lepidopterous host species.