4 Variations in Natural-enemy Foraging

Behaviour: Essential Element of a Sound

Biological Control Theory

W.J. Lewis,^1 L.E.M. Vet,2, 3J.H. Tumlinson,^4 J.C. van Lenteren^2

and D.R. Papaj^5

(^1) Insect Biology and Population Management Research Laboratory, USDA-ARS,

PO Box 748, Tifton, GA 31793, USA;^2 Laboratory of Entomology, Wageningen

University, PO Box 8031, 6700 EH Wageningen, The Netherlands;^3 Netherlands

Institute of Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands;^4 Insect Biology

and Population Management Research Laboratory, USDA-ARS, PO Box 14565,

Gainesville, FL 32604, USA;^5 Department of Ecology and Evolutionary Biology,

University of Arizona, Tucson, AZ 85721, USA

Introduction

The often erratic performances of natural
enemies limits their use as pest-control
agents. In parasitoids, the ability of females
to locate and attack hosts is a key determi-
nant of how well a given parasitoid popu-
lation performs. Thus, the variation in this

host-location ability could be a major

source of inconsistent results in biological

control. The causes for variation in natural-

enemy foraging behaviour are currently

poorly understood, despite a substantial

body of theoretical and empirical literature

dealing with the subject. Most earlier inves-

tigations focused on extrinsic factors, such

© CAB International 2003. Quality Control and Production of Biological Control Agents:
Theory and Testing Procedures (ed. J.C. van Lenteren) 41

Abstract

Intraspecific intrinsic variation in foraging behaviour is a common but often overlooked feature of nat-
ural enemies. These variations result from adaptations to the variety of foraging circumstances encoun-
tered by individuals of the species. We discuss the importance of understanding the mechanisms
governing these intrinsic variations and the development of technologies to manage them. Three major
sources of variation in foraging behaviour are identified. One source for variation is genotypically fixed
differences among individuals that are adapted for different foraging environments. Another source of
foraging variation is the phenotypic plasticity that allows individuals to make ongoing modifications of
behaviour through learning, which suits them for different host-habitat situations. A third factor in deter-
mining variation in foraging behaviour is the natural enemy’s physiological state relative to other needs,
such as food and mating. A conceptual model is presented for comprehensively examining the respective
roles of these variables and their interactive net effect on foraging behaviour. We also discuss proposed
avenues for managing these variations in applied biological control programmes.