An increasing number of researchers are studying behaviour in the hopes of
understanding population dynamics or improving biological control efforts o
f insect pests by natural enemies. However, it is unclear exactly how behav
ioural studies will improve our understanding of these population level pro
cesses. In this paper we argue that in order to understand population level
processes, the problem must be approached from a population biology perspe
ctive. A comprehensive understanding of certain behaviours will provide lit
tle towards our understanding of host-natural enemy interactions. For examp
le, using an aphid-parasitoid model, we examined the effect that a commonly
studied behaviour, variance in host selection by aphid parasitoids, has on
aphid-parasitoid population dynamics. Differential host selection does not
qualitatively alter classic Nicholson-Bailey dynamics, but only results in
quantitative differences in aphid-parasitoid population sizes. Irrespectiv
e of the degree of aphid instar preference, a large increase in the number
of aphids is followed by a large increase in the number of parasitoids, dec
imating the aphid population. Thus, studying some behaviours, such as varia
nce in host selection, will not contribute substantially to an understandin
g of aphid-parasitoid population dynamics.