prospects of those produced by a parental
female with differing attributes (e.g. in
accepting larger or smaller hosts) (Dawkins,
1982, p. 179). Thus, a wasp’s reproductive fit-
ness can be viewed as having three compo-
nents: clutch size (= number of eggs laid per
host), her lifetime production of clutches and
her influence on the fitness of her offspring
arising from these clutches (e.g. offspring
size and sex). In solitary parasitoids, host
acceptance often involves the choice of host
size on which to lay female versus male off-
spring (Charnov, 1982; Godfray, 1994; van
Alphen and Jervis, 1996). This component is
important to augmentative biological control
with solitary, idiobiont parasitoids because
offspring usually develop on or in a single
host. A female thus influences the reproduc-
tive prospects of her offspring through her
choice of a host’s developmental stage and
size, which is often strongly correlated with
the sex of the offspring she allocates to it
(Charnov, 1982; Waage and Ng, 1984; Luck
and Podoler, 1985; Godfray, 1994; Kazmer
and Luck, 1995; van Alphen and Jervis, 1996;
Luck et al., 2000).
The theoretical underpinning of this
behavioural approach rests on the assump-
tion that, evolutionarily, those lineages that
have successfully reproduced in the past are
likely to be those that manifest host-selection
behaviours that maximize their offspring’s
reproductive prospects under current circum-
stances. Moreover, these are likely to be the
behaviours that are present in a population of
potential biological control agents. These
host-acceptance behaviours then set the lim-
its within which these agents can be expected
to exploit a particular host resource. They set
the conditions that influence a female’s
choice of hosts, in terms of both the degree to
which she will exploit them, as in the case of
T. platneriparasitizing S. aegrotataeggs, and
the number and sex of offspring she will allo-
cate to each of them (Waage and Ng, 1984;
Luck et al., 2000). This later, via offspring size
and associated egg load, influences their
likely encounter rates with hosts after they
emerge, as for example with T. pretiosumpar-
asitizing the eggs of T. ni, H. zeaand M. sexta
in the tomato fields of southern California
(Kazmer and Luck, 1995). Offspring inherit-
ing the behaviours associated with these
choices, i.e. host acceptance or clutch size in
relation to host size, are those most likely to
leave offspring that will themselves repro-
duce in subsequent generations. These
behavioural ‘choices’ form the basis for the
behavioural assessment utilized by van
Dijken et al.(1986) to evaluate host recogni-
tion and host acceptance (e.g. van Bergeijk et
al., 1989). It is the approach we have advo-
cated here but with the addition of an evolu-
tionary perspective. Thus, a natural
concordance exists between a parasitoid’s
reproductive fitness and biological control –
namely, how readily a parental female
oviposits in a host directly translates to the
prospects for biological control, both aug-
mentative and classical – and it arises histori-
cally from the reproductive success that the
lineage has had when choosing such hosts.Behavioural Approaches for Quality Control 243References
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