Parasitoids are equipped with a number
of mechanisms that enable them to deal with
the dichotomy between searching for hosts
(reproduction) and foraging for sugar
sources (energy). They possess separate cate-
gories of innate responses, which are
expressed relative to their physiological
needs (Wäckers and Lewis, 1994).
Associative learning is also organized along
separate physiological pathways. Lewis and
Takasu (1990) demonstrated that host- and
food-associated learning are separate entities
linked to the parasitoid’s physiological state.
Food-deprived parasitoids typically respond
by reducing their activity level, which can be
a direct consequence of energetic constraints
or a strategy to preserve the remaining
energy. Furthermore, they start to respond to
stimuli that are associated with food, such as
floral odours or colours (Wäckers, 1994;
Takasu and Lewis, 1995). Following feeding,
parasitoids switch back to searching for
hosts, choosing host-associated cues over
stimuli linked to food.
Foraging for food and searching for hosts
also interact on the spatial scale. Takasu and
Lewis (1995) showed that parasitoids tend to
concentrate their host search in the vicinity
of a successful feeding experience.
Conclusion
Biological control workers have long been
aware that the effectiveness of parasitoids
can be enhanced through the provision of
food sources (e.g. Illingworth, 1921; Wolcott,
1942; Hocking, 1966). Hocking (1966)
stressed the importance of food-source avail-
ability to the success of classical biological
control programmes. Others have advocated
the use of food supplements to support
native predators or parasitoids (Hagen, 1986;
Jacob and Evans, 1998). This has resulted in
several (partly successful) attempts to
increase the effectiveness of biological con-
trol agents through either the use of flower-
ing non-crop plants (Bugg et al., 1987; Landis
et al., 2000) or the provision of artificial food
sources (Hagen, 1986; Jacob and Evans,
1998). However, the choice of food sources is
often not based on adequate data, due to the
fact that basic information on the food ecol-
ogy of beneficial insects is scarce.
Comparative studies provide a promising
alternative, as they allow us to rate natural
or artificial food sources in respect of their
suitability as parasitoid food supplements.
Based on this information we can select the
optimal food supplements for use in para-
sitoid rearing, as well as for the enhancement
of parasitoid performance in the field.
The use of suitable food supplements in
mass rearing entails some specific benefits.
Due to the absence of many natural mortal-
ity factors under protected mass-rearing con-
ditions, the addition of food can enhance
parasitoid longevity and fecundity to levels
that exceed those resulting from food in the
field. Furthermore, in mass rearing, food can
be provided in the direct vicinity of the
hosts, which has the advantage that the
trade-off between search for hosts and food
foraging does not apply. The provision of
food supplements can also help reduce host-
feeding (undesirable in mass rearing), espe-
cially if suitable proteins are added to the
food supplement.Food Ecology and Mass Rearing in Biocontrol 67References
Alm, J., Ohnmeiss, T.E., Lanza, J. and Vriesenga, L. (1990) Preference of cabbage white butterflies and
honey bees for nectar that contains amino acids. Oecologia84, 53–57.
Avidov, Z., Balshin, M. and Gerson, U. (1970) Studies on Aphytis coheni, a parasite of the california red
scale, Aonidiella aurantii, in Israel. Entomophaga15, 191–207.
Baggen, L.R. and Gurr, G.M. (1998) The influence of food on Copidosoma koehleri(Hymenoptera:
Encyrtidae), and the use of flowering plants as a habitat management tool to enhance biological
control of potato moth, Phthorimaea operculella(Lepidoptera: Gelechiidae). Biological Control11, 9–17.
Baker, D.A., Hall, J.L. and Thorpe, J.R. (1978) A study of the extrafloral nectaries of Ricinus communis. New
Phytologist81, 129–137.