Determining growth factors responsible
for the full expression of the reproductive
capacities of arthropod predators remains a
major challenge. Results from recent studies
on the pentatomid predator P. maculiventris
suggest that adult nutrition is more critical
for fecundity than the diet of the immature
stages. In so called ‘rescue’ experiments, P.
maculiventrisfed artificial diet as nymphs but
transferred to live prey upon adult emer-
gence showed normal fecundity. Conversely,
nymphs fed prey and given the diet as adults
exhibited reduced fecundity (P.D. Greany,
unpublished data). However, Wittmeyer and
Coudron (2001) and Wittmeyer et al.(2001)
reported for the same species that switching
to live food in the adult stage still yielded
lower fecundity compared with predators
reared on insect prey in both nymphal and
adult stages. Adams (2000b) and Wittmeyer
et al.(2001) showed that predatory pentato-
mids fed on artificial diet do not have
impaired ovipositional abilities but lay fewer
eggs because they produce fewer mature fol-
licles than prey-fed controls.
Finally, measurement of fecundity is a
tedious and time-consuming activity if one
has to collect eggs over a long span of time.
Adams (2000a) and Wittmeyer et al.(2001),
and Shapiro et al.(2000) proposed methods to
reduce assay time by looking at first-cycle
oocyte development or at vitellin levels,
respectively. Further, instead of testing fecun-
dity during the entire female life, it could be
evaluated during a shorter period of time,
but this may not always be very reliable, as
observed in vivowith different Trichogramma
spp. (Silva, 1999; Grenier et al., 2002).
LongevityThe lifespan of mated females is a quality cri-
terion used in Trichogrammafor in vivorearing
in different conditions (Cerutti and Bigler,
1995; Dutton et al., 1996). Longevity is
reduced in T. pretiosumand T. galloireared in
vitrocompared with parasitoids reared in nat-
ural hosts (Consoli and Parra, 1996). On the
other hand, longevity is similar for the
tachinid fly E. larvarumobtained either in vivo
(on G. mellonella) or in vitroon artificial diets
(Dindo et al., 1999). No difference in longevity
of diet-reared and host-reared D. introitawas
noted by Greany and Carpenter (1998).
The longevity of female P. maculiventris
was not affected by diet (De Clercq and
Degheele, 1992; De Clercq et al., 1998a).
Whereas Adams (2000b) did not observe a
difference in longevity between diet-fed and
prey-fed females of P. bioculatus, a difference
was reported by Rojas et al.(2000).
Finally, it should be pointed out that the
relationships between longevity (or fecun-
dity) and the kind of food supplied (natural
vs. artificial) in parasitoids is completely dif-
ferent from that in most predators, because
the adults of the former group are non-car-
nivorous, even if they may occasionally
show some host-feeding. It is also necessary
to separate pro- and synovigenic parasitoid
species for their more or less close depen-
dence on their larval food.Biochemical parametersThe composition of key components in living
organisms, such as proteins, lipids, carbohy-
drates, enzymes and hormones, might be a
good criterion for estimating the quality of
artificially reared natural enemies.Proteins
Proteins are key constituents of living organ-
isms. Total amino acid content is a good indi-
cation of the viability of in vitro-reared
insects, but free amino acid level is a better
criterion for detecting unbalanced food. Total
amino acid content of T. dendrolimigrown in
artificial diet is strongly improved and
reaches nearly the level of that of parasitoids
grown in vivowhen proteins were added in
the diet. A better composition in amino acids
is correlated with improvements of biologi-
cal parameters. Free amino acid levels for T.
dendrolimigrown in vitro, especially on an
artificial diet with haemolymph, revealed
high excess in some amino acids, notably
serine (Grenier et al., 1995). The total amino
acid content of M. caliginosusreared on artifi-
cial diets showed less than 20% variation for
each amino acid compared with control bugs
reared on natural prey. The in vitro-grownQuality of Artificially Reared Biocontrol Agents 123