cient numbers early in the season and
released to coincide with the codling moth’s
period of oviposition during the first genera-
tion, the moth might be suppressed to sube-
conomic densities (Flanders, 1930).
The Trichogramma species that Flanders
(1934) encountered on Vanessa cardui was
probably T. pretiosum, a species usually asso-
ciated with hosts in herbaceous and brushy
habitats in western North America, whereas
that parasitizing codling-moth eggs in the
west was probably T. platneriNagarkatti, a
species common on the eggs of arboreal
Lepidoptera (Pinto, 1998). T. platneri is a
member of the T. minutumcomplex. T. minu-
tumRiley is the eastern arboreal counterpart
of T. platneri, the western member of the com-
plex. They cannot be distinguished from each
other morphologically but they are reproduc-
tively incompatible, even though they readily
interbreed (Stouthamer et al., 2000). These
two species are reared by a number of insec-
taries. However, it is impossible to determine
which species comprises a culture – much
less whether the culture consists of a single
species. If T. minutumis released augmenta-
tively in western North America and encoun-
ters T. platneriin the field, the two species
will interbreed but no female offspring will
be produced from such matings. Thus, if the
eastern species is released within the western
species’ distribution or vice versa, the popu-
lation densities of both species will be
severely depressed because of the absence of
female offspring (Stouthamer et al., 2000).
This emphasizes the importance of under-
standing the systematic infrastructure of bio-
logical control agents, as has been repeatedly
emphasized by a number of biological con-
trol workers (e.g. Rosen, 1986; Gordh and
Beardsley, 1999; Stouthamer et al., 2000).
After Flanders (1934) tested several hosts
on which to mass-rear the wasp, including
the Mediterranean flour moth, Anagasta
(Ephestia) kuehniella (Zeller) (Lepidoptera:
Pyralidae), the potato tuber moth,
Phthorimaea operculella (Zeller) and the
Angoumois grain moth, Sitotroga cerealella
(Oliver) (Lepidoptera: Gelechiidae), he chose
S. cerealellaeggs reared on wheat kernels for
mass-producing Trichogramma. The total pro-
duction per unit weight of grain reached its
maximum much more quickly with wheat
than with maize kernels. However, he main-
tained his small cultures on maize because
they required less handling of equipment to
maintain the small colony. Thus, the rearing
system he employed depended on his rear-
ing objective, a part of which sought to mini-
mize rearing and maintenance costs. He
eliminated A. kuehniellaeggs as a host for
Trichogrammabecause it was much more sus-
ceptible to larval parasitism and its webbing
habits caused problems in handling the cul-
ture (Flanders, 1930). Better sanitary meth-
ods and rearing techniques have now
minimized these latter factors as problems
and A. kuehniellaeggs are also used for mass-
producing Trichogramma(e.g. Voegelé et al.,
1975; Bigler, 1986). The eggs of these two
moths are the principal hosts used to mass-
rear Trichogramma species except in the
People’s Republic of China (Smith 1996).
Eggs of the giant silkworms, Saamia cynthia
(Drury) (Lepidoptera: Saturnidae) and
Antherea perniyi (Gnérin-Mádneville)
(Lepidoptera: Saturnidae), and the rice-grain
moth, Corcyra cephalonica (Lepidoptera:
Pyralidae), are the principal hosts used in the
People’s Republic of China (Huffaker, 1977).Trichogrammasize, quality and reproductive
successIt has been known for some time that the size
of the host used by Trichogrammaor the num-
ber of Trichogrammaemerging from a host
influences the size of the emerging wasps.
For example, Howard and Fiske (1911) noted
that the size of emerging wasps was related
to the number of wasps with which they
emerged; in this case the host was the brown-
tail moth. Flanders (1930), in his monograph
on the mass-rearing of Trichogramma, men-
tioned that the host egg used for rearing this
wasp influenced the size, longevity and
fecundity of the emerging adult
Trichogramma. Similarly, Salt (1940) noted that
host size influenced the size of the emerging
adult: the smaller the host, the smaller the
wasp. However, it was Klomp and Teerink
(1962, 1967) who showed, in an elegant set of
experiments, that the wasp measured a host’s236 R.F. Luck and L.D. Forster