parasitism (Askary and Brodeur, 1999).
When aphids are heavily infected by V.
lecaniiunder laboratory conditions, dense
aggregations of hyphae invade the host tis-
sues and the fungus penetrates the A.
nigripeslarvae. Under these circumstances,
infection of parasitoid tissues is localized. In
some cases, abundant hyphae are found in
the gut of A. nigripeslarvae, suggesting that
parasitoid larvae consume fungal spores and
hyphae when feeding on host haemolymph
and other tissues. However, there is no evi-
dence of invasion of the parasitoid tissues by
the fungus (Askary and Brodeur, 1999).
Further work is necessary to determine the
suitability of infected hosts for parasitoid
development and to quantify the effects of V.
lecaniion A. nigripesand other biological con-
trol agents under greenhouse conditions.
Aphidiusspp. that develop within cereal
aphids are infected by an entomophthora-
ceous fungus, probably Erynia neoaphidis
(cited by Brooks, 1993). However, it is not
known if the fungus invades the parasitoid
before or after death. Moreover, only two of
26 examined parasitoid larvae were colo-
nized by the fungus (cited by Brooks, 1993).
Aphytis (Aphelinidae): parasitoids of scale
insectsBACTERIA.About one-quarter of all Aphytis
species exhibit thelytokous parthenogenesis
(cited by Zchori-Fein et al., 1995), whereby
unfertilized females produce predominantly
female offspring. In these species, males are
produced regularly but usually at a low rate.
Wolbachiaspp. are associated with partheno-
genesis induction in several thelytokous
Aphytis species that exhibit reversible
parthenogenesis (A. chilensis Howard, A.
chrysomphali(Mercet), A. diaspidisHoward,
A. lingnanensis (Comp) and A. yanonensis
DeBach) (Zchori-Fein et al., 1995, 1998;
Gottlieb et al., 1998). Wolbachiaspp. are found
in the ovaries and eggs of thelytokous lines,
suggesting that these microorganisms are
transmitted transovarially (Zchori-Fein et al.,
1998). Treatment with rifampicin has been
successful in eliminating Wolbachia from
these lines (Zchori-Fein et al., 1995, 1998). A
phylogenetic analysis of Wolbachiaspp. from
four Aphytis species belonging to distant
phylogenetic groups place these Wolbachia
spp. in group ‘A’, together with the
parthenogenesis-inducing Wolbachia found
in Muscidifurax raptorGirault and Saunders.
The sequence analysis of two different
Wolbachia genes (16S ribosomal DNA
(rDNA) and ftsZ) results in the same phylo-
genetic tree (Zchori-Fein et al., 1995, 1998).
Virtually identical Wolbachiaspp. are found
in Aphytisspecies belonging to distant phy-
logenetic groups. This evidence suggests that
the horizontal transmission of Wolbachia
occurred recently in Aphytis.Cotesia(formerly Apanteles) (Braconidae):
parasitoids of Lepidoptera
VIRUSES.The survival or development of
Cotesia may be affected when their lepi-
dopteran hosts are infected with viruses.
Cotesia marginiventris (Cresson) failed to
develop within non-occluded virus-infected
Spodoptera frugiperda (J.E. Smith) that are
infected before or during parasitization. The
virus does not kill the host before C. mar-
giniventrisis able to successfully complete its
development. Rather, it is thought that either
the parasitoid eggs or the larvae are killed
when the host is inoculated (Hamm et al.,
1985). Cotesia melanoscelus(Ratzeburg) that
develop in Lymantria dispar (L.) larvae
infected with a nuclear polyhedrosis virus
carry viral polyhedra in their haemocytes
and fat body. However, parasitoid larvae
develop successfully in gypsy-moth larvae
infected with nuclear polyhedrosis virus
(cited by Brooks, 1993).PROTOZOA.Parasitoids of the genus Cotesia
are host to several species of microsporidia.
For example, Cotesia glomerata is susceptible
to Nosema aporivora, a pathogen of its host
Aporia crataegiL., C. marginiventrisis host to
Vairimorpha sp., a pathogen of its host
Heliothis zea(Boddie), and Cotesia rubecula
(Marshall) is host to N. mesnili, a pathogen of
its host Pieris brassicae (cited by Brooks,
1993).
Progeny of C. glomerata(L.) are host to
Nosema polyvora, a microsporidium that
infects P. brassicae(L.). Female parasitoidsPathogens of Natural Enemies and Pollinators 149