PROTOZOA.Beetles of the genus Hippodamia
are hosts to at least two described species of
microsporidia. Nosema hippodamiaewas the
first microsporidian pathogen described
from H. convergens collected in California
(Lipa and Steinhaus, 1959). This
microsporidium infects the midgut epithe-
lium and pupal fat body. Infected pupae
show no conspicuous external symptoms
and the adults and larvae are not infected. N.
hippodamiae occurs in localized epizootics.
There is no evidence that the disease is
severe in local populations. Spores are ovoid
and measure 3.3–5.4μm long ×2.2–2.7 μm in
width. Specimens infected with N. hippo-
damiaewere also infected with an unidenti-
fied eugregarine (Lipa and Steinhaus, 1959).
The microsporidium N. coccinellae was
found to infect H. tredecimpunctata from
Poland. Fresh spores are slightly larger than
those of N. hippodamiae and measure
4.4–6.7μm long × 2.3–3.4μm wide. This
microsporidium causes localized infections
of the midgut epithelium, Malpighian
tubules, gonads, muscles and nerves (Lipa et
al., 1975).
An undescribed microsporidium found in
H. convergensfrom California has spores that
are similar in size to those of N. hippodamiae.
The pathogen causes lesions in the midgut
epithelium and Malpighian tubules. The fat
body of infected beetles lacks vacuoles and
cell boundaries and has cell nuclei that are
hypertrophied. The disease begins in the fat
body and progresses to other tissues. The gut
is the last tissue to become infected (Sluss,
1968). Little is known regarding the effects of
microsporidia on the life-history characteris-
tics of Hippodamia.
H. tredecimpunctata, like C. septempunctata,
M. octodecimguttata, E. quadripustulatusand
H. quadripunctata, is host to the gregarine
parasite G. coccinellae(Lipa, 1967). For more
information on this disease, see Coccinella.
FUNGI.Three entomopathogenic fungi (B.
bassiana, M. anisopliae and P. fumoso-roseus)
with a broad host range show some degree
of virulence towards H. convergens(James
and Lighthart, 1994). First-instar beetle lar-
vae exposed to different concentrations of
fungal preparations in the laboratory exhibit
high mortality. However, the effects of these
fungi on Hippodamiaunder field conditions
are not known.Parasitoids (Hymenoptera)Endoparasitoid larvae develop within their
host where they may confront host
pathogens. As a result, parasitoids may be
affected by diseases from the host directly or
indirectly (Brooks, 1993). Most host–
parasitoid–pathogen interactions are detri-
mental to the parasitoid. Parasitoids may be
adversely affected due to the premature
death of the host, the presence of pathogen-
produced toxins in the host or the alteration
of host nutrition or physiology as a result of
infection. Furthermore, the parasitoid may
itself be susceptible to the host pathogen
(Brooks, 1993). We shall present only reports
of the latter case. For more information on
the other cases, see Brooks (1993).
Parasitoids may also be infected indepen-
dently of their host. Wolbachiainfections rep-
resent such a case. They are present in
several parasitoids used for biological pest
control and induce parthenogenesis (Aphytis,
Encarsia, Lysiphlebus, Muscidifurax and
Trichogramma), cytoplasmic incompatibility
(Nasonia) or elevated fecundity (Trichogramma).
These symbionts may cause little or no mea-
surable effect on parasitoid fitness (Zchori-
Fein et al., 2000); therefore, Wolbachiaspp. are
not always detrimental to natural enemies
(Chapter 8).Aphidius(Aphidiidae): parasitoids of aphids
FUNGI.Potato aphids (Macrosiphum euphor-
biae (Thomas)) parasitized by Aphidius
nigripesAshmead are susceptible to infection
by V. lecanii, an opportunistic fungus that is
commercially produced for aphid and white-
fly control in commercial cropping systems.
The application of Verticillium lecaniifor aphid
control can have an adverse affect on the sur-
vival of A. nigripes. When developing inside
an infected host, successful parasitoid devel-
opment is dependent on the timing of host
infection. Parasitoid survival increases if host
exposure to the fungus is delayed following148 S. Bjørnson and C. Schütte