ceccidomyiid larvae and coccinellids showed no preference for healthy or parasitized (mummified) aphids (Colfer and Rosenheim 2001; Brodeur and Rosenheim
2000). The mummy provides not enough protection for the parasitoid, since it can
easily be torn by the mandibles of the coccinellids or pierced by the stylets of
predatory bugs and lacewings. The small bite can also result in fatal effects of the
pupa or led to emergence of a defective adult. It is not always easy to recognize the
attacked mummies of the second group, indicated only by small holes with darkened
margins. Dense aggregations of aphidiine mummies may be preyed upon through
sucking by the mandibles of the chrysopid larvae, which results in the presence of
two very small apertures in a mummy which is but actually dead and empty
(Al-Rawy et al. 1969). The larvae of syrphid flies are likely have less preference
on the parasitized aphids, since they are either unable to open the mummy with their
mouthparts or they could not recognize the mummies as suitable food source/pray
(Meyhöfer and Klug 2002).
It is evident that the parasitized aphids produce more honeydew, that is likely
attracting the aphid predators (Carter and Dixon 1984), therefore the parasitized
aphids are more vulnerable to the attacks by predators which use honeydew as
contact kairomone. Predation on the mummies by the coccinellids can be very
heavy in the field (Colfer and Rosenheim 2001). The heavy predation may disrupt
regulation of host aphid populations by the parasitoids. On the other hand, the
successful results of the combined effects by the aphid parasitoids and predators
(Rosenheim et al. 1997) cannot be overlooked. The effects of natural enemies in this
system are non-additive (Snyder and Ives 2003). Ecologically, the competitive
interaction of the predator-parasitoid can suppress efficiency of parasitoid, but the
predator can regulate the population of the pest aphid, solely (Costamagna et al.
2007) or within a diverse assemblage of the predators (Snyder et al. 2006). In the
positive view, the predators may have a regulatory effect on the parasitoids on the
same way that suggested for the hyperparasitoids. The negative effect of predation
has a dynamic nature and can be affected by the habitat complexity (Janssen et al.
2006), migrations (Briggs and Borer 2005), or the availability of alternative
resources (Daugherty et al. 2007).
The adult parasitoids can also be preyed by the predatory insects. It is not a rare
phenomenon, when the anthocorids feed on the adult aphid parasitoids among the
aphid colony. The carabids, lady beetles and staphylinid beetles as well as the
spiders are known as predators of the adult aphid parasitoids (Traugott et al.
2012). There are some evidences indicated the existence of some behavioral or
chemical defensive behavior in the adult parasitoids against the generalist predators
(Godfray 1994; Völkl 1997; Wells et al. 2001), but it needs to be further investigated
in the case of aphid parasitoids. The situation is more complicated in the case of
some parasitoids, like Lysiphlebus fabarum (Marshall), which adapted in the
ant-attending aphid colonies. The ants act as effective guards for the tended aphids
in warding off the predators (Jiggins et al. 1993). In the absence of protecting ants,
all developmental stages of L. fabarum suffered from a high risk of predation.
Foraging females of L. fabarum did not show an effective defence behavior even
in direct confrontations with the predator species, while they are able to kill the adult
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
369
2000). The mummy provides not enough protection for the parasitoid, since it can
easily be torn by the mandibles of the coccinellids or pierced by the stylets of
predatory bugs and lacewings. The small bite can also result in fatal effects of the
pupa or led to emergence of a defective adult. It is not always easy to recognize the
attacked mummies of the second group, indicated only by small holes with darkened
margins. Dense aggregations of aphidiine mummies may be preyed upon through
sucking by the mandibles of the chrysopid larvae, which results in the presence of
two very small apertures in a mummy which is but actually dead and empty
(Al-Rawy et al. 1969). The larvae of syrphid flies are likely have less preference
on the parasitized aphids, since they are either unable to open the mummy with their
mouthparts or they could not recognize the mummies as suitable food source/pray
(Meyhöfer and Klug 2002).
It is evident that the parasitized aphids produce more honeydew, that is likely
attracting the aphid predators (Carter and Dixon 1984), therefore the parasitized
aphids are more vulnerable to the attacks by predators which use honeydew as
contact kairomone. Predation on the mummies by the coccinellids can be very
heavy in the field (Colfer and Rosenheim 2001). The heavy predation may disrupt
regulation of host aphid populations by the parasitoids. On the other hand, the
successful results of the combined effects by the aphid parasitoids and predators
(Rosenheim et al. 1997) cannot be overlooked. The effects of natural enemies in this
system are non-additive (Snyder and Ives 2003). Ecologically, the competitive
interaction of the predator-parasitoid can suppress efficiency of parasitoid, but the
predator can regulate the population of the pest aphid, solely (Costamagna et al.
2007) or within a diverse assemblage of the predators (Snyder et al. 2006). In the
positive view, the predators may have a regulatory effect on the parasitoids on the
same way that suggested for the hyperparasitoids. The negative effect of predation
has a dynamic nature and can be affected by the habitat complexity (Janssen et al.
2006), migrations (Briggs and Borer 2005), or the availability of alternative
resources (Daugherty et al. 2007).
The adult parasitoids can also be preyed by the predatory insects. It is not a rare
phenomenon, when the anthocorids feed on the adult aphid parasitoids among the
aphid colony. The carabids, lady beetles and staphylinid beetles as well as the
spiders are known as predators of the adult aphid parasitoids (Traugott et al.
2012). There are some evidences indicated the existence of some behavioral or
chemical defensive behavior in the adult parasitoids against the generalist predators
(Godfray 1994; Völkl 1997; Wells et al. 2001), but it needs to be further investigated
in the case of aphid parasitoids. The situation is more complicated in the case of
some parasitoids, like Lysiphlebus fabarum (Marshall), which adapted in the
ant-attending aphid colonies. The ants act as effective guards for the tended aphids
in warding off the predators (Jiggins et al. 1993). In the absence of protecting ants,
all developmental stages of L. fabarum suffered from a high risk of predation.
Foraging females of L. fabarum did not show an effective defence behavior even
in direct confrontations with the predator species, while they are able to kill the adult
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
369