Evidence for a two-component external marking pheromone system in an aphid hyperparasitoid

Abstract

The megaspilidDendrocerus carpenteri (Curtis) is a solitary ectohyperparasitoid of aphid primary parasitoids. It avoids superparasitism, but the avoidance rate depends on the amount of time elapsed after the first oviposition. In addition, females discriminate in a time-dependent manner between hosts parasitized by themselves and hosts parasitized by conspecifics. They recognize parasitized hosts by means of two externally perceivable chemical markers that are deposited on the mummy shell. One of the markers is highly active, short-lived, not passable through gas chromatography (GC), and freezing sensitive; the other is moderately active, persistent, GC-passable and freezing tolerant. Using two markers is believed to be advantageous for the hyperparasitoid female, as their ratio provides information on mark age and on the producer of the mark (the female herself or a conspecific female).

Host marking behavior in phytophagous insects and parasitoids

“…The propensity for certain entomophagous parasitoids to mark both the inside and the outside of the host (reviewed by van Lenteren, 1976;Hofsvang, 1990) may reflect a strategy of redundancy. Other parasitoids utilize a two-component chemical marking system; the deployment of more than one component in hostmarking has many possible explanations, of which redundancy is one (Höller et al, 1991).…”

“…Sometimes females show increased levels of host rejection with time; sometimes females initially show high levels of rejection but accept hosts more readily with time. Responses can also be complex; for example, levels of rejection may be high at first, then decline to some asymptote and remain stable (Höller et al, 1991). Alternatively, levels of rejection may be high, then decline and then increase again (Chow & Mackauer, 1986).…”

“…Female behavioral responses to a larval host that has been occupied for a given length of time may also not be a fixed species-specific pattern, but may be a condition-dependent one that varies with a female's experience level (Bosque & Rabinovich, 1979;Hubbard et al, 1999;Chow & Mackauer, 1986), rearing density (Visser, 1996), age and egg load (Völkl & Mackauer, 1990), and whether the mark encountered was produced by the female herself or by conspecifics (Hubbard et al, 1987;Höller et al, 1991;Gauthier et al, 1996). Where costs and benefits of host reuse vary under the above conditions, female rejection patterns are expected to vary accordingly.…”

“…One means for such discrimination is through use of a two-component marking system. In such a system, one of the marking components is shortlived and allows females to recognize hosts that they themselves have recently utilized, while the other component is long lived and provides general information regarding the host's status (Höller, 1991;Field & Keller, 1999). Alternatively, recognition of self versus conspecific parasitism may be mediated by variation in MP constituents.…”

Foraging for mates in the hyperparasitic wasp, Dendrocerus carpenteri: impact of unfavourable weather conditions and parasitoid age

“…The foraging behaviour and resource utilization of D. carpenteri females has been studied intensively (e.g. Walker and Cameron 1981;HoÈ ller et al 1991;Mackauer and Lardner 1995;VoÈ lkl and Kranz 1995;VoÈ lkl et al 1995;Chow and Mackauer 1996;Sullivan and VoÈ lkl 1999). Studies on the biology of males have been limited to courtship and copulation behaviour, showing that males copulate throughout their entire life.…”