HOST DISCRIMINATION BY THE APHID PARASITOID APHELINUS ASYCHIS (HYMENOPTERA: APHELINIDAE): WHEN SUPERPARASITISM IS NOT ADAPTIVE

Abstract

Females of the solitary parasitoid Aphelinus asychis Walker discriminated between unparasitized and parasitized second-instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris). Wasps normally avoided superparasitism, except when they were confined with few hosts for a long time. Parasitoid females did not need previous experience with unparasitized aphids (learning) in order to discriminate. They probed with the ovipositor any aphids encountered, a behaviour suggesting that host acceptance and rejection were determined by internal cues. Prolonged ovipositor insertion (>80 s) was correlated with host acceptance and egg deposition, but short insertion times (≤80 s) generally indicated host rejection. Females tended to reject both self- and conspecific-parasitized aphids when provided with two of each kind. We consider hypotheses mat conspecific superparasitism may be adaptive and give examples to show exceptions. We propose that, in egg-limited parasitoid species such as A. asychis, a reproductive strategy based on the regulation of egg production and on oosorption can explain the equal avoidance of self and conspecific superparasitism.

Fitness consequences of superparasitism and mechanism of host discrimination in the stemborer parasitoid Cotesia flavipes

“…Our results indicate that the fitness consequences of superparasitism in C. flavipes are a prolonged development time, a decreased survival probability of the progeny and smaller size of the ensuing adults (Table 1, Figure 2). Our results support data from other studies, suggesting that superparasitism delays the development of the progeny (e.g., Wylie, 1983;Eller et al, 1990;Harvey et al, 1993), increases larval mortality (e.g., Vinson & Sroka, 1978;Vet et al, 1994) and results in smaller offspring (e.g., Harvey et al, 1993;Vet et al, 1994; but see for exception Bai & Mackauer, 1990).…”

“…For several parasitoid species it has been demonstrated that naive females (with no previous oviposition experience) have the ability to discriminate between parasitized and unparasitized hosts. Naive females may reject parasitized hosts (Bai & Mackauer, 1990;Völkl & Mackauer, 1990) or may lay significantly smaller clutches in parasitized hosts compared to unparasitized hosts. The latter has been demonstrated for Trichogramma evanescens (van Dijken & Waage, 1987), Cotesia glomerata (Ikawa & Suzuki, 1982) and Pediobius foveolatus (Hooker & Barrows, 1992).…”

Recognition of individual-specific marked parasitized hosts by the solitary parasitoid Epidinocarsis lopezi

“…differences in sex allocation (van Dijken and Waage 1987). Thus, consequently the studies of Aphelinus asychis (Bai and Mackauer 1990), Asobara tabida (van Alphen and Nell 1982) and Trichogramma evanescens (van Dijken and Waage 1987) are inconclusive as to whether wasps recognize different host types.…”

Host marking behavior in phytophagous insects and parasitoids

“…Females in some hymenopteran parasitoids are less likely to superparasitize hosts they themselves parasitized than hosts parasitized by conspecifics (Völkl & Mackauer, 1990;van Dijken et al, 1992;van Baaren et al, 1994;Danyk & Mackauer, 1993; but also see Bai & Mackauer, 1990;van Dijken & Waage, 1987;and van Alphen & Nell, 1982). Discrimination of self and non-self within these systems, often thought to be mediated by MP, is potentially adaptive because eggs deposited in a host parasitized by another female are potential competitors of the superparasitizing female's offspring, whereas eggs deposited in a host parasitized by the same female will increase competition among genetic relatives (van Dijken et al, 1992).…”