AGE-SPECIFIC PATTERN OF HOST DISCRIMINATION BY THE APHID PARASITOID EPHEDRUS CALIFORNICUS BAKER (HYMENOPTERA: APHIDIIDAE)

Abstract

Can. Enr. 122: 349-361 (1990)The solitary aphid parasitoid Ephedrus californicus Baker is able to discriminate between unparasitized and parasitized third-instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris). Superparasitism varied with the number of mature eggs (which is age-dependent) present in the ovaries as well as with the number and the quality of any hosts encountered. Conspecific superparasitism varied with wasp age; older females, with a large egg supply, accepted hosts parasitized by a conspecific female if unparasitized aphids were unavailable. Self superparasitism occurred at all ages; it was the least likely behaviour compared with egg deposition in unparasitized and conspecific-parasitized hosts. Prior experience (learning) was not necessary for host discrimination, but it did influence the search rate, which was higher in inexperienced than experienced females. In choice experiments, wasps preferred conspecific-over selfparasitized aphids and thus were able to distinguish between them. It is suggested that oviposition markers vary among conspecific females. The data are discussed with reference to theories about oviposition decisions and progeny allocation in solitary hymenopteran parasitoids.Le parasito~de solitaire Ephedrus californicus Baker est capable de discriminer entre des nymphes de troisisme stade parasitkes et non-parasitkes du puceron du p i s , Acyrthosiphon pisum (Harris). Le niveau de superparasitisme a vari6 avec le nombre d'oeufs (qui dCpend de l'tige) prksents dans les ovaires ainsi qu'avec le nombre et la qualit6 de tout hBte rencontre. Le niveau de superparasitisme con-sp6cifique a vari6 avec 1'Lge des guepes; des femelles tigCes et posskdant une grande rCserve d'oeufs ont accept6 des hBtes parasitCs par une femelle con-spkcifique si des pucerons non-parasitks n'ktaient pas disponibles. Le superparasitisme personnel s'est produit i tous les Lges; c'6tait le comportement le moins probable lorsque comparC ? i la ponte d'oeufs dans des hBtes non-parasites ou parasitCs par des individus con-spkifiques. Une exp6rience antkrieure (apprentissage) n'a pas it6 nicessaire pour la discrimination d'hBtes, mais a influend le taux de recherche, lequel Ctait plus ClevC chez les femelles sans expkrience. Dans des tests de choix, les gu&pes ont prCfCrC des pucerons parasitks par des individus con-sp6cifiques i des pucerons parasitis par elles-m&mes et Ctaient donc capables de distinguer entre les deux. I1 est suggCr6 que les marqueurs d'oviposition varient entre les femelles con-spkifiques. Les donnCes sont discuties dans le contexte des thCories concernant les decisions d'oviposition et l'allocation de la progkniture chez des hymCnoptkres parasitoydes solitaires.

Host marking behavior in phytophagous insects and parasitoids

“…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.…”

“…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).…”

Influence of egg load and oviposition time interval on the host discrimination and offspring survival of Anagyrus pseudococci (Hymenoptera: Encyrtidae), a solitary endoparasitoid of citrus mealybug, Planococcus citri (Hemiptera: Pseudococcidae)

“…The decision of a parasitoid to oviposit in parasitized hosts may be influenced by both host availability and quality (van Lenteren, 1981;van Dijken & Waage, 1987), external and internal markers (Chow & Mackauer, 1986;Hofsvang, 1988), the physiological condition of the parasitoids (including the supply of mature eggs) (Volkl & Mackauer, 1990;Rosenheim & Rosen, 1991;Minkenberg et al, 1992) and the probability of offspring survival (Chow & Mackauer, 1986;Waage, 1986). The time interval since the previous oviposition may also influence the parasitoid's decision to oviposit in parasitized hosts (Chow & Mackauer, 1986), because any external marking of hosts during oviposition may not remain effective for more than a few days, and the females may then detect whether a host is parasitized by internal markers due to the quality of host changing during the growth of the parasitoid larva within the host.…”

Inter-specific variation in the reactive distance of different aphid-parasitoid associations: analysis from automatic tracking of the walking path

“…The reactive distance was estimated from the automatic analysis of videorecorded females' motion in the presence of fixed hosts. Host-searching behaviour is known to change according to egg depletion (Collins and Dixon, 1986;Völk and Mackauer, 1990), the previous experience of the females (Bell, 1990), and the presence of other foraging conspecifics (see Godfray, 1994). Thus, in order to estimate reactive distances under conditions that were as standardised as possible, experiments were based on video recordings of isolated, naive females.…”