Flexible use of patch-leaving mechanisms in a parasitoid wasp
Burger, J.M.S. ; Huang, Y. ; Hemerik, L. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2006
Journal of Insect Behavior 19 (2006)2. - ISSN 0892-7553 - p. 155 - 170.
encarsia-formosa hymenoptera - vaporariorum homoptera-aleyrodidae - time allocation - trialeurodes-vaporariorum - host relationship - infochemical use - commercial glasshouse - population-dynamics - volatile emissions - venturia-canescens
Classical optimal-foraging theory predicts that a parasitoid is less likely to leave a patch after a host encounter when the host distribution is aggregated, whereas a parasitoid is more likely to leave after a host encounter when the host distribution is regular. Field data on host distributions in the area of origin of the whitefly parasitoid Encarsia formosa showed that whiteflies aggregate at several spatial scales. However, infested leaves most likely contained a single host. This suggests that a host encounter is not enough to decide when to leave. We therefore tested the effect of host distribution and parasitoid experience on patch-leaving behavior. Each parasitoid was observed for several consecutive days in a three-dimensional arena with leaflets containing on average one host per leaflet in an either regular or aggregated host distribution. A proportional hazards model showed that a host encounter decreased the leaving tendency on a leaflet with one host when the time since the latest host encounter was short, but increased the leaving tendency when the time since the latest host encounter was long, independent of host distribution. We conclude that a parasitoid can switch from decreasing to increasing its tendency to leave a patch after a host encounter. We propose two hypotheses that may explain the evolution of such a switching mechanism.
Selection of Bemisia nymphal stages for oviposition or feeding, and host-handling times of arrhenotokous and thelytokous Eretmocerus mundus and arrhenotokous E. eremicus
Ardeh, M.J. ; Jong, P.W. de; Lenteren, J.C. van - \ 2005
BioControl 50 (2005)3. - ISSN 1386-6141 - p. 449 - 463.
encarsia-formosa hymenoptera - trialeurodes-vaporariorum homoptera - biological-control agents - life-history parameters - amitus-fuscipennis - aphelinid parasitoids - foraging behavior - aleyrodidae - tabaci - strategies
Host-handling behavior is an important aspect of parasitoid foraging behavior. When a parasitoid encounters a potential host, the handling behavior starts with the evaluation of the host and continues if the host has been judged acceptable. Host handling is usually terminated after egg laying or host feeding and host marking. Host-handling behavior of an arrhenotokous population of two Eretmocerus species, E. mundus Mercet and E. eremicus Rose and Zolnerowich, along with a thelytokous population of E. mundus were compared under laboratory conditions. Several elements of host-handling behavior, including encountering, ascending, turning on host, descending, preening, egg laying, and host feeding were recorded. There were no correlations among the durations of these phases across parasitoid populations/species or host nymphal instars. Duration of different phases of host-handling behavior showed only slight and sometimes significant differences between different Eretmoceruspopulations/species. The actual laying of the egg had the longest duration of all host-handling behaviors, and was longer on third nymphal instars than on younger ones. Females of the three populations/species accepted the first three nymphal stages either for egg laying or for host feeding. Females spent a lot of time to make wounds in the host when preparing for host feeding, and eventually killed the host. The implications of these findings for the use of the different Eretmoceruspopulations/species in biological control are discussed
Host feeding in insect parasitoids: why destructively feed upon a host that excretes an alternative?
Burger, W. ; Reijnen, T.M. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2004
Entomologia Experimentalis et Applicata 112 (2004)3. - ISSN 0013-8703 - p. 207 - 215.
trialeurodes-vaporariorum homoptera - encarsia-formosa hymenoptera - alfalfa weevil coleoptera - aphytis-melinus - honeydew sugars - aphelinidae - aleyrodidae - food - strategies - evolutionary
Host feeding is the consumption of host tissue by the adult female parasitoid. We studied the function of destructive host feeding and its advantage over non-destructive feeding on host-derived honeydew in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We allowed parasitoids to oviposit until they attempted to host feed. We either prevented or allowed host feeding. Parasitoids had access to sucrose solution, with or without additional access to honeydew. Parasitoids that were allowed to host feed did not have a higher egg load 20 or 48 h after host feeding than parasitoids prevented from host feeding. Host feeding did not increase the number of eggs matured within these periods, nor did the time spent host feeding positively affect any of these response variables. On the other hand, the presence of honeydew did have a positive effect on egg load 20 and 48 h after host feeding compared with parasitoids deprived of honeydew. Parasitoids with access to honeydew matured more eggs within these periods than honeydew-deprived parasitoids. Host feeding increased life expectancy, but this effect was nullified when honeydew was supplied after the host-feeding attempt. In conclusion, feeding on honeydew could be an advantageous alternative to host feeding in terms of egg quantity and longevity. This applies especially to parasitoids exploiting Homoptera, because these parasitoids can obtain honeydew from the host itself. It is possible that destructive host feeding has evolved to enable females to sustain the production of high-quality anhydropic eggs, which may be important in the parasitoid's natural environment. We argue that future studies should take natural alternative food sources into more consideration.
Searching and oviposition behaviour of Amitus fuscipennis, a parasitoid of the greenhouse whitefly
Manzano, M.R. ; Lenteren, J.C. van; Cardona, C. - \ 2002
Journal of Applied Entomology 126 (2002). - ISSN 0931-2048 - p. 528 - 533.
trialeurodes-vaporariorum homoptera - bemisia-argentifolii homoptera - encarsia-formosa hymenoptera - reproductive-biology - host relationship - aleyrodidae - aphelinidae - platygasteridae
Amitus fuscipennis MacGown & Nebeker (Hym., Platygasteridae) is a parasitoid of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hom., Aleyrodidae) on some crops as bean and snap bean ( both Phaseolus vulgaris L.) in Colombia. The searching and oviposition behaviour of A. fuscipennis was studied in the laboratory, using T. vaporariorum as a host on bean leaves. The parasitoid's basic search pathway consisted of walking, encountering the host, and drumming and probing it. While walking, the parasitoid stopped for short periods of time, partly to preen itself. Walking while searching comprised 61% of the adults' time budget and probing hosts represented 16%. After a host nymph was parasitized by A. fuscipennis, the parasitoid remained close by and continued searching for new hosts in the immediate vicinity. Such behaviour suggests area-restricted searching. The parasitoid preferred. first instars of T. vaporariorum for oviposition, resulting in long developmental times. Amitus fuscipennis had a high percentage of host acceptance resulting in a high percentage parasitism (60%) of all encountered hosts. Amitus fuscipennis, on average, walked faster before an oviposition (1.4 mm/s) than other whitefly parasitoids. The implications of these findings for the control of T. vaporariorum are discussed.