The foraging behaviour of the aphidiid wasps Lysiphlebus cardui and Aphidius funebris was analysed when a single hyperparasitoid female (Alloxysta brevis, Alloxysta victrix or Dendrocerus carpenteri) was searching simultaneously in the same aphid colony. Patch residence times and oviposition numbers of L. cardui and A. funebris searching in colonies with hyperparasitoids were not significantly different from those for aphidiid females searching in colonies without hyperparasitoids. Furthermore, the oviposition rate after the first contact with a hyperparasitoid female did not differ significantly from the control, both in L. cardui and A. funebris. We conclude that the presence of hyperparasitoid females does not directly influence the foraging behaviour of the aphidiid females.
1. Females of the aphid hyperparasitoid Dendrocerus carpenteri (Curtis) search successfully for hosts during both day and night. Oviposition numbers per host patch did not differ significantly between day and night.2. D.carpenteri females also displayed a nocturnal flight activity, showing that they are not only capable of searching on a given host plant but also of dispersing between host plants.3. Nocturnal oviposition activity was mainly influenced by egg load. Females with a high egg load laid more eggs at night than females with a comparatively low egg load. Thus, D.carpenteri females may use nocturnal foraging to compensate for the lack of oviposition opportunities during day.4. D.carpenteri females which foraged continuously for hosts both day and night (= for 24 h per day) benefitted from an 1.4-fold increase in lifetime reproductive success when compared to females which foraged only by day (= for 16 h per day).5 . The benefit of night foraging for this species is a significantly increased reproductive success.
This study analysed Culicoides presence-absence data from 46 sampling sites in Germany, where monitoring was carried out from April 2007 until May 2008. Culicoides presence-absence data were analysed in relation to land cover data, in order to study whether the prevalence of biting midges is correlated to land cover data with respect to the trapping sites. We differentiated eight scales, i.e. buffer zones with radii of 0.5, 1, 2, 3, 4, 5, 7.5 and 10 km, around each site, and chose several land cover variables. For each species, we built eight single-scale models (i.e. predictor variables from one of the eight scales for each model) based on averaged, generalised linear models and two multiscale models (i.e. predictor variables from all of the eight scales) based on averaged, generalised linear models and generalised linear models with random forest variable selection. There were no significant differences between performance indicators of models built with land cover data from different buffer zones around the trapping sites. However, the overall performance of multi-scale models was higher than the alternatives. Furthermore, these models mostly achieved the best performance for the different species using the index area under the receiver operating characteristic curve. However, as also presented in this study, the relevance of the different variables could significantly differ between various scales, including the number of species affected and the positive or negative direction. This is an even more severe problem if multi-scale models are concerned, in which one model can have the same variable at different scales but with different directions, i.e. negative and positive direction of the same variable at different scales. However, multi-scale modelling is a promising approach to model the distribution of Culicoides species, accounting much more for the ecology of biting midges, which uses different resources (breeding sites, hosts, etc.) at different scales.
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