Playing the hare or the tortoise in parasitoids: could different oviposition strategies have an influence in host partitioning in two Aphidius species?

In this paper, we compare the host selection behaviours of two parasitoids, Aphidius rhopalosiphi and Aphidius picipes, in order to analyse whether behavioural adaptations to the defensive behaviour of their host (the grain aphid Sitobion avenae) could, in part, be responsible for the simultaneous presence of both species in cereal fields. The oviposition behaviour of A. picipes differed from that of A. rhopalosiphi by,including a number of 'fluttering wings' sequences followed by immobility It resulted in a 44 times longer host-handling time for A. picipes than for A. rhopalosiphi. Hosts attacked by A. picipes exhibited fewer defensive behaviours than hosts attacked by A. rhopalosiphi.. A. picipes and A. rhopalosiphi rejected respectively 0% and 53% of unparasitized hosts presenting cornicle secretions, one of the defensive means of aphids. Furthermore, A. picipes females rejected 100% of the hosts that were already parasitized, whereas A. rhopalosiphi was previously described to reject only 20 to 40% of such hosts. Such differences could be explained by the way the two species deal with the aphid defensive behaviour. Field analyses, showed that A. rhopalosiphi was already present in wheat fields in early April whereas A. picipes appeared later and only achieved a low level of parasitism. However, when both species were present simultaneously, they shared the same resource

New and updated convex shape models of asteroids based on optical data from a large collaboration network

Context. Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. These efforts already provided deep insight into physical properties of main-belt asteroids or large collisional families. Going into finer detail (e.g., smaller collisional families,asteroids with sizes ≲20 km) requires knowledge of physical parameters of more objects.Aims.  We aim to increase the number of asteroid shape models and rotation states. Such results provide important input for further studies, such as analysis of asteroid physical properties in different populations, including smaller collisional families, thermophysical modeling, and scaling shape models by disk-resolved images, or stellar occultation data. This provides bulk density estimates in combination with known masses, but also constrains theoretical collisional and evolutional models of the solar system.Methods. We use all available disk-integrated optical data (i.e.,classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as input for the convex inversion method, and derive 3D shape models of asteroids together with their rotation periods and orientations of rotation axes. The key ingredient is the support of more that 100 observers who submit their optical data to publicly available databases.Results. We present updated shape models for 36 asteroids, for which mass estimates are currently available in the literature, or for which masses will most likely be determined from their gravitational influence on smaller bodies whose orbital deflections will be observed by the ESA Gaia astrometric mission. Moreover, we also present new shape model determinations for 250 asteroids, including 13 Hungarias and three near-Earth asteroids. The shape model revisions and determinations were enabled by using additional optical data from recent apparitions for shape optimization

New and updated convex shape models of asteroids based on optical data from a large collaboration network

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New and updated convex shape models of asteroids based on optical data from a large collaboration network

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