Search

Hoverflies (Diptera, Syrphidae) are cosmopolitan, generalist flower visitors and among the most important pollinators after bees and bumblebees. The dronefly Eristalis tenax can be found in temperate and continental climates across the globe, often synanthropically. Eristalis tenax pupae of different generations and different climate zones are thus exposed to vastly different temperatures. In many insects, the ambient temperature during the pupal stage affects development, adult size, and survival; however, the effect of developmental temperature on these traits in hoverflies is comparatively poorly understood. We here reared E. tenax pupae at different temperatures, from 10°C to 25°C, and quantified the effect on adult hoverflies. We found that pupal rearing at 17°C appeared to be optimal, with high eclosion rates, longer wings, and increased adult longevity. Rearing temperatures above or below this optimum led to decreased eclosion rates, wing size, and adult survival. Similar thermal dependence has been observed in other insects. We found that rearing temperature had no significant effect on locomotor activity, coloration or weight, despite evidence of strong sexual dimorphism for each of these traits. Our findings are important as hoverflies are key pollinators, and understanding the effects of developmental temperature could potentially be useful for horticulture.

The ability to visualize small moving objects is vital for the survival of many animals, as these could represent predators or prey. For example, predatory insects, including dragonflies, robber flies and killer flies, perform elegant, high-speed pursuits of both biological and artificial targets. Many non-predatory insects, including male hoverflies and blowflies, also pursue targets during territorial or courtship interactions. To date, most hoverfly pursuits have been studied outdoors. To investigate hoverfly (Eristalis tenax) pursuits under more controlled settings, we constructed an indoor arena that was large enough to encourage naturalistic behavior. We presented artificial beads of different sizes, moving at different speeds, and filmed pursuits with two cameras, allowing subsequent 3D reconstruction of the hoverfly and bead position as a function of time. We show that male E. tenax hoverflies are unlikely to use strict heuristic rules based on angular size or speed to determine when to start pursuit, at least in our indoor setting. We found that hoverflies pursued faster beads when the trajectory involved flying downwards towards the bead. Furthermore, we show that target pursuit behavior can be broken down into two stages. In the first stage, the hoverfly attempts to rapidly decreases the distance to the target by intercepting it at high speed. During the second stage, the hoverfly's forward speed is correlated with the speed of the bead, so that the hoverfly remains close, but without catching it. This may be similar to dragonfly shadowing behavior, previously coined ‘motion camouflage’.

Responding rapidly to visual stimuli is fundamental for many animals. For example, predatory birds and insects alike have amazing target detection abilities, with incredibly short neural and behavioral delays, enabling efficient prey capture. Similarly, looming objects need to be rapidly avoided to ensure immediate survival, as these could represent approaching predators. Male Eristalis tenax hoverflies are nonpredatory, highly territorial insects that perform high-speed pursuits of conspecifics and other territorial intruders. During the initial stages of the pursuit, the retinal projection of the target is very small, but this grows to a larger object before physical interaction. Supporting such behaviors, E. tenax and other insects have both target-tuned and loom-sensitive neurons in the optic lobes and the descending pathways. We here show that these visual stimuli are not necessarily encoded in parallel. Indeed, we describe a class of descending neurons that respond to small targets, to looming and to wide-field stimuli. We show that these descending neurons have two distinct receptive fields where the dorsal receptive field is sensitive to the motion of small targets and the ventral receptive field responds to larger objects or wide-field stimuli. Our data suggest that the two receptive fields have different presynaptic input, where the inputs are not linearly summed. This novel and unique arrangement could support different behaviors, including obstacle avoidance, flower landing, and target pursuit or capture.

Die Zielgruppe der Jugendlichen und jungen Erwachsenen ist im Kontext der Corona-Pandemie in den Fokus gerückt. Wie wichtig es ist, die Gesundheit der Jugendlichen und jungen Erwachsenen zu fördern, wird durch diese Fokussierung betont. Vor diesem Hintergrund ist es wichtig, die wissenschaftlichen Grundlagen als Basis für wirksame Massnahmen und Interventionen zu aktualisieren. So ist sichergestellt, dass die Grundlage für Programme und Projekte auf dem neuesten Stand ist. Der vorliegende Bericht zeigt, weshalb sich ein Engagement für die Gesundheit von Jugendlichen und jungen Erwachsenen lohnt. Aufbauend auf wissenschaftlichen Erkenntnissen wird gezeigt, warum die Themen Bewegung, Ernährung und psychische Gesundheit wichtige Pfeiler für die Gesundheit im Jugend- und jungen Erwachsenenalter sind. Es werden Interventionen und bewährte Handlungsansätze und Empfehlungen vorgestellt. Autorinnen und Autoren: Kapitel 1 Einleitung und Kapitel 10 Schlussfolgerungen: Dr. phil. Fabienne Amstad Kapitel 2 Lebensphase: Prof. Dr. med. Joan-Carles Suris, Dr. Yara Barrense-Dias Kapitel 3 Grundlagen: Prof. Dr. med. Julia Dratva, Matthias Meyer, dipl. SozÖk, Prof. Dr. phil. Karin Nordström Kapitel 4 Chancengleichheit: lic. phil. Dominik Weber Kapitel 5 Medien: MSc Jael Bernath, Prof. Dr. Daniel Süss Kapitel 6 Bewegung: Prof. Dr. Suzanne Suggs Kapitel 7 Ernährung: Dr. Sophie Bucher Della Torre Kapitel 8 Psychische Gesundheit: Prof. Dr. Frank Wieber, Prof. Dr. Agnes von Wyl, Dr. Annina Zysset Kapitel 9 Zusammenspiel: MSc Ronia Schiftan, MSc Anne-Françoise Wittgenstein Mani