Protokoll der Jahresversammlung der Schweizerischen Entomologischen Gesellschaft vom 5. März und 21. Juni 2021 via Videokonferenz

Aufgrund der anhaltenden Corona-Pandemie musste die Jahresversammlung leider auf einen Tag reduziert werden und ohne physische Präsenz stattfinden. Sie wurde daher per Videokonferenz abgehalten. Der Präsident Oliver Martin hatte dafür ein Meeting via Zoom organisiert, das reibungslos ablief. Trotz der erschwerten Umstände konnte ein interessantes Vortragsprogramm für die Jahresversammlung zusammengestellt werden. Den Themenschwerpunkt bildete die experimentelle Forschung mit Hymenopteren, jedoch aus ganz unterschiedlichen Fachgebieten. Das Programm startete mit dem Hauptvortrag von Yuko Ulrich, Professorin an der ETH Zürich, zum Thema Sozialverhalten und Krankheitsdynamik bei Ameisen. Darin gab sie einen Einblick, wie im Labor soziale Interaktionen und die Mechanismen der Entstehung von Arbeitsteilung untersucht werden. Als Modellorganismus diente die räuberische Ameisenart Ooceraea biroi, die keine Königinnen ausbildet. Stattdessen vermehren sich alle Individuen parthenogenetisch, was den Faktor der genetischen Varianz in Experimenten deutlich reduziert. Mittels Kameras über mehreren Dutzend Ameisenkolonien und Farbcodes auf den Tieren konnte das Verhalten und der Aufenthaltsort (im Nest oder ausserhalb des Nests) jedes Individuums analysiert werden. Dann wurde der Einfluss der Koloniegrösse, sowie der Mischung von Genotypen und Körpergrössen innerhalb einer Ameisengruppe auf das Verhalten der Tiere untersucht. Abschliessend berichtete Frau Ulrich über die neueste Forschung mit experimentell infizierten Ameisen. Von Pilzsporen befallene Tiere werden intensiver von Artgenossen betreut, wodurch ihre Überlebensrate stark steigt. In zukünftigen Studien sollen die genannten Untersuchungen über mehrere Generationen von Ameisen hinweg ausgedehnt werden. ● Social behaviour and disease dynamics in clonal ant colonies. Yuko Ulrich, ETH Zürich ● Defensive symbionts protect aphids from parasitoid wasps depending on stable genotype-by-genotype interactions. Elena Gimmi, Eawag / ETH Zürich ● Megachile sculpturalis Smith, 1853 (Hymenoptera: Megachilidae), an Asian wild bee populates Europe. Julia Lanner, Universität für Bodenkultur Wien / Universität Bern ● Homemade or take away: Where do the cuticular hydrocarbons of parasitoid wasps come from? Corinne Hertäg, ETH Zürich ● Entwicklungsbiologische Ursachen sexueller Merkmale bei Mistkäfern: Wie macht man lange Beine? Patrick Rohner, Indiana University Der ETH Zürich sei für das Zurverfügungstellen des Videokonferenzraums herzlich gedankt.

Chemically Insignificant Social Parasites Exhibit More Anti-Dehydration Behaviors than Their Hosts

Social parasites have evolved adaptations to overcome host resistance as they infiltrate host colonies and establish there. Among the chemical adaptations, a few species are chemically “insignificant”; they are poor in recognition cues (cuticular hydrocarbons) and evade host detection. As cuticular hydrocarbons also serve a waterproofing function, chemical insignificance is beneficial as it protects parasites from being detected but is potentially harmful because it exposes parasites to desiccation stress. Here I tested whether the social parasites Polistes atrimandibularis employ behavioral water-saving strategies when they live at Polistes biglumis colonies. Observations in the field showed that parasites were less active than their cohabiting host foundresses, spent more time at the nest, and rested in the shadowy, back face of the nest, rather than at the front face, which contradicted expectations for the use of space for dominant females—typically, dominants rest at the nest front-face. These data suggest that behavioral adaptations might promote resistance to desiccation stress in chemical insignificant social parasites.

Aphids harbouring different endosymbionts exhibit differences in cuticular hydrocarbon profiles that can be recognized by ant mutualists

Cuticular hydrocarbons (CHCs) have important communicative functions for ants, which use CHC profiles to recognize mutualistic aphid partners. Aphid endosymbionts can influence the quality of their hosts as ant mutualists, via effects on honeydew composition, and might also affect CHC profiles, suggesting that ants could potentially use CHC cues to discriminate among aphid lines harbouring different endosymbionts. We explored how several strains of Hamiltonella defensa and Regiella insecticola influence the CHC profiles of host aphids (Aphis fabae) and the ability of aphid-tending ants (Lasius niger) to distinguish the profiles of aphids hosting different endosymbionts. We found significant compositional differences between the CHCs of aphids with different infections. Some endosymbionts changed the proportions of odd-chain linear alkanes, while others changed primarily methyl-branched compounds, which may be particularly important for communication. Behavioural assays, in which we trained ants to associate CHC profiles of endosymbiont infected or uninfected aphids with food rewards, revealed that ants readily learned to distinguish differences in aphid CHC profiles associated with variation in endosymbiont strains. While previous work has documented endosymbiont effects on aphid interactions with antagonists, the current findings support the hypothesis that endosymbionts also alter traits that influence communicative interactions with ant mutualists.

Aging-related variation of cuticular hydrocarbons in wild type and variant Drosophila melanogaster

The cuticle of all insects is covered with hydrocarbons which have multiple functions. Cuticular hydrocarbons (CHCs) basically serve to protect insects against environmental harm and to reduce dehydration. In many species, some CHCs also act as pheromones. CHCs have been intensively studied in Drosophila species and more specially in D. melanogaster. In this species, flies produce about 40 CHCs forming a complex sex- and species-specific bouquet. The quantitative and qualitative pattern of the CHC bouquet was characterized during the first days of adult life but remains unexplored in aging flies. Here, we characterized CHCs during the whole—or a large period of—adult life in males and females of several wild type and transgenic lines. Both types of lines included standard and variant CHC profiles. Some of the genotypes tested here showed very dramatic and unexpected aging-related variation based on their early days profile. This study provides a concrete dataset to better understand the mechanisms underlying the establishment and maintenance of CHCs on the fly cuticle. It could be useful to determine physiological parameters, including age and response to climate variation, in insects collected in the wild.

Cuticular hydrocarbons are associated with mating success and insecticide resistance in malaria vectors

Anopheles coluzzii females, important malaria vectors in Africa, mate only once in their lifetime. Mating occurs in aerial swarms with a high male-to-female ratio, where traits underlying male mating success are largely unknown. Here, we investigated whether cuticular hydrocarbons (CHCs) influence mating success in natural mating swarms in Burkina Faso. As insecticides are widely used in this area for malaria control, we also determined whether CHCs affect insecticide resistance levels. We find that mated males have higher CHC abundance than unmated controls, suggesting CHCs could be determinants of mating success. Additionally, mated males have higher insecticide resistance under pyrethroid challenge, and we show a link between resistance intensity and CHC abundance. Taken together, our results suggest that CHC abundance may be subject to sexual selection in addition to selection by insecticide pressure. This has implications for insecticide resistance management, as these traits may be sustained in the population due to their benefits in mating even in the absence of insecticides.