The emergence of a caste-based reproductive division of labor marks one of the great events in the evolutionary history of life. Eager to shed light on how this transition occurred, Hans came to the Wossler lab to study solitary wasps with ancestor-like traits to social ones. For example, Synagris cornuta, a solitary vespid that cares for its young as it grows, alternates between reproductive and brood care phases that correspond, respectively, to the queen and worker phenotypes of her social relatives. After spending months in the field describing their behavior (that good old natural history), the wasps were collected for physiological processing, including ovary dissection, hormone measurements and the quantification of communicative chemical bouquets on the exoskeleton. Phase-specific differences of these parameters can help explain how, mechanistically, queens and workers were created from solitary antecedents.

 

In addition, Hans studied both native and invasive paper wasps of Stellenbosch, following up on his doctoral research (University of Washington with Lynn M Riddiford) that examined endocrine functions in Neotropical wasps, with special emphasis on juvenile hormone (JH), a phylogenetically ancient and pleiotropic hormone regulating insect metamorphosis, reproduction and associated behavior. His work has revealed that in social wasps JH functions are surprisingly labile, having apparently been modified to suit a variety contexts of social lifestyles, an evolutionary tinkering we are only now just beginning to understand.

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Hans completed his post-doctoral research in 2016 and is now working in the United States.