Gone With the Wind : The Structure and Function of the Dung Beetle Wind Compass

Prevailing winds carry seafarers across oceans and guide insects on their journeys. The South African, ball-rolling dung beetle Kheper lamarcki depends on a range of compass cues, including the azimuthal position of the sun and the directed airflow of wind to steer its plotted course. In this thesis, I set out to further our understanding for how these insects benefit from the directional component of the wind, and how this information is combined with the directional information from their solar compass. In Paper I, I verify that the antennae are the sensors that support wind-guided straight-line orientation in the beetles. I further demonstrate that even though a single antenna can support wind-guided straight-line orientation, the wind compass benefits from the pair. In Paper II I proceed to characterise the detailed morphology of the wind sensor itself – the antennal Johnston’s organ. I find that the beetle’s Johnston’s organ shares the characteristic morphology found among other wind-orientating insects. In Paper III, me and my colleagues turn our attention to how dung beetles integrate the directional information given by multiple cues and found that the integration strategy at play is a weighted vector summation, in which the relative influence of each cue on the combined directional signal is given by its relative weight. In Paper IV, we expand on this study and propose that the parameter that determines the weight given to each cue is likely its contrast. Taken together, the work presented in this thesis highlights how the dynamic and adaptable insect compass system can guide the animal on its journey, despite the challenges it may face.