Workshop

To understand how insects navigate in airborne odor plumes, we must first understand the spatiotemporal dynamics of the odor stimulus itself.  In most cases, this odor stimulus evolves in the presence of turbulent airflow, imparting complex structure.  In this talk, I will show how laser-based laboratory techniques can be used to visualize and quantify odor structure in turbulent flows in both air and water.  I will also describe a current multi-institutional project designed to elucidate and model the mechanistic brain function of animals navigating in odor plumes.  Finally, I will share recent laboratory measurements of human respiration plumes; these measurements might be useful to researchers in the insect community who are studying mosquito navigation, especially in the context of mosquitos as disease vectors.

The visual systems of animals are used to provide information that can guide behaviour. In the cases where insects demonstrate impressive visually-guided behaviour we might reasonably ask how the low-resolution vision and limited neural resources of these insects are tuned to these successful behavioural strategies. Such questions are of interest to both biologists and to engineers seeking to emulate insect-level performance with lightweight hardware. One behaviour that insects share with many animals is the use of learnt visual information for navigation. Ants, in particular, are expert visual navigators. Across their foraging life, ants can learn long idiosyncratic foraging routes. What’s more, these routes are learnt quickly and the visual cues that define them can be implemented for guidance independently of other social or personal information. Here we review the style of visual navigation in ants and consider the mechanisms that underpin it. Using historical and modern evidence we can sketch out the 'known-knowns' and 'known-unknowns' based on a perspective that robust navigation comes from the interaction of behavioural strategies, visual mechanisms and neural computation. 

• Silas Alben - Efficient locomotion of swimming foils and crawling snakes
• Orit Peleg - Optimal switching between geocentric and egocentric strategies in navigation
• Jordanna Sprayberry - Searching for the next meal: a computational exploration of sensory cues available to bumblebees searching for forage
• Lucia Jacobs - Olfactory navigation in vertebrates, a broad survey of evolutionary processes that have shaped olfactory navigation

The unique celestial compass system of South African dung beetles has been intensely studied for nearly 20 years. Diurnal and nocturnal African dung beetles use celestial cues such as the sun and moon and the skylight polarization pattern to roll dung balls along straight paths over the savanna. Although nocturnal beetles move in the same manner through the same environment as diurnal species, they do so when it is at least a million times dimmer.

We now know that the visual ecology of the beetle is linked to its orientation strategy and the neural activity of its compass neurons. At night, polarized skylight is the dominant orientation cue for nocturnal beetles. Diurnal beetles, however, persist in using a celestial body (the sun) for their compass. Compass neurons in the central complex of diurnal beetles are tuned primarily to the position of a simulated sun, while at lunar light intensities the same neurons in the nocturnal species switch exclusively to polarized light. Thus, these neurons encode the hierarchy of celestial cues and alter their preference according to ambient light conditions. This flexible encoding of the hierarchy of celestial cues relative to the prevailing visual scenery provides a simple, yet effective mechanism for enabling visual orientation at any light intensity.

A ball rolling beetle adhere stead-fast to its chosen course by the use of a simple orientation mechanism that facilitates precise navigation with minimal signal processing -  a “celestial snapshot” strategy. The enigmatic “dance”, performed on top of the ball prior to rolling, is the very moment when this celestial snapshot is taken and stored. When rolling, the beetles simply have to find the best match to this snapshot in order to hold their bearing.