Meeting Abstract
Insects use many hairs of varying lengths for flow sensing. Wood crickets, equipped with an entire hair canopy on their cerci, use them to perceive wolf spiders which are hunting on the ground and launch attacks at high speed once in the neighborhood of their prey. Having measured and modeled the flow ahead of an attacking spider, we then predicted the reaction of the entire canopy of hairs to the transient signals produced. We discovered that hairs of all lengths can be optimal, each one being addressed at a specific instant of the interaction. The extent of negative and positive viscous coupling effects among the sensory hairs, quantified using PIV measurements on bio-inspired physical MEMS models (Micro-Electronical-Mechanical-Systems), seems to reinforce the performance of the entire canopy and might explain its high density. Our work shows that the transient nature of the signal, with its unique signature in time-frequency domain, is key to the understanding of the presence of so many hairs. The long-held assumption that the working of an integrated sensory system could be understood using continuous sine waves on single sensors was proven to be a misleading path, whose origin lies in a strictly physiological approach without consideration for the ecology of the animal. Our approach, very much similar to the one heralded by M. Koehl, rests on the unique power of combining field work to identify the appropriate natural selection factors, elaborate measurements in the laboratory using non-contact laser-based methods and a whole suite of computational, analytical and physical models.
