Oscillations for active sensing in olfaction: bioinspiration from insect antennal movements.

Crustacean and insect antennal scanning movements have been postulated to increase odorant capture but the exact mechanisms as well as measures of efficiency are wanting. The aim of this work is to test the hypothesis that an increase in oscillation frequency of a simplified insect antenna model translates to an increase of odorant capture, and to quantify by how much and through which mechanism. We approximate the antennal movements of bumblebees, quantified in a previous study, by a vertical oscillatory movement of a cylinder in a homogeneous horizontal flow with odorants.

Insect pectinate antennae maximize odor capture efficiency at intermediate flight speeds.

Flying insects are known to orient themselves over large distances using minute amounts of odors. Some bear pectinate antennae of remarkable architecture thought to improve olfactory performance. The semiporous, multiscale nature of these antennae influences how odor molecules reach their surface.

The morphological heterogeneity of cricket flow-sensing hairs conveys the complex flow signature of predator attacks.

Arthropod flow-sensing hair length ranges over more than an order of magnitude, from 0.1 to 5 mm. Previous studies repeatedly identified the longest hairs as the most sensitive, but recent studies identified the shortest hairs as the most responsive.

Predator-induced flow disturbances alert prey, from the onset of an attack.

Many prey species, from soil arthropods to fish, perceive the approach of predators, allowing them to escape just in time. Thus, prey capture is as important to predators as prey finding. We extend an existing framework for understanding the conjoint trajectories of predator and prey after encounters, by estimating the ratio of predator attack and prey danger perception distances, and apply it to wolf spiders attacking wood crickets.

Directional cues in Drosophila melanogaster audition: structure of acoustic flow and inter-antennal velocity differences.

Drosophila melanogaster have bilateral antisymmetric antennae that receive the particle velocity component of an acoustic stimulus. Acoustic communication is important in their courtship, which takes place in the acoustic near-field. Here, the small size of the dipole sound source (the male wing) and the rapid attenuation rate of particle velocity produce a spatially divergent sound field with highly variable magnitude.

Responses of cricket cercal interneurons to realistic naturalistic stimuli in the field.

The ability of the insect cercal system to detect approaching predators has been studied extensively in the laboratory and in the field. Some previous studies have assessed the extent to which sensory noise affects the operational characteristics of the cercal system, but these studies have only been carried out in laboratory settings using white noise stimuli of unrealistic nature. Using a piston mimicking the natural airflow of an approaching predator, we recorded the neural activity through the abdominal connectives from the terminal abdominal ganglion of freely moving wood crickets (Nemobius sylvestris) in a semi-field situation.

Air motion sensing hairs of arthropods detect high frequencies at near-maximal mechanical efficiency.

Using measurements based on particle image velocimetry in combination with a novel compact theoretical framework to describe hair mechanics, we found that spider and cricket air motion sensing hairs work close to the physical limit of sensitivity and energy transmission in a broad range of relatively high frequencies. In this range, the hairs closely follow the motion of the incoming flow because a minimum of energy is dissipated by forces acting in their basal articulation. This frequency band is located beyond the frequency at which the angular displacement of the hair is maximum which is between about 40 and 600 Hz, depending on hair length (Barth et al.

Why do insects have such a high density of flow-sensing hairs? Insights from the hydromechanics of biomimetic MEMS sensors.

Insects and arachnids are often quite hairy. The reasons for this high density of sensory hairs are unknown. Previous studies have predicted strong hydrodynamic coupling between densely packed airflow-sensitive hairs.

Relative contributions of organ shape and receptor arrangement to the design of cricket's cercal system.

Understanding the relative contributions of the shape of a sensory organ and the arrangement of receptors to the overall performance of the organ has long been a challenge for sensory biologists. We tackled this issue using the wind-sensing system of crickets, the cerci, two conical abdominal appendages covered with arrays of filiform hairs. Scanning electron microscopy coupled with 3D reconstruction methods were used for mapping of all cercal filiform hairs.

The aerodynamic signature of running spiders.

Many predators display two foraging modes, an ambush strategy and a cruising mode. These foraging strategies have been classically studied in energetic, biomechanical and ecological terms, without considering the role of signals produced by predators and perceived by prey. Wolf spiders are a typical example; they hunt in leaf litter either using an ambush strategy or by moving at high speed, taking over unwary prey.