even neighboring sensilla may have very different sensitivities to strain depending on their orientation in the cuticle. For example, stick insects possess two groups of campaniform sensilla on the dorsal side of their legs' trochanter whose short axes are oriented perpendicularly to one another (see inset in leg schematic). As a result, one group (G3) responds when the leg is bent upwards, whereas the other group (G4) responds when the leg is bent downwards. Round campaniform sensilla can be sensitive in all directions or show directional sensitivity if the cap is asymmetrically coupled with the surrounding collar. The activity of campaniform sensilla may be slowly-adapting (tonic), signaling the magnitude of cuticular deformation, and/or rapidly adapting (phasic), signaling the rate of cuticular deformation. Based on their responses to white noise stimuli, campaniform sensilla may also be described more generally as signaling two features that approximate the derivative of each other. In addition, activity adapts to constant loads and shows hysteresis (history dependence) in response to cyclic loading. Campaniform sensilla project directly to motor neurons and to various interneurons, which integrate their signals with signals from other proprioceptors. In this way, campaniform sensilla activity can affect the magnitude and timing of muscle contractions. Function of leg campaniform sensilla Campaniform sensilla on the legs are activated during standing and walking. Their sensory feedback is thought to reinforce muscle activity during the stance phase and to contribute to inter-leg coordination, much like sensory feedback from mammalian Golgi tendon organs. Feedback from leg campaniform sensilla is also important for the control of kicking and jumping. Function of wing and haltere campaniform sensilla Campaniform sensilla on the wings and halteres are activated as these structures oscillate back and forth during flight, with the phase of activation depending on the placement of the sensilla. The campaniform sensilla on the wing encode the wing's aerodynamic and inertial forces, whereas sensilla on the base of the haltere are thought to encode Coriolis forces induced by body rotation during flight, allowing the structure to function as a gyroscope. Feedback from wing and haltere campaniform sensilla is thought to mediate compensatory reflexes to maintain equilibrium during flight. Computational models To better understand the function of campaniform sensilla, computational models that mimic their response properties are being developed for use in simulations and robotics. References Insect anatomy Sensory receptors es:Sensilia fr:Sensille ru:Сенсиллы членистоногих