The Subgenual Organ Complex in Stick Insects: Functional Morphology and Mechanical Coupling of a Complex Mechanosensory Organ

Leg chordotonal organs in insects show different adaptations to detect body movements, substrate vibrations, or airborne sound. In the proximal tibia of stick occur two organs: subgenual organ, a highly sensitive vibration receptor and distal which function is yet unknown. The organ consists linear set scolopidial sensilla extending direction toward tarsus. Similar elaborate hearing crickets bushcrickets, where auditory are closely associated with thin tympanal membranes trachea leg. Here, we document position attachment points for three species without ( Ramulus artemis , Sipyloidea sipylus Carausius morosus ). located dorsal hemolymph channel attaches at end posterior leg cuticle by tissue strands. central part placed closer suspended fine anterior clearly separated from tracheae, while over trachea. not connected tendon muscle, would indicate proprioceptive function. have dendrites oriented This morphology does reveal obvious as organs, responses forces longitudinal leg, likely vibrational stimuli transmitted leg’s hemolymph. evolutionary convergence complex sets between atympanate emphasized functional morphologies sensory specializations.