Multisensory integration in the ultrasound-triggered escape response of the praying mantis, Parasphendale agrionina

The praying mantis Parasphendale agrionina possesses two sensory systems that could share responsibility for bat evasion: (1) the auditory system sensitive to the vocalizations insectivorous bats emit (echolocation) while hunting flying insects, and (2) a cercal system sensitive to wind generated by an approaching bat.; Wind puffs activated at least six different wind-sensitive interneurons that carry information from the cerci to the thoracic motor areas. Under simulated flight conditions, weak wind puffs still elicited activity in four wind-sensitive interneurons whose activity also varied with stimulus direction. Cercal stimulation does not evoke terrestrial escape responses, but do evoke hindwing-forewing phase changes during flight. Hot-wire anemometer measurements demonstrate bats can generate enough wind during attacks to elicit these behavioral responses during flight, but implanted electrode recordings of wind-sensitive interneuron activity in mantids during bat attacks indicate only 75 ms between bat detection and capture. This may not provide enough time for the mantis to completely avoid a bat based on wind cues alone, but mantids may alter their flight path enough to cause the bat to mishandle the mantis, dropping instead of capturing it. The wing-beat phase changes could serve this purpose and mediate “last ditch” maneuvers.; Implanted electrode recordings from ultrasound-sensitive interneuron 501-T3 (the interneuron likely responsible for triggering the auditory-mediated evasive response) during flying bat attacks reveal 501-T3 shuts down during the last 300 ms of an attack. An auditory-mediated response will not occur after this shutdown. Behavioral experiments also revealed that bat attack sequences containing rapid transitions from low to high vocalization rates could trigger the mantis evasive response too late, allowing the bat to capture the mantis. In both of these cases, it would benefit the mantis to have a backup system (like the cercal system) to mediate “last-ditch” responses.; Free flight encounters between bats and mantids demonstrate that hearing increases mantis survival by 49% compared to deafened mantids. Deafened mantids with functioning cercal systems did not survive bat attacks better than deafened mantids with deactivated cercal systems.