Localizing the Puke Button of Grasshoppers: Tactile Stimulation of Different Body Regions Influences the Regurgitation Response of Schistocerca Serialis Cubense (Orthoptera)

Regurgitation behavior is a defense strategy present in several insect orders where herbivorous prey may acquire secondary noxious metabolites from plants and store them to later orally excrete when threatened. Research on regurgitation has focused on its chemical composition, its relationship with diet, and its noxious effect on predators. However, virtually nothing is known about the proximal mechanisms eliciting this behavior. As regurgitation is expected to be closely connected with the structure and control of the gut, we aimed to determine whether pressure applied to different body regions (head, thorax, hind legs and abdomen) of the grasshopper elicited different responses. We found distinctly different regurgitation responses when stimulating different body regions. Stimulation on thorax triggered regurgitation most frequently, possibly due to the anatomical placement of the neural control of the gut. Additionally, we tested regurgitation responses between different instars and found that regurgitation was less likely to occur in adults than in the 4th and 5th nymphal instars. These findings suggest that the developmental differences between nymphs and adults contribute to the regurgitation behavior. Overall, our results provide a baseline for future research on the physiology behind the control of the regurgitation behavior.