Sluggish movement and repugnant odor are positively interacting insect defensive traits in encounters with frogs

Sluggish movement is common in chemically defended insects. We have recentl y shown that sluggish movement can be beneficial to prey when it fails to r elease the attack response of an ambush (=motion-oriented) predator. Here, we test the hypothesis that sluggish movement and chemical defense (i.e., r epugnant odor) together are more defensive than either alone. We manipulate d the movement and odor of lubber grasshoppers to produce four prey types: (1) sluggish-moving and high odor, (2) sluggish-moving and low odor, (3) fa st-moving and high odor, and (4) fast-moving and low odor. We then offered these prey to frogs. In two independent experiments, frogs attacked prey ty pe 1 (i.e., sluggish-moving and high-odor prey) significantly later than th ey attacked the other prey types. Hence, the defenses of sluggish movement and repugnant odor can act together to produce a prey that is better defend ed than prey with either defense alone. This may help explain why these two traits commonly cooccur in insects.