Defensive Responses of Neotropical Harvestmen (Arachnida, Opiliones) to Generalist Invertebrate Predators

Descriptions of defensive behaviors used by Neotropical harvestmen are rarely based upon direct observations of encounters between individuals and syntopic predators. In this study, we investigated the defensive responses exhibited by five harvestman species from Costa Rica in interactions with ctenid spiders (Cupiennius spp.), whip spiders (Phrynus pseudoparvulus), onychophorans (Epiperipatus sp.), and centipedes (Scolopendra sp.). We also observed interactions between harvestmen and a non-predatory invertebrate, the millipede Nyssodesmus python. In 64 encounters, ctenid spiders consumed 11 harvestmen, including eight Prionostemma sp., two Cynorta marginalis, and one Eupoecilaema magnum. The most frequent defensive behavior exhibited by harvestmen was fleeing. Other behaviors included aggression (striking with leg II), bobbing, leg autotomy, lying flat, and thanatosis. Prionostemma exhibited the most variable responses, especially in the presence of ctenid spiders. In addition to the lab-based e...