Description of the defensive behaviour of four neotropical harvestmen (Laniatores: Gonyleptidae) against a synchronic and sympatric wolf spider (Araneae: Lycosidae)

Summary Harvestmen have an extensive list of predators, among which spiders stand out. To avoid predation, harvestmen have developed several defensive behaviours, which range from attempting not to be detected by their predator to releasing defensive chemicals. In this work, our aim was to determine which are the defensive behaviours adopted by four synchronic and sympatric species of gonyleptid harvestmen (Acanthopachylus aculeatus; Pachyloides thorellii, Discocyrtus prospicuus and Parampheres bimaculatus) when attacked by the lycosid Schizocosa malitiosa, a wolf spider abundant in Uruguay. Schizocosa malitiosa attacked the four harvestmen species on 77% of observations, but was only able to predate on a low percentage of cases, when the females were more effective than their male counterparts. Unexpectedly, post-detection behaviours were more effective than chemicals, which in no case prevented predation or ingestion of the prey, while the thick cuticle is a very effective barrier against this spider.