Ability makes a thief: vision, learning, and swift escape help kleptoparasitic hover wasps not to fall prey to their spider hosts

Abstract

Stealing prey items from other animals entails obvious benefits for the thief. However, this so-called kleptoparasitic behavior can also involve costs including injury or even death, especially when stealing from a potential predator. Here, we examined how kleptoparasitic hover wasps (Parischnogaster sp.) that steal prey items out of spider webs handle the risk of falling prey to their hosts. We tested the wasps’ ability to evade different webs under natural and experimental conditions and whether webs are perceived visually. Further, we tested whether wasps learn about web position and are able to avoid them in future trajectories as well as how quick wasps escape from webs once entangled. Additionally, we recorded the attack time for different spider species towards prey items placed into their webs, to estimate the risk of being attacked when entangled. Our results provide strong support for visual web perception by wasps facilitating the successful evasion of webs in flight trajectories, learning capability, and quick escape from webs once entangled. At the same time, the results, together with our observations in the field, suggest a specialization of kleptoparasitizing spider webs with overall lower risk of predation. Stealing prey from other predators often entails significant risk of injury and death. Yet, most research on such kleptoparasitism focused on the benefits to the kleptoparasite or the cost to the host, thereby overlooking an important component to explain the evolution and maintenance of kleptoparasitism. Here, we examine the potential costs for hover wasps when stealing prey from spider webs and test how wasps reduce the potential risks of this kleptoparasitic foraging behavior. While often described from casual observations, kleptoparasitism in hover wasps is so far unstudied. We show that kleptoparasitism from spider webs is associated with costs for hover wasps, but that visual detection of webs, avoidance learning, and rapid escape behavior mitigate those costs. Our study hints at hover wasps targeting certain host species where their mitigating strategies are most effective.