Ploys and counterploys of assassin bugs and their dangerous spider prey

Abstract

Behavioural interplay between predator and prey is often overlooked in favour of simpler, more tractable, analyses that focus on just one of the participants. However, a deeper understanding of predator-prey systems can be gained by focusing on the interdependence of predator and prey behaviour, which may be especially complex when the prey has means of retaliation. Web-building spiders are formidable predators of insects, with fangs and venom as weapons, and webs that function both as traps and in transmitting vibrations from intruder movements. Nevertheless, Stenolemus giraffa assassin bugs specialise in preying on web-building spiders using a strategy based on stealth. We illustrate the challenges of pursuing dangerous prey through detailed observations of S. giraffa in pursuit of three spider species. We show that it is difficult for S. giraffa to approach spiders without triggering any response from prey spiders, and that they inhibit escalated responses from the spiders by adjusting their behaviour according to the spider’s initial response. The webs of spiders pursued by S. giraffa vary in structure and adhesiveness, and spiders themselves vary in how they respond to disturbances in their webs, creating diverse predatory scenarios. Despite diversity in web type and prey response, S. giraffa was similarly successful at capturing three spider species investigated here, indicating an ability to effectively monitor prey behaviour and adjust their own behaviour to meet the demands of different predatory scenarios.