What’s the News: Among the many creepy denizens of Australia—such as the red back spider, seen here hauling a lizard into its nest, and the saltwater crocodile, which kills with its distinctive “death roll”—the assassin bug is right at home. With its erratic, long-legged walk, it stalks along spiders’ webs, caressing its prey with its antennae and then stabbing them with its beak. Now, scientists who spy on these spider-eaters report that the bugs have yet another charming behavior in their toolkit: using the breeze as cover when they go in for the kill.
How the Heck:
- The team had spiders of species known to be assassin-bug bait construct their webs in wooden frames. Then, they turned a desk fan on the hapless arthropods to simulate wind and placed an assassin bug on each web.
- The bugs, which normally have an extremely irregular gait that mimics random vibrations in the web and thus helps them escape spiders’ attention, walked more smoothly and quickly toward their prey when the fan was on. They also caught spiders more frequently when there was a breeze.
- The bugs didn’t engage in this smooth-stepping behavior when the fan was on but the web was empty, suggesting that it really is a predatory maneuver, not just a generic reaction to wind.
What’s the Context:
- Taking advantage of a prey’s distraction has been observed before in other spider-hunters: one jumping spider from Queensland waits until its prey is busy wrapping up a hapless fly, then leaps in for the kill.
- That species and several others also speed up the hunting process under the cover of wind, according to a 1996 paper by several of the researchers on the assassin bug-study.
- Assassin bugs also mimic the vibrations made by a struggling insect caught in a web, drawing the spider near and then liquefying its guts with a toxin and sucking them out. That was another discovery made by this team, with its impressive appetite for the strange and somewhat revolting.
Reference: Wignall et al. Exploitation of environmental noise by an araneophagic assassin bug. Animal Behaviour. doi:10.1016/j.anbehav.2011.07.038