Assassin Bugs

An article at the BBC discusses research that some biologists have done on a kind of insect called an Assassin bug. These creatures exhibit a fascinating behavior as explained in the article:

Assassin bugs hunt spiders on their webs by stalking or luring their victims before stabbing them with their long, sharp snouts. Researchers studying these aggressive arthropods have now found that they use noise to cover their tracks. The bugs wait for the wind to rustle the web, then take the opportunity to sneak up on their prey.

"Web-building spiders have only rudimentary eyesight, so avoiding being seen is not an issue for web-invading arthropods," the team explained in the paper. "The main sensory system of web-building spiders is based on interpreting vibrations in the web - web silk is exquisitely proficient at transmitting vibrations from potential prey and predators in the web."

The researchers placed the bugs onto the spider webs and used a desk fan to simulate a breeze on the web. When the fan was on, "the assassin bugs stepped more often and walked in a more continuous manner", the team explained. They described this tactic as "opportunistic smokescreen behaviour".

"The exciting thing in this study is that the assassin bugs can increase their chances of catching food by using wind noise as cover." The breeze did not seem to trigger the assassin bug to move when it was in an unoccupied spider web. This, the team wrote, suggested that "noise-related timing of behaviour reflects decisions made as part of a predatory strategy", rather than just a response to the physical movement of the web.

Assassin bugs also have a strange way of moving, and the scientists think this bouncing gait - "gently erratically rocking in the web" - may make it more difficult for the spiders to identify the characteristic vibrations of footsteps on silk. The bugs are perhaps "simulating debris moving in the wind", explained the researchers.

In a previous study the same team discovered that the bugs lured spiders by "pretending" to be prey tangled in the web. They tapped the silk to mimic the vibrations of a trapped insect. When the spider approaches - or when the assassin bug gets within striking distance - the predator strikes with its tube-like mouthparts, through which it injects the victim with a toxin that liquefies its insides so they can be sucked out.

Sometimes I'm just in awe of the miracles that natural selection coupled with accidental genetic mutations can accomplish purely by blind dumb luck. I know it takes a lot of faith to believe that such marvels can happen by chance, but it must be true else the scientific whizzes who host talk shows at MSNBC wouldn't make fun of Rick Perry and Michele Bachmann for not believing it.