Assassin (暗杀者) bugs live up to their name. The insects expertly hunt and feed upon other small invertebrates (无脊椎动物), giving them a poisonous bite. Some species even hunt spiders and use a strange trick to gain the upper hand.
Using their antennae (触须), assassin bugs tap spiders, which appears to confuse them long enough to let the bugs make a poisonous strike, researchers reported on September 29. The findings provide insight into some of the complex hunting tactics that predators (捕食性动物) evolve when targeting dangerous prey (猎物) .
Assassin bugs spend their lives in a place most insects avoid: spider webs. The bugs silently creep along the spider’s silk, taking care to make their movements seem harmless before violently killing the web’s architect, seizing the spiders with their front legs and injecting them with poison.
While watching two species of assassin bugs hunt spiders, ecologists Anne Wignall and Fernando Soley took note of the bugs’ habit of lightly knocking their antennae on spiders once the bugs were within striking distance.
“It struck us early on that tapping prey was a really strange thing to do,” says Wignall. Spiders could easily defend themselves and kill the bugs. “Watching the bugs spend so much time and effort on avoiding detection, only to practically tap the spiders on the shoulder was absolutely fascinating.”
To figure out why the bugs tap, Wignall and Soley tested the behavior of 30 spiders in the laboratory. The researchers copied the bugs’ antennae tapping by gently brushing the spiders’ leg with a dog hair. After the tapping, the team measured the spiders’ responses to movements on the web, copying a struggling insect.
Tapped spiders were far less aggressive than those that weren’t tapped, fully ignoring the movements four times as often. Tapped spiders also attacked about 25 percent as often as their untapped counterparts.
Wignall thinks that the assassin bugs are reducing spiders’ aggression levels by imitating the types of physical touch that these typically solitary (独处的) spiders experience near fellow spiders. “Whenever they do come across another spider, it’s usually because it’s a close relative in the nest, or a potential mate. Both of which are situations in which aggression would not be a good idea,” she says.
Zoologist Ondřej Michálek, who was not involved with the study, says that the researchers have a “completely valid theory.” Many spiders avoid cannibalism (同类相食) by using special touch signals that could be copied by skilful predators, thus tricking the spiders, he says.
【小题1】What is unusual about assassin bugs?| A．Their bite is poisonous. | B．Their movements make little noise. |
| C．They don’t avoid spiders’ webs. | D．They kill their prey violently. |
| A．They used a great deal of time and effort. | B．They were able to defend themselves. |
| C．They deliberately touched the spiders. | D．They were able to kill the spiders. |
| A．They are keen on physical touch. | B．They are pretending to be spiders. |
| C．They are usually solitary. | D．They are looking for a mate. |
| A．Why animals use complex hunting tactics. | B．Why assassin bugs tap their prey. |
| C．Assassin bugs have a poisonous bite. | D．Assassin bugs-a dangerous predator. |
