It is like a scene from a horror film: a spider web is several meters wide, which is home to thousands of spiders. And that was what Jason G. Goldman, an animal behavior researcher, found along a muddy path in the Peruvian Amazon jungle—the web arched from tree to tree, a structure containing too many spiders to count. They appeared to function as a society, just like ants or bees.
Anelosimus eximius, the species Goldman met in the rainforest, is not the only kind of social spiders in the world, but it does construct the biggest webs. Some can reach more than 7.6m long and 1.5m wide. A web of that size could contain as many as 50,000 individual spiders.
Anelosimus eximius was first discovered more than a century ago by a French scientist named Eugene Simon. More social spiders have been discovered since. One was found as recently as 2006.
An Anelosimus eximius colony(群体) contains adult males and females as well as youngsters, but the majority of spiders on the web are females. Males account for only between 5% and 22% of any colony's population. Social spiders work together to build, maintain and clean their webs. They work together to catch prey(猎物), and dine together when they trap a large feast. The females work together to care for the young in the colony. They feed their youngsters by vomiting(吐出) up food for them, just like mother birds.
Why did these spiders become social? Researchers have discovered three ecological(生态的) elements that often lead to cooperative(合作的) living among spiders.
Social spiders tend to feed on bigger prey, for one thing. Spiders living in places where it is difficult to hunt large or more profitable prey alone may eventually figure out that it is in their interest to work together.
B . 
C . 
D . 
