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  3. Spiders are known for many things. Sociability is not one of them. Most spiders are more likely to try to eat their neighbours t

Spiders are known for many things. Sociability is not one of them. Most spiders are more likely to try to eat their neighbours t

admin2017-03-01  69
问题     Spiders are known for many things. Sociability is not one of them. Most spiders are more likely to try to eat their neighbours than befriend them. Given that there are at least 43,678 species of spiders, though, it is not too surprising that a few have overcome their natural bad-temper and teamed up to form societies. So far, about two dozen such social spiders have been identified. And among them, something really strange has just been found. For one type of spider society turns out to involve two different but closely related species. It is as though anthropologists (人类学家)had discovered villages populated both by human beings and chimpanzees.
    This was discovered by a team led by Lena Grinsted of Aarhus University in Denmark. They were studying a social species of spider called Chikunia nigra, living near Beratan Lake in Bali. Later, as they looked in more detail at their samples, they realised its genes showed that it was actually two species.
    It is not clear why the spiders are social. They do not hunt together. One explanation may be that the colony is acting like a huge kindergarten.
    Ms. Grinsted discovered this possibility by experiment. First, she identified 19 females who were looking after those who were recently born, and another 20 who had eggs. In each case she introduced a new comer, in the form of a spider from the same colony. Both mothers and mothers-to-be were surprisingly tolerant of what would, in most spider species, be a serious threat. Only 40% of the time did they attempt to chase the intruder away, or bite it.
    Ms. Grinsted then took another 40 spiders and replaced some of their little spiders. The result, she found, was that a female was as likely to look after and protect another’s young spider as she was her own.
    Which is interesting, but not all that extraordinary in social groups which are composed of closely related individuals. Except that Ms. Grinsted now knows that this cannot always be the case for her spiders, since two different species are involved. The species in question are pretty similar, which would seem to exclude another common cause of co-action; different spiders do different work in the group.
    Because Ms. Grinsted did not know at the time of her experiment that two species were involved, she cannot be sure how many of the newly-born spiders she interfered were cross-specific. The two species seem more or less equal in number, so chances are it was about half of them. If colony members are acting as foster mothers in the wild, something most odd is going on. Altruism(利他) is not a concept often associated with spiders. Xenophilic(种族间的) altruism is truly strange.
What is the best title for this passage?
选项 A、Sociability of Spiders
B、A Strange Example of Co-operative Behaviour in Spiders
C、Female Spiders and Their Colony
D、Across-species Spiders
答案B
解析 本题为主旨大意题。本文第一段提出大多数蜘蛛缺乏社会性，但为数不多的蜘蛛也结群而居，在这之中还发现一种蜘蛛群体中有两种不同而相近的蜘蛛共存。从第二段开始具体介绍科学家所做的研究及实验结果，在文章最后，作者提出两个奇怪之处，一是蜘蛛的利他性，二是蜘蛛的种间利他主义。选项B概括了奇怪、蜘蛛、合作行为，与本文的阐述一致。
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