《考研英語(yǔ)閱讀理解100篇 高分版》 Unit 17 - TEXT FOUR

The humble but industrious ant has long served as a metaphor for the economic virtues of simplicity, parsimony and diligence. But in the case of weaver ants in Africa, this description may be more than just a metaphor. According to Paul Van Mele of the Consultative Group on International Agricultural Research and his colleagues, African mango farmers could increase their harvests by as much as two-thirds with the help of these doughty insects.
Mangoes in Africa, as elsewhere, often fall prey to fruit flies, which destroy about 40% of the continent's crop. In fact, fruit flies are so common in African mangoes that America has banned their import altogether, to protect its own orchards. African farmers, meanwhile, have few practical means to defend their fruit. Chemical pesticides are expensive. And even for those who can afford them they are not that effective since, by the time a farmer spots an infestation, it is too late to spray. Added to that, spraying tall trees is a much more complicated and unhealthy business than treating low-growing fruit and vegetables.
Agricultural scientists have also looked at controlling fruit flies with parasitic wasps. But the most common ones kill off only about one fly in 20, leaving plenty of survivors to go on the rampage. Lethal traps baited with fly-attracting pheromones are another option. But they, too, are expensive. Moreover, all these methods require farmers to detect the presence of fruit flies, and to identify them as the main threat to their crop—no mean feat when most of the action is taking place in dense, leafy canopies ten metres off the ground. Instead, most farmers simply harvest their fruit early, when it is not yet fully ripe. This makes it less vulnerable to the flies, but also less valuable.
Farmers whose trees are teeming with weaver ants, however, do not need to bother with any of this. In a survey of several orchards in Benin, Dr. Van Mele and his colleagues found an average of less than one fruit-fly pupa in each batch of 30 mangoes from trees where weaver ants were abundant, but an average of 77 pupae in batches from trees without weaver ants. The weaver ants, it turns out, are very thorough about hunting down and eating fruit flies, as well as a host of other pests. The only drawback is the ants' painful bite, which can be avoided by harvesting fruit with poles, rather than climbing trees.
Weaver ants have been used for pest control in China and other Asian countries for centuries. The practice has also been adopted in Australia. But Dr. Van Mele argues that it is particularly suited to Africa since weaver ants are endemic to the mango-growing regions of the continent, and little training or capital is needed to put them to work. All you need do is to locate a suitable nest and run strings from it to the trees you wish to protect. The ants will then quickly find their way to the target. Teaching a group of farmers in Burkina Faso to use weaver ants in this way took just a day. Those farmers no longer use pesticides to control fruit flies, and so are able to market their mangoes as organic to eager European consumers, vastly increasing their income. The ants, so to speak, are on the march.
1. For weaver ants in Africa, the description of the economic virtues of ant is more than just a metaphor because _____.
[A] the weaver ants could really bring out economic benefits for the fruit farmers
[B] the weaver ants are really economical and diligent in killing the fruit flies
[C] the weaver ants are in fact have the economic virtues
[D] the weaver ants are not a typical representative for the economic virtues
2. The word “infestation” (Line 5, Paragraph 2) most probably means _____.
[A] pest
[B] infection
[C] invasion
[D] aggression
3. The method of using chemical pesticide is not practical to defend the African farmers' fruit because of the following reasons except that _____.
[A] the cost of using chemical pesticide is too high for most of the farmers in Africa
[B] the chemical pesticide is not so effective in killing the fruit pests
[C] it is hard to decide a best change of spraying the chemical pesticide with most efficiency
[D] it requires special technique to spray tall trees with chemical pesticide
4. Reaping the fruit too early is not a good way to deal with the fruit flies because _____.
[A] the fruit will be less welcomed in the market given its lack of ripeness
[B] the fruit will be of worse taste and thus of much less value
[C] the fruit becomes less vulnerable to the fruit flies
[D] the fruit will still be affected by the flies even after they are harvested
5. Dr. Van Mele argues that weaver ants are particularly suited to Africa because of the following reasons except that _____.
[A] weaver ants are prevalent in the mango-growing regions in Africa
[B] the cost of employing weaver ants is low
[C] it is easy to grasp the method of using the weaver ants
[D] it requires simple training to make the weaver ants work