Read the two texts carefully and answer the questions that follow each text. Use your own words throughout as far as possible.

In temperate regions, honeybees have to face the problem of surviving through the winter when there is no nectar or pollen to be gathered and  when for days or weeks on end the temperature is below the level at which honeybees are able to fly (10oC Celsius). An important first step for a new colony is the selection of a snug1 shelter. House-hunting is part of swarming, which is the honeybees’ method of establishing a new colony. The founding of a honeybee colony is fraught with danger2. To survive the first winter, the colony must find a good site, build a nest of energy-expensive beeswax combs, rear offspring that  outlive the winter, and gather the necessary food for winter. If a new colony does survive the critical first winter, it will endure on the average for another five years. In short, a colony has the potential to survive for a long time but faces great risks in moving from an old nest to a new one. It is obvious that a swarm cannot rely on trial-and-error5 methods to find a suitable site. Each colony must make a single, careful decision with which it can live for many years.

Swarming may occur in early summer. The old queen and her retinue depart in a mad swirl, pouring out of the nest and beginning a short flight. The swarm travels only a few tens of metres and then settles in a beardlike cluster on some object. usually a branch of a tree or bush. Soon after the swarm has settled, the scout bees fly off in all directions to begin their reconnaissance. Their search extends out to 10 kilometres or more from the old nest. The scouts are the oldest bees in the swarm, the ones that have already foraged for the colony and are thus familiar with the territory. They number a few hundred, or about 5% of the swarm’s population.

The scouts visit many possible cavities. The volume of a cavity is the nest-site property that is perhaps most critical. The swarm requires about 15 litres of space in which to store 10 kg of honey. A scout bee needs about 40 minutes to inspect a nest site. After the initial discovery, the scout continues to visit a good site but the visits apparently become sporadic, each visit perhaps an hour after the preceding one and lasting for less than a minute. The sporadic returns probably enable scouts to check the site quickly under different conditions, such as later in the day when the angle of the sun has changed or after a rainstorm that may have flooded the cavity. When the inspection is finished, a scout has walked 50 metres or more around the inside of the cavity and has covered all its inner surfaces. Evidently scout bees rely primarily on walking about in a prospective nest site to measure its volume and suitability.

Once the scouts have selected the future home, they make zigzag runs (punctuated6 by bursts of wing buzzing) through the swarm, thereby signalling the other bees to break up the cluster. The chains of hanging bees begin to disintegrate. Soon the entire swarm is airborne and forms a cloud about 10 metres in diameter. To pilot the other bees to the new home site, the scouts streak through the swarm in the direction of the site.

When the swarm reaches the nest, the scouts somehow signal it to stop. Then they drop down from the cloud formed by the swarm, alight at the entrance to the nest and release assembly pheromone from a gland in the tip of the abdomen. This is a chemical signal that the bees sense as an odour, and pinpoints the entrance to the nest. Soon the other bees are streaming into the nest cavity to make their new home. Within a few hours, they are cleaning out debris, constructing combs and flying off to forage for nectar and pollen. A new colony has been established.

To add to problems with droughts, floods, and malnutrition, large areas of Africa are bracing themselves for a locust invasion. Locust plagues have been known for thousands of years but until this century they have been something of a mystery1. A cloud of these insects appears as if from nowhere. There are so many that they can cover several hundred square kilometres, turning the sky dark. They fall on the land and eat all vegetation in their path, each insect consuming twice its own weight every day. Everything is covered with locusts: houses, streets, trees, fields, and even people. They are not directly dangerous to human beings, but they strip fields bare in hours. In poorer countries, when a swarm of locusts comes through and eats all the crops, the people may later starve. In due course, the locusts move on and eventually die. Then for some years there is not a sign of locusts in the area.

For many centuries, farmers and scientists wondered what happened to the locusts in between the years when they swept across whole countries in massive numbers. Where did they come from and where did they go to? The answer came when a scientist, Dr Uvarov, pointed out the relationship between the desert grasshopper and the locust, which were previously assumed to be two different species of insect.

The grasshopper lives a solitary life, takes on the colour of the ground around it, has a different body shape, and generally moves around much more slowly than the locust, which gathers in swarms, is coloured black and yellow, and is extremely nervous and active in movement. Dr Uvarov’s surprising discovery was that the two insects were really the same species. Under certain environmental conditions, the solitary grasshopper changes until it becomes the locust.

What happens is this. The grasshopper lives in an arid region. Sometimes there is a lot more rain than usual. Then the desert suddenly produces more vegetation than normal. The grasshopper, which can reproduce very swiftly (each female laying 400 eggs at a time) increases in number since more food is available. Eventually, the weather returns to its normal pattern. The desert vegetation disappears, and the mass of grasshoppers are forced to congregate in a smaller and smaller area to find any food that remains. Under these conditions of extreme overcrowding, the gregarious locus develops.

Next, on a warm day, having consumed most of the available food, the locusts take to the air and fly away, carried by the prevailing winds. If the wind takes them out to sea, or into more desert, they will perish. However, if they reach more vegetation, they devour it and continue to breed and multiply until conditions stimulate them to fly off. This cycle is repeated until eventually lack of food, the weather, or disease destroys them.

To man, the locus always represents a distinct threat. Several international bodies attempt to keep watch on the breeding areas from which locusts originate. When suitable conditions for a locust plague develop, they try to control the danger by spraying the areas with insecticides from the air. If this is done in time, it can be successful, but if the locusts breed and take to the air in large numbers before they are observed, there is little man can do to stop their progress. In such cases, attempts to trap, spray, or poison the insects have in the past proved only partially successful. The sheer volume of locusts is too great. Nothing can be done except to wait for the voracious insects to eat their fill and move away.

Questions

1 What does the word ‘snug’ tell us about a suitable site for a new colony?

2 How is the founding of a honeybee colony ‘fraught with danger’?

3 What is the main reason why the scouts are the oldest bees in a colony?

4 How many bees may there be in an average swarm?

5 What evidence is there that the scouts do not display a ‘trial-and-error’ method to select a new site?

6 Explain what is meant by the word ‘punctuated’ in this context.

7 Which word in the last paragraph shows that the writer is uncertain how the scouts manage to do something important to the swarm?

8 In a paragraph of about 160 words, summarise the role of honeybee scouts in establishing a new colony.

1 Explain which aspects of locust plagues are said to be ‘something of a mystery’ later in the article?

2 How are locusts dangerous to human beings?

3 Why is Dr Uvarov mentioned in this article?

4 Explain what two factors lead to the creation of a swam of locusts.

5 Which word and fact demonstrate that locusts cannot decide in which direction they will fly?

6 What is the aim of the spraying mentioned in this article?

7 What evidence is there in the article that locusts are voracious?

Sample Answers

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