Soal Latihan dan Jawaban Reading Comprehension 18
Many ants forage across the countryside in large numbers and undertake mass
migrations; these activities proceed because one ant lays a trail on the ground for the others
to follow. As a worker ant returns home after finding a source of food, it marks the route
by intermittently touching its stinger to the ground and depositing a tiny amount of trail
(5) pheromone – a mixture of chemicals that delivers diverse messages as the context
changes. These trails incorporate no directional information and may be followed by other ants
in either direction.
Unlike some other messages, such as the one arising from a dead ant, a food trail has to
be kept secret from members of other species. It is not surprising then that ant species use
(10) a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to
these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana
calculated that one milligram of this substance would suffice to lead a column of ants three
times around Earth.
The vapor of the evaporating pheromone over the trail guides an ant along the way,
(15) and the ant detects this signal with receptors in its antennae. A trail pheromone will
evaporate to furnish the highest concentration of vapor right over the trail, in what is called a
vapor space. In following the trail, the ant moves to the right and left, oscillating from side
to side across the line of the trail itself, bringing first one and then the other antenna into
the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space.
(20) The signal it receives causes it to swing to the left, and the ant then pursues this new
course until its right antenna reaches the vapor space. It then swings back to the right, and so
weaves back and forth down the trail.
Reading Comprehension 18
The mass migration of ants
The information contained in pheromones
Different species of ants around the world
How ants mark and follow a chemical trail
search for food
To indicate how far away the food is
To protect their trail from other species
To attract different types of ants
To reduce their sensitivity to some chemicals
a type of ant that is common in many parts of the world
the different types of pheromones ants can produce
that certain ants can produce up to one milligram of pheromone
how little pheromone is needed to mark a trail
They sense the vapor through their antennae.
They avoid the vapor spaces by moving in a straight line.
They follow an ant who is familiar with the trail
They concentrate on the smell of food.
in the source of food
in the receptors of the ants
just above the trail
under the soil along the trail