Insect Senses

Insects have a variety of ways to sense the world. Although some insects are eyeless, most of them have a pair of compound eyes. If you examine a compound eye with a hand lens, you can see that it is an aggregate of many transparent hexagonal lenses. The light that passes through each lens stimulates a light-sensitive element beneath it. Thus, unlike the eye of a bird or a human, in which a single lens focuses the image onto the retina, the eye of an insect is, true to its name, a compound of many separate visual units, each a light-sensitive structure provided with its own lens. Compound eyes are less adept than our own eyes or birds’ eyes at resolving form and detail, but they are far quicker to perceive movement. (Just think how difficult it is to snatch a fly with your hand.) The ability of compound eyes to resolve detail does, however; increase with the number of visual units that they contain. The wingless and largely inactive female of a firefly has only 600 visual units in her compound eyes, but the winged male, which must find the female by visual means, has 5,000 in his eyes. Dragonflies, which require great visual acuity because they catch their often tiny insect prey while flying, may have a total of 56,000.

Insects, like birds and humans, see colors—not surprising since so many of them are attracted to flowers with bright colors, especially yellow and blue. Although butterflies, like hummingbirds, are attracted to red flowers, most other insects do not see as far into the red range as do we and most birds, but unlike us and like some birds, they see into the near ultraviolet range. Not surprisingly, some flowers have markings that are visible only in the ultraviolet range and that often act as “nectar guides” indicating where the nectar is.

Many insects, especially winged species, also have two or three “simple eyes” that lie between or above the compound eyes. Each simple eye, or ocellus (pl. ocelli), consists of a single large lens with a cluster of light-sensitive elements behind it. The simple eyes are not well adapted for resolving images. Although those of some insects can form an image, it is focused far behind the light-sensitive elements and is thus badly out of focus. The simple eyes, however, are more sensitive to light, especially dim light, than are the compound eyes, and it seems certain that they help regulate the activity rhythms of some insects whose behaviors is at least partly governed by the daily cycle of light and dark.

Almost all insects, both adult and immature forms, have a pair of antennae on the head. Depending upon the species of insect, the antennae are responsible for one or more sensory functions: touch, taste, smell, sound reception, moisture sensing, and temperature assessment. The antennae are often long, threadlike, and many-segmented, but in quite a number of insects their form is greatly modified to facilitate particular sensory functions. The short, three-segmented antennae of blow flies, house flies, and related species function as wind-speed indicators. The bulbous third (last or terminal) segment bears a featherlike projection that catches the wind like a sail and thus causes the entire segment to twist. The central nervous system translates the degree of twist into wind speed or the air speed of a flying individual.

In some other insects, notably saturniid moths, the antennae of the males are greatly enlarged and featherlike in order to accommodate an enormous number of odor receptors. The males use these to perceive an airborne sex-attractant pheromone, a chemical signal that is emitted by the females of their species. When a male smells this pheromone, he flies upwind, often for a considerable distance, until he finds the female. Male mosquitoes also use their antennae in locating females, but in their case the bushy antennae function as sound receptors that are set to vibrating by the sound waves, perceptible to us as a humming tone, that are produced by the beating wings of a female. Unmated male mosquitoes confined in a cage without females are excited by a tuning fork that vibrates at about the same pitch as do the wings of flying female mosquitoes.

 

 

1

Insects have a variety of ways to sense the world. Although some insects are eyeless, most of them have a pair of compound eyes. If you examine a compound eye with a hand lens, you can see that it is an aggregate of many transparent hexagonal lenses. The light that passes through each lens stimulates a light-sensitive element beneath it. Thus, unlike the eye of a bird or a human, in which a single lens focuses the image onto the retina, the eye of an insect is, true to its name, a compound of many separate visual units, each a light-sensitive structure provided with its own lens. Compound eyes are less adept than our own eyes or birds’ eyes at resolving form and detail, but they are far quicker to perceive movement. (Just think how difficult it is to snatch a fly with your hand.) The ability of compound eyes to resolve detail does, however; increase with the number of visual units that they contain. The wingless and largely inactive female of a firefly has only 600 visual units in her compound eyes, but the winged male, which must find the female by visual means, has 5,000 in his eyes. Dragonflies, which require great visual acuity because they catch their often tiny insect prey while flying, may have a total of 56,000.

The word “aggregate” in the passage is closest in meaning to

Acollection

Bpart

Cgrowth

Dinstrument

 

2

Insects have a variety of ways to sense the world. Although some insects are eyeless, most of them have a pair of compound eyes. If you examine a compound eye with a hand lens, you can see that it is an aggregate of many transparent hexagonal lenses. The light that passes through each lens stimulates a light-sensitive element beneath it. Thus, unlike the eye of a bird or a human, in which a single lens focuses the image onto the retina, the eye of an insect is, true to its name, a compound of many separate visual units, each a light-sensitive structure provided with its own lens. Compound eyes are less adept than our own eyes or birds’ eyes at resolving form and detail, but they are far quicker to perceive movement. (Just think how difficult it is to snatch a fly with your hand.) The ability of compound eyes to resolve detail does, however; increase with the number of visual units that they contain. The wingless and largely inactive female of a firefly has only 600 visual units in her compound eyes, but the winged male, which must find the female by visual means, has 5,000 in his eyes. Dragonflies, which require great visual acuity because they catch their often tiny insect prey while flying, may have a total of 56,000.

According to paragraph 1, compound eyes are particularly good for

Aperceiving slight changes in light

Bresolving form and detail

Cproviding a broad field of vision

Ddetecting motion

 

3

Insects, like birds and humans, see colors—not surprising since so many of them are attracted to flowers with bright colors, especially yellow and blue. Although butterflies, like hummingbirds, are attracted to red flowers, most other insects do not see as far into the red range as do we and most birds, but unlike us and like some birds, they see into the near ultraviolet range. Not surprisingly, some flowers have markings that are visible only in the ultraviolet range and that often act as “nectar guides” indicating where the nectar is.

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

AButterflies and hummingbirds are attracted to red flowers, but most other birds and insects prefer a range of different colors.

BAside from butterflies, few insects can see red well, but most insects can see colors in the near ultraviolet range.

CWith some exceptions, humans are more like birds than like insects in terms of the way they see colors.

DHumans and birds are generally able to see more shades of color than most insects can.

 

4

Many insects, especially winged species, also have two or three “simple eyes” that lie between or above the compound eyes. Each simple eye, or ocellus (pl. ocelli), consists of a single large lens with a cluster of light-sensitive elements behind it. The simple eyes are not well adapted for resolving images. Although those of some insects can form an image, it is focused far behind the light-sensitive elements and is thus badly out of focus. The simple eyes, however, are more sensitive to light, especially dim light, than are the compound eyes, and it seems certain that they help regulate the activity rhythms of some insects whose behaviors is at least partly governed by the daily cycle of light and dark.

The word “cluster” in the passage is closest in meaning to

Alayer

Bpresence

Csystem

Dgroup

 

5

Many insects, especially winged species, also have two or three “simple eyes” that lie between or above the compound eyes. Each simple eye, or ocellus (pl. ocelli), consists of a single large lens with a cluster of light-sensitive elements behind it. The simple eyes are not well adapted for resolving images. Although those of some insects can form an image, it is focused far behind the light-sensitive elements and is thus badly out of focus. The simple eyes, however, are more sensitive to light, especially dim light, than are the compound eyes, and it seems certain that they help regulate the activity rhythms of some insects whose behaviors is at least partly governed by the daily cycle of light and dark.

According to paragraph 3, which of the following does NOT describe simple eyes?

AThey are made up of a number of light-sensitive elements and one lens.

BThey occur in insects that lack compound eyes.

CThey cannot form clear images.

DThey can easily detect dim light.

 

6

Almost all insects, both adult and immature forms, have a pair of antennae on the head. Depending upon the species of insect, the antennae are responsible for one or more sensory functions: touch, taste, smell, sound reception, moisture sensing, and temperature assessment. The antennae are often long, threadlike, and many-segmented, but in quite a number of insects their form is greatly modified to facilitate particular sensory functions. The short, three-segmented antennae of blow flies, house flies, and related species function as wind-speed indicators. The bulbous third (last or terminal) segment bears a featherlike projection that catches the wind like a sail and thus causes the entire segment to twist. The central nervous system translates the degree of twist into wind speed or the air speed of a flying individual.

When the author says that the antennae of insects are “many-segmented”, he means that they

Ahave a variety of functions

Bare capable of a range of movements

Care responsive to touch

Dare divided into several parts

 

7

Almost all insects, both adult and immature forms, have a pair of antennae on the head. Depending upon the species of insect, the antennae are responsible for one or more sensory functions: touch, taste, smell, sound reception, moisture sensing, and temperature assessment. The antennae are often long, threadlike, and many-segmented, but in quite a number of insects their form is greatly modified to facilitate particular sensory functions. The short, three-segmented antennae of blow flies, house flies, and related species function as wind-speed indicators. The bulbous third (last or terminal) segment bears a featherlike projection that catches the wind like a sail and thus causes the entire segment to twist. The central nervous system translates the degree of twist into wind speed or the air speed of a flying individual.

According to paragraph 4, which of the following is true of insects and their antennae?

ASome insects do not develop antennae until the adult stage of life.

BInsects may have more than one pair of antennae.

CThe sensory function of antennae in insects varies according to species.

DThe function of antennae is partly determined by where they are located on an insect’s head.

 

8

In some other insects, notably saturniid moths, the antennae of the males are greatly enlarged and featherlike in order to accommodate an enormous number of odor receptors. The males use these to perceive an airborne sex-attractant pheromone, a chemical signal that is emitted by the females of their species. When a male smells this pheromone, he flies upwind, often for a considerable distance, until he finds the female. Male mosquitoes also use their antennae in locating females, but in their case the bushy antennae function as sound receptors that are set to vibrating by the sound waves, perceptible to us as a humming tone, that are produced by the beating wings of a female. Unmated male mosquitoes confined in a cage without females are excited by a tuning fork that vibrates at about the same pitch as do the wings of flying female mosquitoes.

Why does the author mention the effect of a tuning fork on caged mosquitoes in paragraph 5?

ATo compare the sound-processing capacities of insects and humans

BTo explain that man-made instruments can cause the release of chemical signals in insects

CTo describe the exact pitch of a mosquito’s wingbeat

DTo emphasize the responsiveness of male mosquitoes to sound waves produced by the beating wings of females

 

9

Look at the four squaresthat indicate where the following sentence could be added to the passage

That simple eyes play this role has been confirmed by experimental studies.

Where would the sentence best fit？Click on a square  sentence to the passage.

10

Insects have unique sensory organs which provide them with information about the world.

AThe compound eyes of insects are made up of numerous independent visual units that each contain their own lens and provide greater visual clarity as they increase in number.

BMany insects have simple eyes that exist along with compound eyes and sometimes have the function of regulating activity cycles by detecting changes in light.

CAntennae are important sensory organs that perform different tasks in different insects, including the assessment of air movement and temperature, as well as sensitivity to sound and touch.

DThe number of visual units in insects depends mainly on the insect species, for example, winged insects have many more visual units than unwinged insects since flying requires more precise vision.

EInsects see more colors than birds do since insects must be able to detect the wide range of colors in the nectar-producing flowers which provide them with food.

FThe antennae of male moths and mosquitoes are responsive to the sound signals of females during the period of mating but are less responsive during other kinds of activity.

 

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