Insects have become very specialized in the ways they avoid being eaten by other animals. Read this article
and answer the questions that follow.
Surviving, for Better
and Worse
by Marc Zabludoff
1 Nearly all insects are hunted as food, and not just by other insects. Birds, mammals,
lizards, snakes, frogs, toads, and especially spiders all depend on insect meals for
their survival.
2 Insects, naturally, have developed a few ways to avoid joining any of these
companions for dinner. Their principal response to attack is to try to escape. No
matter how well-armed or -legged an insect might be, it is always far better to flee
than to fight. The need to escape predators was surely at least one of the pressures
behind the development of insect wings. Wings enable insects to accomplish several
other important tasks, of course, such as finding food, mates, and new territory. But
their value as an escape tool is very high.
3 Certain insect bodies have developed other specialized parts for escaping a hungry
predator’s claws and jaws. These include jumping legs in froghoppers, for example,
or “ears” in certain night-flying moths that can hear the echolocating calls of bats.
(Echolocation is the sound-wave process some animals use to identify and locate
objects.) More generalized features include the flattened body of roaches and bugs
that allow them to squeeze into impossibly narrow hiding places.
C H E M I C A L W E A P O N RY
4 A large variety of insects try to avoid predators by making themselves extremely
unpleasant to eat. Most children have learned that grasshoppers, for instance, spit
“tobacco juice” when threatened. The juice is actually the partly digested food from
the insect’s crop, and it is not so much spit as vomited. It is as unappealing to some
predators as it sounds (though not to all—some predators have no taste). Other insects
have similar defenses. Stinkbugs, for example, simply stink. Certain water beetles fire
pellets of waste from their rear ends as they swim away from pursuing fish.
5 These are all mild forms of chemical
warfare. Bombardier beetles go in for a
more serious version. These insects get
their name from their ability to “bomb”
an attacker with a series of gas explosions
from their abdomen. A mixture of
chemicals inside their body results in the
emission of a hot, brownish spray that can
burn any predator that gets too near. Other
beetles ooze out peppery liquids, some
from their legs, others from glands inside
their forewings. These substances are often
powerful enough to burn human skin.
6 Many insects make sure they are not
just bad tasting but poisonous. Monarch
butterflies, when caterpillars, gorge1
themselves on the leaves of milkweed plants. A chemical in the leaves guarantees
that a predator foolish enough to eat a monarch caterpillar will soon vomit up its
meal. If it does not, it will die. Adult butterflies continue to carry the milkweed
poison they ate as youngsters.
7 Of course, this method of defense does little for the butterfly that has already
been eaten. By the time the predator learns its lesson, the butterfly is history. But
it does protect other butterflies in the future. And poisonous insects usually try to
get their message across before being eaten. Most of them are brightly colored or
marked with bold black-bordered stripes.
M I M I C RY A N D C A M O U F L A G E
8 The monarch’s poison defense is so effective that another butterfly, the viceroy, uses
it also. Unlike the monarch, though, the viceroy cannot eat milkweed. In fact, any
predator can munch on a viceroy with no ill effects whatsoever—no vomiting, no
dying. However, the viceroy has evolved so that it sports the same orange wings
with black lines and white spots that adorn the monarch. Birds that have learned to
avoid the poisonous monarch will avoid the non-poisonous viceroy as well.
9 This kind of defense is called mimicry, and it is not limited to butterflies. Stinging
insects, for example, like bees, are often marked by black and yellow stripes that
predators quickly grow wary of. The drone fly has taken advantage of this by evolving
a striped body similar to that of a bee. Many predators, seeing the drone fly’s black
and yellow outfit, simply let it pass. In fact the drone fly is harmless, its weaponry
non-existent.
1 gorge — to eat large amounts
When threatened, a bombardier beetle mixes
an array of chemicals in a chamber in its
abdomen. Combined, the chemicals explode
out in a hot spray that sends predators
running.
10 Other insects try not so much to look like something else as to look like nothing
at all. They camouflage themselves so that they fade into the background. Stick
insects blend in among twigs and bark. Treehoppers look, and often feel, like thorns.
Leaf butterflies look convincingly like dead leaves. Some caterpillars look like bird
droppings.
11 No matter what defense an insect relies on, the brutal truth is that very few of
them will die of old age. Insects are a vast food source for animals of every kind,
including the insects themselves. In addition, despite the exquisite2 design of the
insect body, it is still a small fragile thing when compared with the physical forces of
weather. Insects can avoid some of the effects of nature. Most can go into a resting,
or hibernating, state as an egg or larva or even as an adult. Ladybugs in California,
for example, gather in huge colonies to hibernate in the mountains in winter, then
return to the valleys in the spring. While they are resting, each ladybug releases a
small amount of a predator-repelling substance. The total volume of it protects them
all. Other insects migrate to avoid the cold. Monarch butterflies escape winter by
flying south—sometimes as much as 2,000 miles (3,200 km) from Canada to Mexico.
12 Still, the weather takes its toll, and what the elements do not kill, the predators
will. Only a relatively few insect eggs ever hatch. Few of those that do ever make
it to adulthood. The odds against an insect egg developing into an insect parent are
very, very high. Of course, insects lay a staggering number of eggs. And the world
is still populated by a staggering number of insects.
“Surviving, for Better and Worse” by Marc Zabludoff, from The Insect Class. Copyright © 2006 by Marc Zabludoff. Reprinted by permission
of Marshall Cavendish. Photograph copyright © Handout/Reuters/Corbis.
2 exquisite — finely detailed Write a critical idea for passage 2: Basic Writing requirements: 1. Organize your ideas logically, maintain a formal style of writing, and follow the conventions of standard written English. Writing format requirements: 1. Times New Roman 2. 12 point font 3. Black text 4. Indentations: for the first line of a new paragraph, you should indent (use “tab” key) in 2-3 sentence written like a 8th grader in 35 word length
Insects have developed various specialized ways to avoid being eaten by other animals. Their main response to attack is to try to escape, as it is always better to flee than to fight. Insect wings have evolved as an escape tool, allowing them to find food, mates, and new territory. Certain insects have also developed specialized parts for escaping predators, such as jumping legs in froghoppers and "ears" in night-flying moths that can hear the echolocating calls of bats. Some insects have flattened bodies, enabling them to squeeze into narrow hiding places.
Insects also use chemical warfare as a defense mechanism. Grasshoppers, for example, spit "tobacco juice" when threatened, which is actually vomited partly digested food. Stinkbugs simply stink, and certain water beetles fire pellets of waste from their rear ends while swimming away from pursuing fish. Bombardier beetles take chemical defense to a more serious level by "bombing" attackers with a series of gas explosions from their abdomen, resulting in a hot, brownish spray that can burn predators. Other beetles ooze out peppery liquids that can cause burns on human skin.
Many insects are not just unpleasant to eat, but also poisonous. Monarch butterflies, when caterpillars, eat milkweed leaves that contain a chemical guaranteeing that any predator foolish enough to eat them will vomit up the meal or die. Adult butterflies continue to carry the milkweed poison they consumed. Poisonous insects often have bright colors or boldly marked patterns to communicate their toxicity to predators.
Mimicry is another defense strategy used by insects. The viceroy butterfly, for instance, looks very similar to the monarch butterfly but is not poisonous. Birds that have learned to avoid the poisonous monarch will also avoid the viceroy. Stinging insects like bees are often marked with black and yellow stripes that predators have learned to avoid. The drone fly has evolved a similar striped body to mimic a bee, taking advantage of the predators' aversion to the black and yellow pattern.
Some insects rely on camouflage to blend into their surroundings. Stick insects blend in with twigs and bark, treehoppers resemble thorns, and leaf butterflies resemble dead leaves. Some caterpillars even look like bird droppings.
Ultimately, despite their various defense mechanisms, very few insects die of old age. They are a significant food source for many animals, including other insects. In addition, the physical forces of weather can also impact their survival. However, insects have developed strategies to mitigate these effects, such as hibernation, rest states, or migration. The odds of an insect egg developing into an adult insect are low, but insects reproduce in large numbers to compensate for this.