Smells that Repel
Smells that Repel
Colors that announce “I taste bad” or “I am poisonous” are often enough of a warning to potential predators. Just in case these animals fail to believe their eyes, warning smells may be sent to their noses as well. Animals that are well camouflaged may rely entirely on smelling bad.
Scientists have also found that these strong odors are usually
accompanied by irritating chemicals. Just as a strong-smelling
onion irritates a person’s eyes, an animal’s strong-smelling fluids
can irritate a predator’s eyes, nasal passages, lungs, or skin.
Strong odors are frequently used as a defense by many insects known as “true bugs.” True bugs have beaklike mouthparts for piercing and sucking in food. Many of them also have stink glands. These stink glands are located on their backs when they are young and on their sides when they are adults.
The smelliest of all are the stink bugs. Stink bugs ooze a vile-smelling liquid if they are disturbed. The odor is described as smelling like a mixture of several pungent aromas—everything from licorice and overripe fruit to rotten eggs and skunk. It is strong enough to repel many birds, lizards, and other animals that eat insects.
Some stink bugs are brightly colored, such as the red and black two-spotted stink bug, but others are green or brown and blend in with their surroundings. Most walkingstick insects are also well camouflaged because they look like green or brown twigs. Not so the Peruvian walkingstick, which calls attention to itself with vivid red, black, and yellow markings. Its pattern warns “stay away,” and so does the strong-smelling white fluid it oozes when it senses a threat. The fluid irritates any ant or spider that persists in trying to eat the walkingstick.
The caterpillars of different swallowtail butterfly species have warning colors, camouflage, or eyespots for startling predators. Some species also are poisonous. All have a forked, tongue-like body part that pops out from behind the head. It gives off a strong smell when the caterpillar is under threat. The smell of these caterpillars is often compared to dirty socks.
Other small animals also give off strong odors when threatened. A daddy longlegs puts out a smelly liquid from glands on its back when its body is grabbed. The liquid spreads across its body and repels attackers, such as ants.
Millipedes also give off strong odors if they are disturbed. Just the scent of some millipedes is enough to send ants scurrying away. The strong odor comes from fluids that ooze from pores in the millipede’s sides.
A millipede may let out fluid only from the pores close to the site of the attack. If this is not enough, it will discharge fluid from the rest of its pores, too. The fluid from some millipedes is not only smelly and irritating, but also sticky. Ants that attack such millipedes become slimed with the gluey fluids and must work hard to free themselves.
Colors that announce “I taste bad” or “I am poisonous” are often enough of a warning to potential predators. Just in case these animals fail to believe their eyes, warning smells may be sent to their noses as well. Animals that are well camouflaged may rely entirely on smelling bad.
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| If disturbed, stink bugs—like this spined stink bug—emit a strong almond smell that is offensive to many animals. |
Strong odors are frequently used as a defense by many insects known as “true bugs.” True bugs have beaklike mouthparts for piercing and sucking in food. Many of them also have stink glands. These stink glands are located on their backs when they are young and on their sides when they are adults.
The smelliest of all are the stink bugs. Stink bugs ooze a vile-smelling liquid if they are disturbed. The odor is described as smelling like a mixture of several pungent aromas—everything from licorice and overripe fruit to rotten eggs and skunk. It is strong enough to repel many birds, lizards, and other animals that eat insects.
Some stink bugs are brightly colored, such as the red and black two-spotted stink bug, but others are green or brown and blend in with their surroundings. Most walkingstick insects are also well camouflaged because they look like green or brown twigs. Not so the Peruvian walkingstick, which calls attention to itself with vivid red, black, and yellow markings. Its pattern warns “stay away,” and so does the strong-smelling white fluid it oozes when it senses a threat. The fluid irritates any ant or spider that persists in trying to eat the walkingstick.
The caterpillars of different swallowtail butterfly species have warning colors, camouflage, or eyespots for startling predators. Some species also are poisonous. All have a forked, tongue-like body part that pops out from behind the head. It gives off a strong smell when the caterpillar is under threat. The smell of these caterpillars is often compared to dirty socks.
Other small animals also give off strong odors when threatened. A daddy longlegs puts out a smelly liquid from glands on its back when its body is grabbed. The liquid spreads across its body and repels attackers, such as ants.
Millipedes also give off strong odors if they are disturbed. Just the scent of some millipedes is enough to send ants scurrying away. The strong odor comes from fluids that ooze from pores in the millipede’s sides.
A millipede may let out fluid only from the pores close to the site of the attack. If this is not enough, it will discharge fluid from the rest of its pores, too. The fluid from some millipedes is not only smelly and irritating, but also sticky. Ants that attack such millipedes become slimed with the gluey fluids and must work hard to free themselves.
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