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Communication
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Communication in insects and people differ in many ways.
Insects and people both use touch, visual signals, and sound
to pass information to others. However, insects also have
many different kinds of chemical signals. One communication
signal from an insect usually results in only
one kind of response. In people, one signal can result in
many different responses.
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If insect communications were put into words, this is what we
might hear. "Hey, I found some food!" "Let's get out of
here!" "Do I know you?" "Come over to my house." Insect
communication can result in such responses as alarm, attraction,
grooming, exchange of food, and recognition. It can affect a
single individual or a group of individuals. Some
communication signals are transmitted and understood only
within a species, whereas other signals cause a response in
another species.
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Touch Communication
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Most touching involves the antennae and mouth parts, but not
much information is passed by this form of communication.
Touching can be used for recognizing nest mates, especially
those that live in darkness. For example, a mole cricket
mother recognizes her nymphs in a dark burrow by touching them
with her antennae and even picking them up with her mouth
parts.
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Social insects, such as ants, often stroke and groom each
other with their antennae and mouth parts. However, both
touch signals and chemical signals may be involved in these
behaviors.
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The waggle dance of the honey bee involves an advanced form of
touch communication. A scout bee that locates a new field of
flowers will return to the hive and perform a waggle dance on
the vertical comb. This dance is somewhat in the shape of a
figure eight (8). The bee makes two half circles in opposite
directions with a straight run between the two half circles.
The bee waggles, or shakes, her abdomen when making a straight
line across the middle part of the "8." The other bees crowd
around and touch the dancing bee with their antennae. The
dance tells the other bees which direction and how
far to fly to find the flowers. Sometimes the dancing bee
makes the figure "8" sideways, like "oo". If the dancing bee
goes straight up through the middle of this "oo" (180 degrees
opposite the pull of gravity), the other bees know the field
of flowers is directly toward the sun. A straight downward
run by the dancing bee indicates that the field is directly
opposite the sun. All other directions are shown by the
different angles of the straight run relative to the vertical
up and down. For example, if the bee runs upward at an
angle of 30 degrees to the left of vertical, the field of
flowers will be 30 degrees to the left of the sun. The number
of waggles in the straight line of the dance, along with
pulsing sounds from the dancing bee, tells the other bees how
far to fly.
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Visual Communication
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Several kinds of flies and beetles can make light. Fireflies
(also known as "lightning bugs") are actually beetles that can
make flashes of light. The two sexes of these beetles use
different codes of flashes to find and recognize each other.
The adult firefly produces light in an organ at the end of
its abdomen. This light is made when the beetle opens
certain air tubes (trachea) so that oxygen can
mix with a substance known as luciferin.
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Each species of firefly has a different kind of flash pattern.
Photinus pyralis, for example, makes a single long flash that
is J-shaped as the beetle dives downward while flying.
Another species may fly in a straight line and give off three
slow flashes in a row, like this: "...flaaash....flaaash....
flaaash...". A third species may make single flashes that get
brighter at their end, like this:"...flasH...flasH...flasH...
flasH..."
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Many butterflies, flies, and other insects use colors for
visual communication. Males of some flies have bright spots
on their wings. They communicate with females during courtship
dances by flitting their colorful wings. Some butterflies
have patterns of ultraviolet color on their wings, which people
can't see without special instruments. These ultraviolet color
patterns are essential for visual communication during courtship
of the two sexes of the butterfly.
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Some insects have bright red or orange colors that are exposed
only when they are threatened by a predator. For example, if
a lubber grasshopper is disturbed, it will flash its bright
red hindwings. The sudden display of bright red may scare the
predator and give the grasshopper time to escape. This is an
example of a visual communication that is passed to another
species.
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Sound Communication
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Insects in many orders make sounds to attract individuals of
their same species or to cause a response in another species.
Sounds are caused by vibrations that can pass through air,
water, and solid structures. Although people can hear crickets
and cicadas, many insects make supersonic sounds that are
above a person's range of hearing. These supersonic sounds
have more than 20,000 vibrations each second.
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Sound can be made during normal activities of insects, such as
eating or flying. Male and females of some mosquitoes are
attracted to each other by the sound of their buzzing wings
when flying. Different species of mosquitoes and other flies
have different sounds in flight because of differences in the
speed of their wing beating.
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Many years ago, it was the custom to never leave a dead person
alone until after their burial. Someone would stay up with
the dead person through the night in the "death-watch." Late
at night when the house was quiet, a tapping sound could be
heard coming from the walls. This sound was made by beetles,
now known as death-watch beetles, that eat the wood in old
houses. The death-watch beetles strike their heads
against the roof of their tunnel to make the tapping sound,
and this sound attracts the opposite sex of the beetle.
Making sound by striking some part of the body against a hard
surface occurs in many other insects, including termites and
stoneflies, and even in some spiders.
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The rubbing of body parts together to make sound is known as
stridulation. The chirping sounds of crickets and katydids
are made by rubbing a file of pegs on one forewing against a
scraper on the other forewing. Grasshoppers rub their legs
against their wings to advertise their presence. Many true
bugs, beetles and ants make sounds by rubbing various other
body parts together. Often the sounds of these insects
cannot be heard by a person unless the sounds are recorded
through a microphone and amplified.
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Drum-like membranes can vibrate to make sound in many insects,
especially Homoptera. The cicadas are among the loudest of all
insect singers and can be heard by a person for more than a
half mile. In the cicada, the vibrating membrane is
surrounded by hollow areas that amplify the sound. The songs
of cicadas differ for every species, as you can hear in the
Phantastic Songs of the S. E. Asian Cicadas.
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The Madagascar hissing cockroach makes sound in an unusual way.
Whenever it is disturbed, the cockroach hisses by blowing air
out of its spiracles. Some moths can make sound by blowing
air through their proboscis.
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Chemical Communication
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Many insects communicate with chemicals that are secreted by
the insect's glands into the environment. Two of the
different types of chemical messages are pheromones and
allomones. Pheromones are chemical messages for members of
the same species. Allomones are messages that are directed
towards different species for defensive purposes.
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Sex pheromones are attractants for members of the opposite sex
of a species. The "perfumes" of some females can be detected
by males that are more than four miles away. Sometimes a
sex pheromone includes a mixture of many different chemicals
that only one species will recognize. If two different species
use the same chemical to communicate, they may send their
chemical messages at different times of the day. Because of
different chemicals or different times of communicating, the
male of one species is not attracted to a female of another
species.
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Some pheromones are released to attract many individuals
together, including both sexes. These are called aggregation
pheromones. If one bark beetle (Family Scolytidae) female
finds a tree suitable for infesting, it will release an
aggregation pheromone to attract large numbers of beetles to
the same tree.
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Alarm pheromones are released by insects that are disturbed or
threatened. If an ant's nest is disturbed, the alarm pheromone
causes many ants to run about the mound to attack the invader.
Other ants will gather eggs and larvae to escape.
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Trail pheromones are used by many ants, caterpillars, and
other insects. These chemicals are used as a road map for
finding food. After the ant finds some food, it will find
its way home by this chemical trail, and other ants can follow
it to the food.
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Defensive chemicals, or allomones, are used to protect one
species from the attacks of another species. The odor of
some defensive chemicals, such as those of stink bugs (Family
Pentatomidae), is very unpleasant to people. Some of these
chemicals can be very painful and even cause temporary
blindness if they are squirted into the eyes of birds or people.
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Picture Credits
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Dr. Ross E. Hutchins (Deceased)
Mississippi Entomological Museum
Campanotus communicating with antennae
Honey bee's waggle dance for directions
Firefly beetle flashing light
File and scraper on katydid wings
Sound organs of cicada
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