Beetle: Difference between revisions

Beetles
Colorado potato beetle, Leptinotarsa decemlineata
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Neoptera
Superorder:	Endopterygota
Order:	Coleoptera Linnaeus, 1758
Suborders
Adephaga Archostemata Myxophaga Polyphaga

Beetles are a kind of insect. Biologists call all beetles as a group Coleoptera. There are 350,000 different kinds (species) of beetles. Beetles live almost everywhere, but not in the ocean or in places that are very cold, such as the North Pole or South Pole.

People sometimes call some beetles by other names. Fireflies (also called lightning bugs) are actually beetles; so are ladybirds or ladybugs, which scientists call lady beetles.

Beetle bodies

Beetle bodies have the same three main parts as all insects have: the head, the thorax (the middle part), and the abdomen (the back part). On the head, beetles have antennae (feelers), eyes, and a mouth. The legs and wings of the beetle come out of the thorax. The abdomen of a beetle does not usually have special parts on the outside of it, but it has the beetle’s stomach and intestines inside. Like other insects, beetles are hard on the outside because of an exoskeleton, which is similar to bones on the outside of the body. Beetles have no bones inside them. The exoskeleton is made of hard plates, like pieces of armour.

Wings

The back wings of a beetle are see-through. This beetle will use its back wings to fly. The hard front wings are lifted up.

The hard front wings of the beetle hide the back wings.

Beetles are different from other insects because of their wings. Beetles have four wings. The front pair (two wings) is hard and does not help the beetle to fly. The front wings cover the back of the beetle. The front wings also hide the back wings when the beetle is not flying. The back wings are used for flying. They are thin and need the front wings to protect them. Beetles must first lift the front wings out of the way in order to fly. Most other insects do not have hard front wings and soft back wings. Only some true bugs also have hard front wings.

Not all beetles can fly. Some beetles do not have back wings, and some beetles cannot lift their front wings out of the way. Only a few beetles have no wings at all and can never fly. Beetles with no wings look similar to beetle larvae, so they are called larviform.

Legs

The legs of beetles help them to walk, run, swim, and dig. All beetles have six legs. Each leg is made out of several parts. The parts on the end of each leg are often the smallest. They are similar to feet but are called tarsi. The last tarsus (the singular of tarsi) of each beetle “foot” has one or two claws on the end of it. Most beetles use their legs to walk or run. Some beetle legs are flat and have long hairs on them. These kinds of legs are found on water beetles and are good for swimming. Some beetle legs are flat and have spines or horns on the edge of them. Beetles that often dig in soil have legs like that. Flat legs with horns are called fossorial legs because they help with digging. As few beetles have big hind legs, similar to those of grasshoppers. These big hind legs help the beetle to jump. Some of these jumping beetles are called flea beetles.

Sight and smell

Beetles have compound eyes, which means the two big shiny eyes on the head are actually made out of many smaller parts. Sometimes the two eyes are each divided in half so that it looks like there are four eyes. One beetle family, the whirligig beetles, has divided eyes so that when they are swimming they can see on top of the water and inside the water at the same time. A few beetles have extra simple eyes (usually two) called ocelli. The ocelli are on the top of the beetle’s head.

Because beetles have no nose, they use their antennae to smell things. Beetles also use their antennae to feel things around them. Sometimes, beetles use their antennae for strange things. Some beetles use their antennae to fight other beetles or even to fight larger animals that want to eat them. Beetle antennae do not all look the same. Some antennae are long and thin, while others are short and wide. Thin antennae are called filiform antennae, and antennae that are wide on the end are called clavate antennae.

The mouth

The mouth of a beetle is very different from the mouth of a person. Most beetles have two hard things like teeth in front of their mouth, called mandibles. In some beetles, the mandibles look like big pinchers on the front of the beetle. Mandibles help the beetle eat because they crush and cut food. Beetles also have four “fingers” around their mouth that push food into the mouth of the beetle. These fingers are called palpi.

Other

Beetles do not breathe air into their mouths; they have holes called spiracles in the sides of their bodies. These spiracles lead to trachea, which act like lungs, but beetles do not have lungs. Beetles do not have blood, but they have something like blood, called hemolymph. It flows in their bodies and is usually a green colour.

How beetles grow

An example of a scarabaeiform larva

Beetles start out as eggs that a female beetle lays. Some beetles can lay thousands of eggs during their lives. A larva comes out when an egg hatches. Most beetle larvae do not look like adult beetles. A beetle larva eats and grows larger until it changes and becomes a pupa. When the pupa opens, an adult beetle, sometimes called an imago, comes out. This way of growing up is called complete metamorphosis.

Beetles eat the most when they are larvae. Some beetle larvae eat the outside of plants; some eat inside plants. Some beetle larvae are predators, which means they hunt for other insects to eat. Other beetle larvae eat dead things, such as dead plants and dead animals.

Not all beetle larvae look the same. Some beetle larvae are flat and move very fast. To describe these larvae, scientists use the descriptive word campodeiform. Some beetle larvae look similar to hard worms with tiny legs. These have an elateriform shape. The larvae of click beetles are elateriform larvae. Click beetle larvae have a special name: wireworms. Other beetle larvae are short and very thick and are called grubs. Scientists say that grubs have a scarabaeiform shape. In a few beetles, the larvae change its shape after some time. Blister beetle larvae start out moving fast, such as campodeiform larvae, but end up slow and thick, more similar to scarabaeiform larvae.

What beetles do

Food

Beetles eat many different things. Some beetles eat living plants. Some beetles eat dead things, such as dead leaves, dead animals, and even animal feces. Some beetles can eat both plants and animals.

There are also beetles that are very specific in what they eat. These beetles can only eat one kind of plant or one kind of other insect. Beetles that can only eat one kind of thing are said to be host specific. Many leaf beetles and longhorn beetles are host specific.

Protection

There are many animals that want to eat beetles and beetle larvae. Animals that eat other animals (and that eat beetles) are called predators. Sometimes beetles eat each other. Other insects and spiders sometimes eat beetles. Larger animals, such as birds and mice, also eat beetles. How do beetles protect themselves?

Some beetles live in places that are hard for predators to find. Some beetles, such as longhorn beetles, live in tunnels inside tree branches. Only special predators that are small enough to use the long-horned beetle tunnels can eat the longhorn beetles.

Other beetles do not live in special places but they have colours or shapes that make them hard to find. When beetles have colours so that predators cannot see them, this is called camouflage. Some leaf beetles are green so that they can not be seen when they are on green leaves. Some beetles have very complex colours so that they look like bird feces.

Sometimes beetles use colour to scare predators. Some beetles have black and yellow stripes so that they look similar to bees and wasps. Some beetles even behave similar to bees to confuse predators.

Many beetles taste bad when predators eat them. Lady beetles taste bad. Lady beetles also have colours that warn predators that they taste bad: bright colours with dark spots often means a beetle has a bad taste. Some beetles with bright colours and dark spots or lines are actually poisonous. Blister beetles are so poisonous that if a horse eats only a few of them, the horse will die!

Very large beetles sometimes fight predators. Beetles that fight will often use their mandibles as teeth to bite their predators.

Reproduction

Beetles have sexual reproduction, which means males and females mate in order to make offspring.

Before reproduction, male beetles sometimes fight to claim a female. This especially happens with stag beetles: males will fight using their long mandibles.

Some beetles give special care to their eggs or larvae. Some scarab beetles, called dung beetles, roll balls of dung (feces) and put them in a hole in the ground. The female lays her eggs in the dung. When the eggs hatch, the larvae will eat the dung that their mother supplied for them.

Kinds of beetles

Different kinds of beetles can be divided into groups called families. There are many beetle families. The biggest families are listed here.

• Ground beetles (family Carabidae) are often black and can be found under rocks.
• Leaf beetles (family Chrysomelidae) usually eat on the outside of plants.
• Longhorn beetles (family Cerambycidae) have very long antennae. Most longhorn beetle larvae eat on the inside of plants.
• Weevils (family Curculionidae) have long faces that look like the trunk of an elephant.
• Scarab beetles (family Scarabaeidae) have antennae that are wide on the end. Some scarabs are called dung beetles. Other scarabs are very colourful.
• Rove beetles (family Staphylinidae) have short front wings that do not cover their bodies.

Beetles and people

Some beetles cause trouble for farmers and people in forests because they eat crops or trees. These beetles are called pests. One beetle that hurts crops is the Colorado potato beetle.

Other beetles help people; lady beetles (also called ladybirds and ladybugs) eat insects that hurt crops and trees.

People who study beetles are called coleopterists.

General references

• Arthur V. Evans, Charles Bellamy, and Lisa Charles Watson, An Inordinate Fondness for Beetles ISBN 0-520-22323-3
• Entomological Society of America, Beetle Larvae of the World ISBN 0-643-05506-1
• Ross H. Arnett, Jr. and Michael C. Thomas, American Beetles (CRC Press, 2001-2). ISBN 0-8493-1925-0
• K. W. Harde, A Field Guide in Colour to Beetles ISBN 0-7064-1937-5 Pages 7-24
• White, R.E. 1983. Beetles. Houghton Mifflin Company, New York, NY. ISBN 0-395-91089-7

See also

• True bug - These are insects that look similar to beetles.