Beetle Identification and Guide to 21 Common Types

If you have a garden or own a home, then this quick and easy guide will help you identify a group of insects that you almost certainly come across on a daily basis: the beetles. Most beetles are harmless, and many are actually quite helpful to both gardeners and homeowners. There are a few, however, that can cause damage to plants or structures, or are otherwise undesirable. I have always been struck by how beautiful these often-overlooked animals can be, especially close-up. Their habits and life histories are also frequently amazing.

Overall, beetles are a group of insects that are worth getting to know. Being able to identify the beetles around your garden and your home is a good first step.

Stag beetles

Hercules beetle

Grapevine beetle

Ten-lined June beetle

Japanese beetle

Ground beetles

Tiger beetles

Carrion beetles

Weevils

Sawyer beetles

Emerald ash borer

Whirligig beetle

Carpet beetles

Striped cucumber beetle

Eyed click beetle

Soldier beetles

Blister beetles

Fireflies

Fiery searcher

Bombadier beetle

Ladybird Beetles

Stag beetles are often very spectacular insects with huge mandibles, or "pincers," which give the insect its common name -- the mandibles on some look like the horns of a stag deer. Stag beetles are shiny brown or black, usually quite large, and have pronounced mandibles that are smaller in the females. As a matter of fact, their smaller, stouter pincers means the female can deliver a much more painful bite than the male.

Stag beetles are not venomous or harmful in any way. The larvae live in rotten stumps and logs and prey on the insects there. The adults often fly to lights on warm summer nights.

The Basics:

Scientific Name: The most common North American species are in the genus Lucanus

Size: Up to two inches in length

Habitat: Larvae live in rotten wood; adults often fly to lights at night

Range: Throughout the USA and southern Canada

Notes: These beetles are harmless, although the females can deliver a pinch with their short, sharp mandibles.

These very large beetles are in the genus Dynastes, which is found throughout the Americas. Tropical species are among the largest insects in the world. In the United States, Dynastes beetles are generally uncommon, although the beautiful, black-spotted eastern Hercules beetles, Dynastes tityus, is occasionally found in large colonies on trees. These insects are harmless despite their large size and the male's huge horns.

The Basics:

Scientific Name: These beetles are in the genus Dynastes.

Size: Up to two inches in length

Habitat: Larvae live in rotten wood; adults sometimes congregate on old trees.

Range: Throughout the eastern USA

Notes: Despite their fearsome horns, these beetles are harmless.

This large, handsome beetle is often found at lights in early summer, hence one of its other common names, the spotted June beetle. The adults are harmless and feed on grapevines, generally causing very little damage, and are not considered a pest. There are two variations of this species, one in the North and one in the South (the northern version has darker legs).

This insect lives in Eastern North America, as far south as Florida; its range extends west to Nebraska and eastern Kansas. They are very active fliers and will quickly take to the air if disturbed, although they can be safely handled. They live in woods, hedges, and overgrown areas, where the larvae (grubs) feed on rotten wood under the soil; they pupate in shallow chambers and the adult beetle emerges in the summer.

The Basics:

Scientific Name: Genus Pelidnota

Size: Up to one inch in length

Habitat: Larvae are grubs that live under soil and feed on roots; adults eat the leaves of grape and other plants

Range: Throughout the eastern USA

Notes: These beetles are related to the more common brown "June bug."

Like the grapevine beetle (above) to which it is related, this is a large, showy beetle that often shows up at lights around homes and urban areas. However this beetle is confined to the American Southwest, where it can be very common.

Ten-lined June beetles have an interesting way of defending themselves, which you may know about if you have ever tried to pick one up. If you grab them or bother them, these beetles will suddenly make a loud, vibrating buzz that zings your fingers and is quite startling.

The Basics:

Scientific Name: Polyphylla decemlineata

Size: Large; about one inch in length

Habitat: Larvae are grubs that live under soil and feed on roots

Range: Throughout the Southeastern USA

Notes: These big, beautiful insects are completely harmless to humans

The Japanese beetle is one of the most destructive pests in the United States, chewing its way through the leaves of upwards of 300 different species, especially rose, grapes, linden, and crepe myrtle. It's also one of the prettiest beetles in North America, with copper-colored wing covers (elytra) and an iridescent green thorax and head. This beetle flies very well, and resembles a bee as it hovers among the flowers and blossoms of your backyard primrose.

P. japonica is native to Japan, where its population is controlled by natural predators. In North America, however, P. japonica is an invasive species, with few to none of the natural predators that keep its numbers in check in Japan. The first written evidence of this beetle's invasion of North America is from 1916, when it showed up in a New Jersey greenhouse, hungry and ready to stage a take-over. At present, only nine states, all in the West, are free from this pest.

The Basics:

Scientific Name: Popillia japonica

Size: About a half-inch in length

Habitat: Larvae are grubs that live under soil and feed on roots; adults eat the leaves of more than 300 plants

Range: Throughout the eastern USA

Notes: This invasive species has only been in the US for about 100 years

Ground beetles in the subfamily Carabinae make up a very large group of beetles, many of which are those similar-looking brown or black beetles you see scurrying across the sidewalk. These ground beetles live under stones and logs, or under your porch, and they are totally harmless to humans: in fact, they do humans a service by preying on some less-desirable insects like ants.

It's unusual to see these beetles inside your home, so if you have a bug, or bugs, that look like beetles around your house, you should have a closer look -- they could be roaches. Cockroaches are an entirely different group of insects from beetles, and if you do have cockroaches, you should take steps to get rid of them.

The Basics:

Scientific Name: Subfamily Carabinae

Size: Most are less than an inch -- a few are quite large

Habitat: These beetles live outside, under stones and logs, and prowl around looking for small insects to eat

Range: These beetles have a world-wide distribution

Notes: Although they may look like cockroaches, you will rarely find ground beetles inside your home.

Tiger beetles are very cool insects that most people hardly notice, even though they are quite common. These beetles often occur in sandy areas, but some show up on hot summer sidewalks. They have long legs, big eyes, and sharp pincers, and they are jumpy and nervous -- tiger beetles will fly if you get too close and land about 5 feet away, repeating the action if you move towards them.

I always loved trying to catch tiger beetles in the summer when I was a kid. Many are very beautifully colored in iridescent green and blue, and the challenge of grabbing one can keep a kid occupied for hours.

The Basics:

Scientific Name: Family Carabidae; Subfamily Cicindelinae

Size: About a half-inch in length

Habitat: Hot, flat surfaces where they prey on other insects

Range: Throughout the USA, including deserts

Notes: There are many similar-looking species in this group, which makes identifying them a challenge for amateurs and professional alike

If you come across a dead bird or mouse, there's a good chance that some of these beetles will be on the scene. They are large and brightly colored, which makes them hard to miss. Carrion beetles are also sometimes called "burying beetles," because some species dig a hole under the carcass until it falls in. Then the beetles lays eggs on the food source and covers it up. This group has many other fascinating habits, all of them on the gross side, but true scientists, citizen or otherwise, aren't fazed by a little carrion.

There are two common species in this group that look very different. Most Silphidae beetle are good flyers and sometimes come to lights.

The Basics:

Scientific Name: Family Silphidae; various species around the world

Size: Medium-sized beetles, up to about an inch in length

Habitat: Found wherever there are dead animals

Range: Throughout the USA

Notes: The habits of this insect are amazing in their adaptations to feeding on and around carrion

Weevils are generally small, harmless beetles with a pronounced nose or "snout." They are the most common kind of beetle in the world, and since there are more beetles than any other kind of animal on earth, that makes weevils the most successful animal out there. And you probably never even noticed them!

The place where most people encounter weevils is in the pantry, where a few species can become pests by invading stored beans and grains. Many people have also heard of the "boll weevil," which feeds on cotton and can ruin a cotton crop by damaging the fibers in the "boll."

Once you are tuned in to the world of small animals, you will certainly start noticing a weevil or two in your surroundings. Unless they're in your stored food, there's no reason to fear or harm these little creatures.

The Basics:

Scientific Name: Superfamily Curculionoidea; many species around the world

Size: Small-to-medium-sized beetles, up to about an inch in length

Habitat: Found just about everywhere; they have adapted to nearly every corner of the world

Range: Worldwide; possibly also on the moons of Jupiter

Notes: The habits of this insect are amazing in their adaptations to the food and conditions of virtually any environment

You will most likely encounter sawyer beetles on camping and fishing trips, in places where there are plenty of trees. The larvae of this beetles, which look a little like pale, tough caterpillars, bore into dead and dying trees; they especially like pine trees. The tunnels made by the larvae can ruin commercial timber, and the timber industry has found ways to preserve cut logs to keep damage from sawyer beetles to a minimum.

These big beetles are harmless to humans. They fly very well, and sometimes come to lights. The males are typically a hit smaller than the females, and usually have impressively long antennae, sometimes twice the length of the body.

The Basics:

Scientific Name: Genus Monochamus; they belong to a very large group called "longhorn beetles," family Cerambycidae

Size: Medium to quite large; some females measure over an inch

Habitat: Found wherever there are plenty of trees

Range: Throughout the USA

Notes: In addition to damaging timber by boring holes in wood, these beetles have been known to transmit disease between trees.

This small beetles has caused more havoc in American forests and parkways than any invasive species since the gypsy moth. Even though it is truly beautiful -- it belongs to a group of beetles also known as "jewel beetles" -- the emerald ash borer has shown how destructive and invasive species can be in a new environment with no predators in place to control it. If you live anywhere in the eastern part of the country, you are likely familiar with the death and removal of the beautiful ash trees that are a mainstay of urban greenery. For this you can thank the humans responsible for the careless importation of this little beetle.

As is so often the case with destructive species like carpet beetles and and clothes moths, it's the little, unseen larvae that do all the damage. They begin as eggs laid on bark, and then hatch and burrow into the tree. Over time, enough of them can do enough damage to a tree's vascular system to cause it to wilt and die.

In Asia, where it is endemic, the emerald ash borer occurs at low densities and is controlled by predators adapted to feed on the larvae and adults. In the US and Europe, it can undergo population explosions. If you find an insect that looks anything like the emerald ash borer, immediately call a local university, museum, or forestry office -- it's a legitimate emergency!

The Basics:

Scientific Name: Agrilus planipennis

Size: quite small, often less than half an inch

Habitat: Areas with the host, ash trees (genus Fraxinus)

Range: Originally Asia; now throughout the Western Hemisphere

Notes: This little beetle is one of the worst invasive species of our time.

There are many beetles that spend most or all of their time in the water, including some large predatory beetles that feed on small fish, among other things. Most people seldom encounter these insects, but one kind of "water beetle" is familiar to almost everyone who has spent time outdoors: whirligigs. These small, dark-colored beetles spend most of their time floating in large colonies on the surface of pond and other still water. When you, or any other being, disturbs them, they respond by frantically zig-zagging through the water, zooming in tight circles and creating real chaos. Of course this helps confuse predators. They are also very hard to hold; if you are quick enough to grab one of these insects (unlikely), it will quickly slip through your fingers thanks to its flat, slick surface and powerful, oar-like legs.

These beetles are harmless and not a little hilarious. They are a sweet part of summer, and if you have never seen a herd of whirligig beetles swimming manically around in circles, get to a quiet pond and have a look along the banks. They're there.

The Basics:

Scientific Name: Family Gyrinidae; several species that are all very similar

Size: Small to medium

Habitat: Found wherever there is still water

Range: Throughout the USA

Notes: Although they spend most of their time on the surface, whirligig beetles will dive if they feel especially threatened.

If you have ever worked in a museum, then you most certainly know about these beetles. The bristly larvae feed on dead, dried-out animal material, and an infestation can destroy irreplaceable collections of everything from insect to bird specimens. In the home, they can chew holes in carpets and wool, much the same as clothes moths do. Note that it's the larvae, not the adults, that cause the damage -- this is true of both beetles and moths.

There is one way in which Dermestid beetles are actually useful in museums, however. Since they have a voracious appetite for dead material, scientists often place animal corpses in a tank with hundreds of Dermestids in order to get a perfectly cleaned skeleton for study and display. It's not a pleasant thought, but all of those beetle larvae gobble up the skin, hair, etc, and leave the bone as clean as a whistle.

The Basics:

Scientific Name: Family Dermestidae; most are found in the wild, but a few species are well known pests

Size: Very small; usually about 1/4 inch in length

Habitat: Found wherever there are stored organic materials

Range: Throughout the world

Notes: These beetles can cause trouble in the home, but they can be devastating in museums, where large collections are sometimes consumed by this pest.

This small beetle can be a minor pest on your cucumbers and other cucurbits. These insects attack the plant from top to bottom: the adult beetles emerge en masse in the spring and begin feeding on leaves and flowers; the grubs live underground and eat the plant's roots. If there are enough of them, striped cucumber beetles can kill an otherwise healthy plant. Additionally, these beetles can transmit wilt diseases and other pathogens.

These insects look a lot like the western corn rootworm beetle, but their habits are very different.

The Basics:

Scientific Name: Acalymma Vittatum

Size: Small beetles, about a half-inch in length

Habitat: Your garden, and anywhere else there are cucumber plants

Range: Throughout the world

Notes: Two closely related species, the spotted cucumber beetle, Diabrotica undecimpunctata, and the banded cucumber beetle, Diabrotica balteata, are more common in Florida.

These amazing-looking beetles occur throughout the American South, where there are several different species. The big eye spots on the back of the insect's thorax are, of course, not really eyes at all -- they're just markings that are designed to alarm and deter potential predators. The insect's real eyes are sharp, but they are very small and hidden.

There are many kinds of click beetles, most of them small and brown and not nearly as noticeable as eyed click beetles. All of them, however, have the same unique ability: if they are flipped onto their back, click beetles can snap their thorax and abdomen together and with an audible click launch themselves up to a foot into the air. They don't always land on their feet, but if they don't they just wind up and try it again.

The Basics:

Scientific Name: Alaus Oculatus

Size: From a half-inch to nearly two inches

Habitat: Virtually any wild or green area

Range: Throughout the world

Notes: There are many, many species of click beetles in the world, and they can all snap themselves into the air to escape danger.

Late in a midwestern summer, when goldenrod is at its peak, soldier beetles can be the most common insect among the swarm of bees, flies, and butterflies trying to get as much nutrition as possible as the cool evenings set in. There are several kinds of soldier beetles, but they are all elongated and brightly colored, with leathery wing covers (elytra) instead of the usual hard shells found on most beetles. One explanation of their common name is that one of the first described species was patterned a a way that reminded the scientist of the red coats of British soldiers.

These beetles fly very well and are often mistaken for wasps, which is the idea -- they are completely harmless, but the way they buzz around flowers, showing their bright colors, may fool potential predators into thinking they can sting.

The Basics:

Scientific Name: Family Cantharidae

Size: Most are about an inch long

Habitat: Usually seen flying around flowers like goldenrod

Range: Throughout the Western Hemisphere

Notes: Soldier beetles resemble wasps, but they are harmless

Blister beetles are related to soldier beetles (above), and you can see the resemblance: they both have leathery, not shell-like, wing covers, and they both crawl over flowers during the day. Blister beetles are not always as brightly colored as soldier beetles, or the one pictured -- many are dark blue-black.

Blister beetles get their name from their body secretions, which can cause blisters on your skin. Gardeners often come in contact with them, and break out in itchy blisters later that night or the next day. It's likely that these toxic juices make the insect unpalatable to birds and other predators -- the bright colors of some species is a case of "aposomatic coloration," a bright color pattern that warns predators away.

The blistering quality of Cantharidae beetles is used in medicines for some skin conditions. It's also the basis for the legendary "Spanish Fly," a well-known aphrodisiac. Whether or not Spanish Fly actually works is beyond the scope of this article.

The Basics:

Scientific Name: Family Meloidae

Size: Most are about an inch long

Habitat: Usually seen climbing on low plants and visiting flowers, often in groups

Range: Throughout the Western Hemisphere

Notes: The blistering quality of their bodily oils has long been used for medical and recreational purposes.

Virtually everyone is familiar with these charming insects, which are of course not flies at all, but a kind of beetle with over 2,000 different species around the world. In the US, there are a number of species with very different habits, including one in which the females mimic the flashing call of the females of another species, luring the males; when the poor suitor comes calling, he is promptly dismembered and eaten. Like I said, charming.

Fireflies typically come out at night and find each other for mating -- or eating -- by means of a cold chemical flashing signal. The light they produce has no infrared or ultraviolet frequencies, completely different from sunlight. They are found throughout the world, and are known as "glowworms" in Eurasia and elsewhere.

The Basics:

Scientific Name: Family Lampyridae

Size: Most are about an inch long

Habitat: Anywhere with grass or other greenery

Range: These insects have a world-wide range

Notes: These beetles use cold, chemical light to attract mates and prey

This is a really cool and beautiful beetle, one which most people never encounter until one turns up dead one the porch or in the garage. The reason you likely won't see a live one is that they are both nocturnal and extremely fast, adapted to hunting, killing and eating other insects. Think of them as the T-Rex of the insect world.

If you do manage to corral a live C. scrutator, you may want to wash your hands. This insect has a chemical defense system that squirts noxious fluid onto attackers. The fluid smells like rotten milk or old socks, depending on who you ask. Best to leave these little beasts be.

The Basics:

Scientific Name: Calosoma scrutator

Size: Quite large; some specimens approach two inches in length

Habitat: Wild areas with caterpillars and other insects to hunt

Range: Throughout the eastern US

Notes: This is one of many beetles that use a chemical defense to escape predators.

The abilities of this little insect defy belief, and in fact have been put forward by creationists and other non-scientific theorists as evidence of everything from intelligent design to extraterrestrial origins of life on earth. Science begins with a question and seeks answers, and non-scientific approaches tend to begin with a belief or faith and concoct explanations from there. Given time, the scientific method brings us to an increasing understanding of how the world works, as it has for over a hundred years.

Meanwhile, bombadier beetles are busy combining two caustic chemicals in a special chamber of their body, letting it heat to the boiling point, and then shooting the boiling mixture with a pop out of their tail end straight into the face of whoever is harassing them. They can kill other insects this way, and cause discomfort and even burns to humans. If you find one of these little guys, by all means prod it into unleashing its cannon -- it's a singular example of evolution's power of innovation.

The Basics:

Scientific Name: Family Carabidae, in the tribes Brachinini, Paussini, Ozaenini, and Metriini

Size: Small ground beetles, often with black and red coloration

Habitat: On the ground in wild areas

Range: Throughout the world

Notes: Bombadier beetles possess one of the most effective, and mind-blowing, defense mechanisms in the entire animal kingdom

We'll end this guide with perhaps the most iconic and well-known of all beetles, the ladybug (or ladybird if you're in Europe). There are many, many species of ladybug, some of them very small and secretive insects that you will likely never see, and some of them familiar to almost everyone. The black-dots-on-red variety is what most people picture when they think, "ladybug."

Gardeners are likely at least somewhat familiar with this group's natural history, since they are considered beneficial in the control of aphids, little green insects that occur in colonies and can literally suck the life out of a plant. Ladybugs lay their eggs on or near aphid colonies; the larvae hatch out and spend their lives chowing down on aphids young and old. You have seen them if you're outside much at all, but maybe never made the connection with the adult beetle -- they look like miniature lizards. And they're a very effective aphid-control machine. The adults eat aphids, too. If you know you have an aphid problem, you can find ladybug eggs for sale on gardening sites.

These beetles, like all the beetles in this guide, are part of a complex and ancient web of predation and prey that is under serious attack from you and me. Awareness of the variety, beauty, and vulnerability of the life on this beautiful planet is the first step to undoing the damage we have done.

The Basics:

Scientific Name: Family Coccinelidae

Size: Small, rounded beetles, usually less than a half-inch in diameter

Habitat: In nearly every wild area

Range: Throughout the world

Notes: These beetles are a valuable natural control method in the fight against aphid infestations

The following sources were consulted for this guide:

https://www.insectidentification.org/beetles

http://texasento.net.Dynastes.htm

https://www.thespruce.com/keeping-weevils-away-from-food-256438

https://www.entomology/umn.edu

All images public domain