What Do Beetles Eat

Short answer

• Beetles do not share one diet. Beetles are insects in the order Coleoptera, and different groups eat very different foods. Some eat leaves, roots, seeds, fruit, pollen, or nectar. Others hunt aphids, caterpillars, slugs, snails, tadpoles, or small fish. Still others eat fungi, decaying wood, carrion, or dung. In many species, the larva and the adult eat different foods, so the correct answer often depends on both the beetle group and its life stage. If you see a beetle and want to know what it eats, start with where it is and what it is doing. A beetle chewing a leaf is likely a plant feeder. A beetle running across soil at night may be hunting. A beetle on dung, carrion, or rotting wood is likely using that material as food or as food for its young. The sections below organize beetle diets by group.

By Emma Hudson

Why One Answer Cannot Cover All Beetles

Beetles are an unusually varied group. They live in soil, leaf litter, trees, flowers, ponds, streams, animal nests, stored food, and even inside other organisms. Their mouthparts reflect that range. Most beetles have chewing mouthparts, but the shape, strength, and use of those mouthparts differ. A leaf beetle needs jaws that can cut plant tissue. A ground beetle needs jaws that can seize and hold moving prey. A dung beetle needs mouthparts that can strain fine particles from dung. A diving beetle larva needs sickle shaped jaws that can pierce prey and take in liquid food.

Diet also changes with the job of each life stage. Larvae are mainly growth machines. They eat to build the body that will become the adult. Adults are mainly concerned with maintenance and reproduction. An adult may eat less, eat different food, or in some groups eat little or nothing at all. That is why a guide that lists only adult food can be misleading. A Japanese beetle adult and a Japanese beetle grub, for example, do not eat the same plant parts, even though they belong to the same species.

Terms such as herbivore, predator, scavenger, and omnivore are useful, but they are not fixed boxes for every beetle. Some are strict specialists. Others are broad feeders. A few switch between plant food and animal food. The most accurate approach is to name the group, describe its usual food, and note the exceptions that matter. This article follows that approach, and it avoids a common trap: assuming that a beetle found on a plant must be eating that plant. Some visit flowers for nectar or pollen, some hunt the insects that eat the plant, and some are only resting there.

Herbivores: Leaves, Roots, Seeds, Flowers, and Fruit

Plant eating beetles are common and easy to notice, because their feeding often leaves visible marks on leaves, flowers, or fruit. Many herbivorous beetles eat leaves. Leaf beetles, for example, chew holes in foliage or feed along leaf edges. Some specialize on one plant family. Others feed more broadly. The result can look like ragged chewing, small round holes, or, in the case of the Japanese beetle, tissue removed between the leaf veins while the veins remain. Colorado State University Extension describes that pattern as skeletonizing, and notes that Japanese beetle adults feed on leaves, buds, and flowers of many garden and landscape plants.

Roots are another major plant food, especially for larvae. Japanese beetle larvae are white grubs that feed on grass roots. That feeding can prune roots and reduce the ability of turfgrass to take up water. Many other beetle larvae also feed underground. Wireworms, the larvae of click beetles, feed on roots and seeds in soil. Weevils include many root feeders in the larval stage. The adult may look very different and may feed above ground, but the larva does much of its damage out of sight.

Seeds, fruit, and flowers attract a different set of plant feeders. Some beetles eat pollen and nectar and may help pollinate flowers while they feed. Others eat flower parts, developing fruit, or seeds. Grain beetles and other stored product beetles feed on seeds and dried plant material indoors, which is why they appear in pantries. Outdoors, seed eating beetles may feed inside seed pods or on fallen seed. Fruit eating beetles include flower beetles and fruit chafers that take ripe or soft fruit. Their feeding is often opportunistic: a beetle that normally eats pollen may also take juice from a damaged fruit.

Not all plant feeders are pests. Some feed on weeds or dead plant material, and others cause only minor damage. For identification, the plant part matters: leaf feeders, root feeders, seed feeders, and flower feeders are different roles, even when the beetles look similar.

Larva and adult differences are common among herbivores. A leaf beetle adult may feed on leaves while its larva mines inside a leaf, feeds on roots, or feeds on a different part of the same plant. A scarab adult may feed on flowers or fruit while its larva, a grub, feeds on roots or decaying plant matter in soil. Readers should therefore ask two questions, not one: what does the adult eat, and what does the larva eat. The answer to the second question often explains damage that the adult never causes.

Predators: Lady Beetles, Ground Beetles, and Other Hunters

Predatory beetles hunt other animals, usually small invertebrates. The best known examples are lady beetles, also called ladybugs or ladybird beetles. Most lady beetles are predators in both the larval and adult stages, although adults may also take pollen, nectar, or honeydew as a supplement. Colorado State University Extension notes that both adult lady beetles and their grub stage larvae have chewing mouthparts and are voracious predators of other insects. Their usual prey includes aphids, scales, spider mites, mealybugs, insect eggs, and other small arthropods that they can attack and ingest.

Not all lady beetles eat the same prey. Some specialize on aphids. Others specialize on scale insects or spider mites. The pink lady beetle, for example, feeds on aphids and also on Colorado potato beetle eggs and other soft bodied prey, and South Dakota State University Extension notes that its larvae typically consume more prey than adults. That detail matters for gardeners: a lady beetle larva, which looks nothing like the familiar spotted adult, may be doing much of the hunting. The Mexican bean beetle is an important exception. It is a lady beetle that feeds on plants, not prey, and it feeds on bean leaves and pods. The exception proves the rule that family alone is not enough: the exact species and its food preferences matter.

Ground beetles are another major predatory group. Washington State University describes ground beetles as ground dwelling beetles that live in soil and detritus, with some species preying on cutworms, ants, maggots, earthworms, slugs, and other beetles. Many ground beetles hunt at night and hide under stones, logs, or leaf litter during the day. They are fast runners with strong jaws. Some ground beetle larvae are also predators, and some use liquid feeding: they inject digestive fluids into prey and then take in the softened contents. That method is common in predatory beetle larvae and in some adult ground and rove beetles.

Tiger beetles are fast, visual hunters that chase prey on open ground. Soldier beetles may feed on other insects and also visit flowers for pollen and nectar, which makes them harder to place in one category. Firefly larvae are predators of snails, slugs, and worms. The National Wildlife Federation notes that firefly larvae eat snails, worms, and slugs, which they inject with a numbing chemical to disable, while adults eat other fireflies, nectar, or pollen, or in some species do not eat at all.

Predatory beetles are not all generalists. Some are narrow specialists that hunt one kind of prey. Others take any small animal they can catch. Size sets a limit: a small predator cannot take large prey, and a large predator may ignore prey too small to be worth the chase. Habitat also sets a limit. A beetle that hunts in soil will meet different prey from a beetle that hunts on leaves or in water. That is why the same feeding label, predator, can describe very different daily diets.

Scavengers and Carrion Feeders: Nature’s Cleanup Crew

Scavengers eat dead organic matter. That broad label covers several different jobs. Carrion beetles feed on dead animals. Hide beetles and skin beetles feed on dried animal tissue, feathers, fur, horns, and hooves. Dermestid beetles, the skin beetles used in museum collections to clean flesh from bones, feed on dried flesh and skin. The Smithsonian describes a dermestid colony that cleans flesh from specimens, a reminder that the same feeding habit can be useful in a museum and unwelcome in a home where it damages wool, leather, or stored specimens.

Other scavengers feed on decaying plant matter, fungi, and mixed organic debris. Darkling beetles include many scavengers that feed on decaying plant and animal material. Some beetles feed mainly on fungi, including mushrooms, molds, and yeasts mixed with plant sap. Fungus feeding beetles help break down dead wood and leaf litter, and some carry fungal spores to new sites. Their role is easy to miss because fungi are often hidden inside wood or under bark, but the feeding itself is part of normal decomposition.

Larva and adult diets in scavenger groups are often similar, but larvae often feed more intensively because they are growing. A beetle found on a dead animal may be feeding, laying eggs, or hunting the flies and maggots that also use the carcass.

Scavengers are often confused with pests, and sometimes they are pests. Carpet beetles, for example, are scavengers in nature, but indoors their larvae feed on wool, fur, feathers, and other animal fibers. That is the same feeding habit in a different setting. The beetle has not changed its diet. The setting has changed what the diet damages. Understanding the natural diet therefore helps explain indoor problems without turning every scavenger into a villain.

Wood Borers: Eating Wood, Fungi, and the Material Inside Trees

Wood boring beetles feed inside trees, branches, twigs, and timber. The University of California Statewide Integrated Pest Management Program notes that tree boring beetles bore into branches, twigs, and trunks, that adults lay eggs on or in the wood, and that larvae feed within it, often making distinctive tunnels or galleries. That life pattern is the key to wood borer diets: the adult may feed little, or may feed on leaves, bark, or nectar, while the larva does most of its feeding hidden inside wood.

Wood itself is hard to digest. Many wood boring beetles rely on fungi, bacteria, and yeasts in their digestive systems to help break down wood material. Some feed on the fungi growing inside wood rather than on the wood fibers alone. Others feed on inner bark, sapwood, or the nutrient rich layer just under the bark. Longhorn beetles, bark beetles, and jewel beetles include many wood feeders, but their exact food depends on the tree species, whether the wood is living or dead, and whether the beetle attacks healthy trees, stressed trees, or already dead timber.

Dead wood feeders break down fallen trees, open wood to fungi and other decomposers, and return nutrients to soil. Living tree feeders can be pests when they attack healthy trees, but many bark beetles mainly attack stressed or dying trees.

Larva and adult differences are strong in this group. A longhorn beetle larva may spend months or years tunneling through wood, while the adult lives only a short time and may feed on flowers, leaves, or sap. A bark beetle larva feeds in galleries under bark, while the adult bores a new entry tunnel to lay eggs. Anyone who finds only the adult on bark cannot safely assume that the adult eats wood in the same way as the larva. The tunnels are the larva’s feeding record.

Dung Beetles: Food, Housing, and Care for the Young

Dung beetles feed on dung, usually the dung of mammals, especially herbivores. The Missouri Department of Conservation notes that plant material is difficult for mammals to digest, and dung beetles capitalize on nutrients that pass undigested through a mammal’s digestive tract. It also notes that most dung beetles feed at least partly on dung, although some species eat carrion or fungi. That qualification matters: dung beetle is a useful group name, but it does not mean every species eats only dung.

Dung beetles are usually divided by what adults do with dung. Rollers shape dung into a ball and roll it away before burying it. Tunnelers dig beneath a dung pat and drag dung underground. Dwellers live and breed within the dung pat itself. In each case, the buried or stored dung serves two purposes: food for the adult and food for the larva. The Missouri Department of Conservation explains that the first objective of many adult dung beetles is not to feed themselves but to secure food for their larvae, which is why they bury and sometimes roll dung away, lay eggs inside the balls, and give the growing larvae a private supply that they do not have to share with competitors such as fly maggots.

Adult dung beetles feed by straining fine particles from dung. They use brush like mouthparts to take in liquid and small particles, including undigested plant material, bacteria, yeasts, and molds. Larvae feed inside the brood ball or tunnel on the stored dung until they pupate and emerge as adults. The adult and larva therefore eat the same broad material, but in different places and for different reasons: the adult feeds to survive and reproduce, while the larva feeds to grow, and the parent’s work of burying dung shapes the larva’s entire food supply.

By burying dung, dung beetles move nutrients into soil and reduce breeding sites for flies and parasites. That work follows directly from feeding and breeding.

Aquatic Beetles: Hunters and Scavengers Under Water

Aquatic beetles include two broad feeding patterns: predators and scavengers, with some groups mixing both. Predaceous diving beetles are the clearest predators. Britannica describes the family Dytiscidae as carnivorous aquatic beetles that prey on organisms ranging from other insects to fish larger than themselves, and notes that the family includes more than 4,000 species. That size range matters: a tiny diving beetle cannot take the same prey as a large diving beetle. Small species take insect larvae, worms, and small crustaceans. Large species may take tadpoles, snails, and small fish.

Diving beetle larvae are also predators, and they are often more formidable than the adults. They have large, sickle shaped mandibles and feed by piercing prey and taking in liquid food. Adults hunt by swimming and seizing prey with their jaws. Both stages may also scavenge dead aquatic animals when live prey is scarce. That flexibility helps them survive in ponds where prey abundance changes with season, water level, and the presence of fish.

Water scavenger beetles, by contrast, feed mainly on decaying plant and animal material in water. They may also take small live prey, but their main role is closer to that of a cleanup crew. Whirligig beetles feed at the water surface, taking small insects and organic debris trapped in the surface film. Other aquatic beetles feed on algae, aquatic plants, or detritus. EcoSpark’s beetle account notes that beetle larvae can be herbivores, scavengers, or predators, and that herbivorous larvae may eat aquatic vegetation such as algae, roots, and leaves. That range within one habitat shows why the word aquatic does not describe a diet on its own.

Larva and adult diets in aquatic groups can differ in prey size and hunting method even when both stages are predators. A diving beetle larva may ambush prey in one area, while the adult swims widely and chases prey. Different beetles also use different pond zones: surface, open water, vegetation, and bottom sediment.

How to Tell What a Beetle Eats Without Guessing

A reliable identification starts with observation, not with a guess from color or size. First, note the habitat: leaf, flower, soil, wood, dung, carrion, stored food, or water. Second, note the life stage: larva, pupa, or adult. A grub in soil, a larva in wood, and an adult on a leaf may belong to the same species, but they may eat different things. Third, note the feeding sign: holes in leaves, tunnels in wood, root pruning, a dung ball, or prey being seized. Feeding signs often survive after the beetle has left, and they can be more informative than the beetle itself.

Fourth, use the group as a guide, but check the species when possible. Lady beetles are usually predators, but the Mexican bean beetle is a plant feeder. Dung beetles usually eat dung, but some eat carrion or fungi. Firefly adults may eat nectar or pollen, eat other fireflies, or eat nothing at all, depending on species. A group label is a starting point, not a final answer.

Fifth, avoid two common errors. Do not assume that a beetle on a flower is eating the flower: it may be hunting aphids, taking nectar, or resting. Do not assume that a beetle in a house is eating house material: it may have wandered in from outdoors, or it may be hunting other insects inside. The safest statement is often the most specific one you can support: where the beetle was found, what it was doing, and what its group usually eats.

For gardeners, plant diversity, leaf litter, and undisturbed soil support a mix of plant feeders, predators, and decomposers. That mix is normal. A single beetle on a plant is not proof of a problem, and a predator on a plant may be helping by eating plant pests. If damage is severe or spreading, identify the species before acting, because the correct response depends on whether the beetle is a plant feeder, a predator, a scavenger, or only a visitor.

What Beetles Do Not Eat, and Why the Question Needs Care

Beetles do not eat everything, even though the group as a whole eats an unusually wide range of foods. A leaf beetle will not hunt fish. A diving beetle will not eat dry leaves as its main food. A dung beetle will not thrive on fresh green leaves alone. The breadth of beetle diets belongs to the order as a whole, not to any single species. That distinction is the most important correction to the simple question, what do beetles eat.

Beetles also do not all eat in the same way. Some chew solid food, some pierce prey and take in liquid, some strain fine particles from dung or detritus, and some rely on microbes to break down wood. A beetle may be surrounded by material it cannot digest, and that material is not food for that beetle, even if another group eats it readily.

Bees provide a useful contrast, without duplicating bee biology here. Bees are mainly flower visitors that collect nectar and pollen, and honey bees store food in a colony. Beetles, by contrast, include flower visitors, but also hunters, scavengers, wood feeders, and dung feeders, and most beetles do not live in colonies or store food in the way honey bees do. Readers who want bee diversity and honey making should read the separate Amberaisle articles on different kinds of bees and on how bees make honey.

FAQ

What do most beetles eat?

Most beetles eat plant parts, other small animals, fungi, or decaying organic matter, depending on their group. There is no single most common beetle food that applies to every species. Leaf, root, seed, and flower feeding are common among herbivores, while aphids, mites, insect eggs, and other small invertebrates are common among predators.

Do beetle larvae eat the same food as adults?

Sometimes, but often not. Many larvae and adults share a broad food type, such as dung or carrion, but differ in the plant part, prey size, or feeding location. In other groups the change is larger: a grub may feed on grass roots while the adult feeds on leaves and flowers, or a firefly larva may hunt snails and slugs while the adult feeds on nectar, pollen, or nothing at all. Always check both stages.

What do lady beetles eat?

Most lady beetles eat aphids, scales, spider mites, mealybugs, insect eggs, and other small soft bodied arthropods. Adults may also take pollen, nectar, or honeydew as a supplement. The Mexican bean beetle is an exception: it feeds on bean plants. Lady beetle larvae are also predators and often eat more prey than adults.

What do ground beetles eat?

Ground beetles are mainly predators. They eat cutworms, ants, maggots, earthworms, slugs, and other beetles, among other ground dwelling prey. Some also take plant material or decaying matter, but hunting is their main role. They usually hunt at night and hide under stones, logs, or leaf litter during the day.

What do dung beetles eat?

Dung beetles eat dung, usually from mammals, especially herbivores. They strain fine particles from dung, including undigested plant material and microbes. Some species also eat carrion or fungi. Adults bury dung as food for themselves and as a stored food supply for larvae, which feed inside brood balls or tunnels until they emerge as adults.

What do diving beetles eat?

Diving beetles are predators. Adults and larvae eat aquatic insects, insect larvae, worms, snails, tadpoles, small crustaceans, and, in larger species, small fish. They may also scavenge dead aquatic animals when live prey is scarce. Water scavenger beetles are different: they feed mainly on decaying plant and animal material in water.

What do wood boring beetles eat?

Wood boring beetle larvae feed inside wood, inner bark, or sapwood, often with help from fungi and microbes that break down wood material. Adults may feed on leaves, flowers, bark, or sap, or may feed little at all. The tunnels in wood are mainly the larva’s feeding record, not the adult’s.

Do beetles eat fruit?

Some beetles do. Flower beetles and fruit chafers take ripe or soft fruit, and some plant feeding beetles take fruit in addition to leaves or flowers. Other beetles found on fruit may be hunting insects, taking juice from damaged fruit, or only resting there. The beetle group and its behavior matter more than the location alone.

Are beetles that eat plants always pests?

No. Some plant feeding beetles cause serious damage, especially when they feed in large numbers or when larvae feed on roots. Others cause only minor damage, feed on weeds or dead plant material, or are part of normal plant communities. Predatory beetles on plants may actually help by eating plant pests. Identification to species is the safest step before judging a beetle as a pest.

How can I tell what a beetle in my garden eats?

Note where it was found, whether it is a larva or an adult, and what it was doing. Leaf holes point to leaf feeding, tunnels point to wood feeding, root damage points to grub feeding, and a dung ball or carrion visit points to scavenger or dung feeding. If the beetle is hunting small insects on a plant, it is likely a predator. When in doubt, identify the group first, then check the species, because exceptions such as the plant eating Mexican bean beetle exist.

Sources & references

• University of Michigan, BioKIDS: Critters, Coleoptera, What do they eat and What roles do they have in the ecosystem sections. Used for the broad claim that larvae sometimes eat different foods from adults, and that most beetles eat plant parts while many are predators, some eat fungus, and some eat dung.
• EcoSpark, Beetle (Coleoptera), Diet/Feeding section. Used for the claim that beetle larvae can be herbivores, scavengers, or predators, and that herbivorous larvae may eat aquatic vegetation such as algae, roots, and leaves.
• Colorado State University Extension, Lady Beetles. Used for lady beetle prey, larva and adult predation, adult pollen and nectar supplements, and the Mexican bean beetle exception.
• Colorado State University Extension, Japanese Beetle. Used for adult leaf, bud, and flower feeding, skeletonizing, and larva root feeding on grasses.
• Washington State University, Hortsense, Predatory Beetles. Used for ground beetle prey and habitat, and for lady beetle prey including mites, thrips, insect eggs, scales, and mealybugs.
• South Dakota State University Extension, Pink Lady Beetles: Beneficial Predators in Urban and Agricultural Landscapes. Used for pink lady beetle prey and the note that larvae typically consume more prey than adults.
• Missouri Department of Conservation, Field Guide, Dung Beetles (Tumblebugs). Used for dung as the main food, carrion and fungi as exceptions, and burial of dung as larva food.
• University of California Statewide Integrated Pest Management Program, Beetles: Pests of home, garden, landscape, and turf. Used for wood boring behavior, egg laying on or in wood, and larva feeding within wood.
• Britannica, Predaceous diving beetle (family Dytiscidae). Used for diving beetles as carnivorous aquatic beetles, prey range, and the family size of more than 4,000 species.
• National Wildlife Federation, Wildlife Guide, Fireflies. Used for firefly larva prey and adult diet variation, including adults that eat other fireflies, nectar, or pollen, or do not eat at all.
• Smithsonian Institution, Sidedoor, Meet the Beetles. Used for the general role of beetles in pollination, dung processing, pest eating, and dermestid beetles cleaning flesh from specimens.