Beetles are the most diverse group of insects on Earth, with over 400,000 known species, and their diets are just as varied. Some eat leaves, some hunt other insects, some feed on dead animals, and others bore through the wood in your home. What a beetle eats depends entirely on its species, but broadly, beetles fall into a few major feeding categories: plant eaters, predators, decomposers, and scavengers.
Plant-Eating Beetles
The largest group of beetles are herbivores. Leaf beetles and weevils are almost exclusively plant feeders, making them some of the most prolific chewers in the insect world. Their strong, biting mouthparts let them slice through leaves, stems, roots, flowers, seeds, and fruit. Longhorn beetles, a family with over 20,000 species, feed primarily on wood. Their larvae tunnel through tree trunks and branches, digesting the tough cellulose fibers that most animals can’t break down.
Some beetles have evolved clever workarounds for digesting difficult plant material. Ambrosia beetles, for example, don’t actually digest wood directly. Instead, they cultivate a special fungus that liquefies woody tissue, then eat the fungus. It’s essentially farming at a microscopic scale. Other species skip the tough stuff entirely and feed on nectar and pollen, visiting flowers much like bees do.
Predatory Beetles
Not all beetles are vegetarians. Ladybugs (lady beetles) are among the best-known predators in the insect world, and their appetite is impressive. A single ladybug eats roughly 50 aphids per day and can consume around 5,000 aphids over its lifetime, according to the University of Kentucky Extension Service. Different ladybug species specialize in different prey: some target aphids, others feed on scale insects, and one group has specialized entirely on plant-feeding mites.
Some ladybug species are more flexible. The pink-spotted lady beetle eats a wide variety of prey alongside non-prey items like pollen and plant fluid. Ground beetles are another major predatory group, hunting slugs, snails, caterpillars, and other soil-dwelling invertebrates at night. Great diving beetles take predation underwater, using powerful jaws to catch aquatic insects and even small fish. Both the larvae and adults are active hunters.
Decomposers and Scavengers
Some of the most ecologically important beetles eat things most animals won’t touch: dung, dead animals, and rotting plant material.
Dung beetles feed on animal waste, rolling it into balls and burying it underground where they lay their eggs. Their larvae then feed on the buried dung as they develop. Carrion beetles play a similarly vital role by consuming dead animals. Burying beetles locate small vertebrate carcasses, bury them several inches underground, and feed on the decomposing tissue. Their larvae stay with the carcass for three to four weeks, eating the body as it breaks down into a soft, pasty mass.
Skin beetles arrive later in the decomposition process, feeding on dried skin, fur, and feathers. They’re so reliable in this role that forensic scientists use their presence to estimate how long a body has been dead. Hide beetles and their relatives scavenge old, dry carcasses and will eat anything remaining except bone. Some species have adapted to life in mammal burrows or bird nests, where they feed on shed fur, feathers, and other animal debris. A few eyeless cave-dwelling species survive by scavenging bat droppings.
Beetles That Eat Your Home and Food
Several beetle species have become household pests because their natural diets overlap with human-made materials. Powderpost beetles attack hardwood products like oak, ash, walnut, hickory, and cherry. Infestations commonly show up in flooring, paneling, molding, window frames, door frames, and furniture. Items made from bamboo are especially vulnerable. One group of powderpost beetles, the anobiids, prefers moist wood and can seriously damage structural beams and joists in buildings.
Pantry beetles target stored food. Flour beetles, grain beetles, and related species infest flour, cereal, grains, seeds, nuts, spices, and pet food. Foreign grain beetles take a different approach: rather than eating the food itself, they feed on the molds and fungi that grow on poorly seasoned lumber or damp plaster and wallboard. Carpet beetles, close relatives of the skin beetles that feed on animal carcasses in the wild, eat wool, silk, leather, and other animal-based fibers indoors.
How Diet Changes With Life Stage
Many beetles eat completely different foods as larvae than they do as adults. Longhorn beetle larvae spend years boring through wood inside tree trunks, but adults often feed on pollen, bark, or leaves. Some adult beetles don’t eat at all, living just long enough to mate and lay eggs. Ladybugs are an exception to this pattern: both the spiny, alligator-shaped larvae and the familiar dome-shaped adults are active aphid predators.
This dietary shift between life stages makes sense when you consider that beetle larvae and adults have very different body shapes, habitats, and nutritional needs. Larvae are growing machines that need calorie-dense food, which is why so many bore into wood, roots, or seeds where nutrients are concentrated. Adults need energy mainly for flying and reproducing, so lighter foods like nectar and pollen are often enough.