Bugs eat an enormous range of things, from leaves and wood to blood, decaying flesh, and each other. With over a million described insect species on Earth, their diets span nearly every organic material imaginable. Roughly 38% of the world’s insects are herbivores that feed on living plants, 24% are detritivores that eat dead and decaying matter, 16% are predators, and about 14% are parasites that feed on or inside a living host. The rest are species whose larvae are fed by adults, like many bees and wasps.
Plant Eaters: The Largest Group
More insects eat plants than anything else. That 38% figure translates to nearly 350,000 known species, and they don’t all eat the same parts. Some chew leaves. Others bore into wood, mine tunnels inside leaves, suck sap through plant stems, or develop inside seeds. Caterpillars are classic leaf chewers, using powerful jaw-like mouthparts with flat grinding surfaces built for tough plant tissue. Aphids, by contrast, have needle-like mouthparts that pierce a plant’s vascular system and draw out sap. The greenbug aphid, a common wheat pest, actually injects a toxin while feeding that causes yellow, dying spots on leaves.
Fall armyworms illustrate how destructive plant-feeding insects can be. Their larvae eat corn, wheat, cotton, and grain sorghum. On young corn plants just two to three feet tall, they can kill the growing center of the plant, and on seedlings, the entire plant may die. On wheat, they eat plants down to the ground. These are chewing insects with sharp mandibles designed to slice through plant fibers quickly.
Predators That Hunt Other Bugs
Predatory insects have mandibles that are sharp-tipped with elongated teeth for capturing, piercing, and crushing prey. Assassin bugs, minute pirate bugs, damsel bugs, bigeyed bugs, and predatory stink bugs are some of the most common. Minute pirate bugs alone feed on spider mites, aphids, thrips, whiteflies, insect eggs, and small caterpillars. Assassin bugs take on leafhoppers, mealybugs, caterpillars, and more.
Praying mantises eat other insects and even small vertebrates like lizards and hummingbirds. Dragonflies catch mosquitoes and gnats mid-flight. Ladybugs can devour dozens of aphids per day. What unites these hunters is speed, specialized mouthparts, and often excellent vision. Many predatory insects are considered beneficial because they keep pest populations in check, and some, like minute pirate bugs and certain assassin bugs, are commercially bred and released for crop protection.
Blood Feeders
Mosquitoes, bed bugs, fleas, and sucking lice all feed on blood using piercing-and-sucking mouthparts that penetrate skin and draw fluid directly from blood vessels. Blood is a nutritionally unusual meal: very high in protein but low in fats and carbohydrates. These insects typically feed in large amounts but infrequently.
For many blood-feeding species, a blood meal isn’t just food. It triggers essential reproductive processes. Female mosquitoes need a blood meal to develop eggs. Without it, egg production stalls. This is why only female mosquitoes bite. Males feed on plant nectar instead. The same pattern holds for many biting flies: blood provides the protein required for egg development, while sugar from nectar fuels day-to-day energy needs.
Decay and Waste Recyclers
About a quarter of all insects eat dead and decaying material, including fallen leaves, rotting wood, animal carcasses, dung, and fungi. Termites and certain beetles are wood specialists, breaking down cellulose with the help of microorganisms in their guts. The elephant beetle of Central and South America, one of the largest insects alive, develops as a larva inside coarse woody debris on the forest floor.
Cockroaches are generalist detritivores. Oriental cockroaches eat decaying organic matter both indoors and out. Dung beetles feed on and bury animal feces, recycling nutrients back into the soil. Carrion flies lay eggs on dead animals, and their larvae consume the decomposing tissue. These insects play critical roles in breaking down waste and cycling nutrients through ecosystems, even though many of them, like cockroaches and certain flies, are treated as pests.
Liquid Feeders
Butterflies, moths, and house flies don’t chew at all. They consume only liquids, but they do it in very different ways. Butterflies and moths use a long, coiled tube called a proboscis to siphon nectar from flowers. This structure is so finely built that it can pull nanoscale amounts of fluid from tiny pores in a flower’s surface through capillary action.
House flies use a sponge-like mouthpart. They regurgitate digestive enzymes onto solid food, dissolve it, and then soak up the resulting liquid through spongy pads full of tiny channels. Bees use a lapping technique, trapping nectar in fine hairs on their mouthparts before drawing it inward. Each of these strategies reflects a different solution to the same problem: getting nutrition from fluids rather than solids.
How Ants Farm Their Food
Some insects don’t just find food. They cultivate it. Ants are the best-known example. Many ant species tend colonies of aphids the way ranchers tend cattle. Aphids suck plant sap and excrete a sugary waste called honeydew, and ants collect this honeydew as a major food source. For Argentine ants, honeydew can account for more than half of their total diet.
Honeydew is rich in carbohydrates and contains both essential and nonessential amino acids, making it more nutritionally complete than researchers once assumed. Carbohydrates from honeydew are especially important for ant larvae. In return for this food supply, ants protect aphids from predators. Ants on protein-poor diets benefit most from aphid access, and notably, they don’t eat the aphids themselves, preserving the relationship. Leafcutter ants take farming even further: they harvest pieces of leaves, carry them underground, and use them to grow a specific fungus that the colony eats.
What Household Bugs Are After
The bugs you find in your kitchen are after specific things. Pavement ants are strongly attracted to sweet foods, though they eat a wide range of scraps. Carpenter ants enter homes looking for food but also chew tunnels through moist or rotting wood to build nests (they don’t eat the wood like termites do). German cockroaches eat almost anything: crumbs, grease, soap, glue, even book bindings. American cockroaches are similarly unfussy. Pantry moths and beetles target stored grain products like flour, cereal, rice, and dog food.
What makes many household pests so successful is their flexibility. Cockroaches can survive on tiny amounts of organic residue, including the starch in wallpaper paste. Silverfish eat paper, fabric, and dried foods. This dietary versatility is why simply cleaning up visible crumbs often isn’t enough to eliminate an infestation. These insects evolved to exploit scattered, low-quality food sources, and a human home provides those in abundance.