Most ants are omnivores, and their diet runs on two fuels. Sugary liquids like flower nectar and aphid honeydew power the adult workers, while protein from insects and other animal matter goes mainly to the growing young.1PubMed. Communal nutrition in ants Some species have gone well past that basic menu, farming fungus, harvesting seeds, or hunting a single kind of prey.
Why Ants Need Both Sugar and Protein
Adult workers mostly burn carbohydrates, while protein is eaten mainly by the larvae.2PubMed. Communal nutrition in ants Foragers pick up signals from both hungry adults and hungry young when they choose what to bring home.3PubMed. Communal nutrition in ants Given a choice, ants tend to prefer food that leans toward sugar.4PubMed Central. Seasonality Directs Contrasting Food Collection Behavior and Nutrient Regulation Strategies in Ants Demand for protein climbs early in the season, when colonies are busy raising young.5PubMed. Different feeding preferences for macronutrients across seasons and sites indicate temporal and spatial nutrient limitation in the black bog ant
You can often see this split in the kitchen. Ants clustered at a sugar spill are workers refueling and gathering energy for their nestmates. Ants hauling off a dead insect or a meat crumb are collecting protein for larvae. Both behaviors can come from the same colony, so they don’t mean two kinds of ants.
A sugar-only bait or a single test crumb can mislead you. To learn what a colony wants right now, put out a small dab of honey and a small dab of something fatty or meaty, such as peanut butter or cooked egg, a few inches apart. Watch which one draws more traffic over an hour or two. The result is only a snapshot, because what foragers favor changes as the colony’s needs change.
Ants take in food in two ways. Solid food is cut and chewed with the jaws before it’s swallowed, while liquids are licked or sucked up directly with the mouthparts and a sucking pump.6PubMed Central. The feeding apparatus of ants: an overview of structure and function
Nectar and Honeydew The Sugar Ants Seek
Plants offer sugar well outside their flowers. Many have nectar glands on their leaves or stems that ants visit. On broad beans, garden ants tend both the nectar glands at the base of the leaves and black bean aphids.7PubMed. Interactions between extrafloral nectaries, aphids and ants: are there competition effects between plant and homopteran sugar sources? They usually ignore a second aphid species on the same plant.8PubMed. Interactions between extrafloral nectaries, aphids and ants: are there competition effects between plant and homopteran sugar sources?
Aphids supply sugar of their own. They feed on plant sap and release the extra as honeydew, a sugary liquid. When an aphid group is small, ants mostly drink plant nectar and barely tend the aphids.9Ecological Research. Why do ants shift their foraging from extrafloral nectar to aphid honeydew? As the group grows, the ants abandon the nectar and focus on the aphids.10Ecological Research. Why do ants shift their foraging from extrafloral nectar to aphid honeydew? The number of ants at a source tends to track how much sugar it produces.11Ecological Entomology. Foraging rate of ants collecting honeydew or extrafloral nectar, and some possible constraints
Gardeners see the result as a line of ants marching up a stem, which often leads to an aphid cluster. The ants protect the aphids from predators in exchange for honeydew. Defending them from enemies such as ladybug larvae gives the aphids a better chance to survive and keep producing.
To read the traffic, follow the line and check under the leaves and around the growing tips, where aphids tend to cluster. Sticky, shiny leaves or a dark sooty coating below the cluster are signs of honeydew building up. A few wandering ants may just be scouts or nectar drinkers, but a steady two-way line suggests a food source worth defending. Heavy traffic can be one clue to a growing aphid problem, and controlling the aphids often reduces the ants on that plant. Most ants on plants are drinking sugar, not chewing leaves; damage usually comes from the aphids.
Hunters and Raiders That Eat Other Animals
Army ant raids send thousands of workers across the forest floor hunting invertebrates.12Ecosphere. Hunting habits die hard: Conserved prey preferences in army ants across two distant neotropical rainforests Most army ant species mainly raid other ants’ nests, though swarm-raiding species take more non-ant prey.13Ecosphere. Hunting habits die hard: Conserved prey preferences in army ants across two distant neotropical rainforests A column of hundreds of army ants can paralyze or kill a worm nearly 16 inches long.14UW News. Ability to capture large prey may be origin of army ants’ cooperative behavior
A raid moves as a broad front or a set of columns, flushing and overwhelming prey that can’t escape. These raids are mostly a tropical sight, so you won’t usually see one in a temperate yard.
Other hunters are far more selective. Some ground-nesting ants hunt only one type of prey and have specially shaped jaws for it.15PubMed Central. The predatory behavior of ants: an impressive panoply of morphological adaptations Many are termite hunters, especially in the tropics.16PubMed Central. The predatory behavior of ants: an impressive panoply of morphological adaptations One African ant lives inside termite mounds and eats almost nothing but its hosts, yet it can learn to catch other termites when exposed to them.17PubMed. Predatory behaviour in the ponerine ant, Centromyrmex bequaerti: a case of termitolesty Many generalist ants also eat termites opportunistically.18PubMed. Ant-termite interactions: an important but under-explored ecological linkage
Group hunting is what lets small ants take on big prey. Workers recruit nestmates when they find plenty of prey, and they pile up paralyzed termites before carrying them home.
In the backyard, ants dragging caterpillars or beetles are hunting or scavenging protein. Ground ants help keep soil and leaf-litter insects in check.
How Ants Share Food Inside the Nest
Many ants never leave the nest, yet they eat. Foragers store liquid food in a storage pouch ahead of the true stomach.19PubMed Central. Ant trophallactic networks: simultaneous measurement of interaction patterns and food dissemination They bring it back up and pass it mouth to mouth to other ants, so the pouch works as a social stomach for the whole colony.20PubMed Central. Ant trophallactic networks: simultaneous measurement of interaction patterns and food dissemination Workers can also control what larvae are fed.21PubMed Central. Innovation in ant larval feeding facilitated queen–worker divergence and social complexity
A forager returns with a full pouch and meets a nestmate, who begs by touching the forager with her antennae and front legs. The forager brings up a droplet and passes it over, and the receiver can pass it on again. That’s how food reaches the queen and the workers tending the young. Two ants touching mouths are usually sharing food, and a forager’s abdomen can look swollen after drinking.
This matters for ant bait. A few foragers can spread liquid food to many nestmates, which is why slow-acting liquid baits can reach the queen. Fast-killing sprays mostly hit the foragers you can see.
Fungus Farmers The Leaf-Cutter Ants
Leaf-cutter ants cut leaves but don’t eat them. They grow a fungus on plant material gathered from many plant species.22PubMed Central. The fungal cultivar of leaf-cutter ants produces specific enzymes in response to different plant substrates The fungus digests the fresh leaves the ants deliver and turns the plant nutrients into small swellings that the ants eat.23PubMed Central. From Plants to Ants: Fungal Modification of Leaf Lipids for Nutrition and Communication in the Leaf-Cutter Ant Fungal Garden Ecosystem
Workers cut leaf pieces and carry them to the nest, where they clean and chew them into a mulch before adding it to the fungus. The fungus grows on this prepared material, which is why the ants need a steady supply of fresh leaves. They also remove unwanted molds.
You’d meet these ants in the warm parts of the Americas. Their trails carry leaf pieces into large underground nests, and where they occur they can strip garden plants quickly.
Seed Eaters and Seed Planters
Some plants give their seeds a fatty attachment, and ants eat it.24Xerces Society. Myrmecochory: How Ants Shape Plant Communities They carry the whole seed underground and eat only that attachment.25Xerces Society. Myrmecochory: How Ants Shape Plant Communities It contains an oily acid that attracts ants, and the seed itself lacks it, so seeds with the attachment were taken twice as often as seeds without.26Ecological Entomology. Switching roles from antagonist to mutualist: a harvester ant as a key seed disperser of a myrmecochorous plant About 95% of seeds carried home stayed alive to grow.27Ecological Entomology. Switching roles from antagonist to mutualist: a harvester ant as a key seed disperser of a myrmecochorous plant
A worker picks up the seed with the fatty attachment and carries it into the nest. Inside, the attachment is eaten or fed to larvae, and the seed itself is usually discarded. It ends up in a chamber or refuse area, still able to sprout.
Harvester ants normally store and eat seeds. With seeds that carry the fatty attachment, they can act as planters instead. Seeds left in nests sit in rich soil, away from seed predators. Woodland wildflowers like violets and trilliums often rely on ants this way.
Built-In Helpers Bacteria That Feed Ants
Some ants get missing nutrients from microbes. Amino acids are the building blocks of protein, and animals need certain ones their own bodies can’t make. Carpenter ants carry bacteria that supply amino acids missing from their food, so workers on a diet lacking those amino acids still raised as many young.28PubMed Central. Nutritional upgrading for omnivorous carpenter ants by the endosymbiont Blochmannia Plant-feeding turtle ants have gut bacteria that recycle waste nitrogen into amino acids.29PubMed Central. Herbivorous turtle ants obtain essential nutrients from a conserved nitrogen-recycling gut microbiome
This matters for ants on sugar-heavy diets, which are low in protein building blocks. Bacteria let some ants live on nectar and honeydew, and that helps explain why carpenter ants thrive on sweet foods. It doesn’t replace protein for larvae in most ants, though; partners extend the menu rather than rewrite it.
How Diet Shapes Queens and Workers
Food partly decides what a larva becomes. Larvae destined to be larger workers eat more protein-rich food than small workers, and future queens get the most nitrogen-rich diet of all.30PubMed. Caste determination in a polymorphic social insect: nutritional, social, and genetic factors Holding back protein keeps most larvae from becoming egg-layers.31Functional Ecology. The trophic ecology of castes in harvester ant colonies Other factors, including genes, also play a role.32PubMed. Caste determination in a polymorphic social insect: nutritional, social, and genetic factors
Larvae fed more protein-rich food grow larger, and size is a main difference between worker types. Adults decide how much and what kind of food each larva gets.
Seasons, Cities and Pest Ants
Ant diets shift with the calendar. Summer colonies gathered more food when what was on offer was unbalanced, while fall colonies did not.33PubMed Central. Seasonality Directs Contrasting Food Collection Behavior and Nutrient Regulation Strategies in Ants
City ants add human food to the menu. Pavement ants in New York carry a chemical signature matching fast food, and the more urban the area, the stronger that signature.34PubMed Central. Stable isotopes reveal links between human food inputs and urban ant diets Not all city ant species eat human food, though.35PubMed Central. Stable isotopes reveal links between human food inputs and urban ant diets Sugar can also fuel invasions: on Christmas Island, honeydew-fed invasive crazy ants reached huge numbers, because the extra sugar made colonies bigger, longer-lived and more aggressive.36Ecosphere. Carbohydrate supply drives colony size, aggression, and impacts of an invasive ant
At home, wipe up sugary spills and crumbs promptly. Seal pet food and greasy waste, since ants also seek protein. Match the bait type to what foragers are taking, and control aphids near the house to cut the honeydew supply.