The red ant, most notably the highly successful Red Imported Fire Ant (Solenopsis invicta), has a reputation as an aggressive invader, and its complex diet is a major contributor to this success. These insects are not picky eaters; they function as highly efficient, generalist omnivores whose feeding habits are synchronized with the colony’s reproductive needs. The variety of food they consume allows them to dominate ecosystems and establish massive colonies across a wide range of environments. Their diet is a sophisticated mixture of proteins, fats, and carbohydrates, all processed and distributed through unique biological mechanisms.
The Omnivorous Diet of Red Ants
Red ants maintain a diverse diet that supports all stages of colony life, classifying them as opportunistic omnivores and scavengers. Proteins are secured primarily through predation and scavenging of other arthropods, including insects, spiders, and even small vertebrates like reptiles or newly hatched birds. In the presence of human activity, they readily consume meat scraps and pet food, which offer concentrated protein sources.
Fats and lipids are also highly sought-after, offering dense energy reserves crucial for colony maintenance. Fire ants are notably attracted to greasy substances, such as lard, cooking oils, and the oils contained within seeds. They also harvest plant-based carbohydrates, which provide the quick energy needed for foraging workers. This includes consuming plant exudates, nectar, and the sugary secretion known as honeydew, which they collect from sap-feeding insects like aphids.
The specific balance of this diet changes throughout the year based on the needs of the colony. During spring and summer, when the queen is laying large numbers of eggs and the colony is growing, the demand for protein increases significantly to support larval development. Conversely, adult workers require a consistent supply of carbohydrates and lipids year-round to fuel their high-energy activities.
Foraging Strategies and Prey Capture
The red ant’s method for obtaining food is aggressive and organized. Foraging workers rely on chemical communication, using pheromones to mark trails and recruit nestmates when a substantial food source is located. This recruitment allows them to quickly overwhelm and dismember items much larger than a single ant could manage alone. Workers are most active when ambient temperatures are optimal, generally between 70° and 90°F.
When attacking live prey, red ants employ a potent venom delivered via a painful sting to rapidly immobilize their victim. This venom contains piperidine alkaloids, known as solenopsins, which are used both for defense and for subduing struggling prey. For solid items too large to be moved intact, the workers cooperatively cut the food into smaller, manageable fragments. These small pieces are then transported back to the nest to be processed by the colony.
Internal Food Processing and Trophallaxis
The consumption and distribution of food within the colony involves a complex biological system adapted to the ant’s anatomy. Adult worker ants are physically unable to ingest solid particles, as their digestive tract has a filtering mechanism that screens out material larger than about 0.88 microns. Consequently, adult workers must subsist entirely on liquid nutrients.
The critical task of digesting solid proteins and fats falls exclusively to the colony’s oldest larvae, specifically the fourth instar stage. Workers will place solid food fragments near the mouth of these larvae, which then regurgitate digestive enzymes onto the food item to liquefy it. Once the protein or fat is broken down, the larvae ingest it and later regurgitate the processed liquid nutrients to the adult workers.
This liquid exchange system among colony members is known as trophallaxis, a mouth-to-mouth sharing process fundamental to red ant society. Trophallaxis ensures that the queen, the developing brood, and non-foraging workers receive a constant supply of nutrients. This social feeding network also serves as a communication highway, distributing pheromones and chemical signals throughout the colony.