Ants are opportunistic omnivores, foraging for carbohydrates, proteins, and fats to sustain their complex colonies. Carbohydrates, usually sugars, provide energy for worker activity. Proteins are crucial for larval development and the queen’s reproductive health. Understanding their diet is key to understanding their limitations, as not all encountered substances can be safely ingested or processed.
Physical Barriers and Indigestible Materials
Adult worker ants cannot ingest solid food because their digestive system is too narrow for solid particles to pass into the midgut. They consume only liquids, storing them in a specialized crop for transport back to the colony. Solid materials must first be broken down by the larvae, which process them into a liquid form that adults can consume.
This physical limitation prevents ants from deriving nutrition from substances that are structurally too complex or large to be manipulated into a liquid state. Complex plant fibers, such as cellulose, are largely indigestible by the ants themselves. Even in leaf-cutter ants, the fungus they farm does not appear to break down cellulose, suggesting structural plant material is not a primary nutrient source.
Extremely smooth surfaces, such as those coated in Teflon or specialized anti-climb resins (Fluon), create a physical barrier they cannot cross. The ants’ small tarsal claws cannot grip the low-friction surface. This makes vertical movement impossible, preventing access to food sources beyond the barrier.
Compounds That Are Toxic or Lethal
Certain common substances are lethal to ants, acting either as internal poisons or causing fatal physical damage. Diatomaceous Earth (DE) is a mechanical insecticide that kills through physical action rather than chemical toxicity. This fine powder is composed of the fossilized remains of diatoms, which are microscopic silica organisms. The particles have sharp, abrasive edges that scratch the ant’s waxy outer exoskeleton layer when they walk across it.
Damage to the exoskeleton causes the ant to rapidly lose internal moisture, leading to fatal desiccation. Diatomaceous earth is effective only upon direct contact and does not need to be ingested. In contrast, boric acid, often mixed with a sugary bait, operates as a slow-acting stomach poison. Once ingested, it disrupts the ant’s digestive system and metabolism, interfering with nutrient absorption.
The poison’s slow nature allows the foraging ant to carry the contaminated bait back to the nest. They share it with the queen and other colony members through trophallaxis. Baking soda (sodium bicarbonate) functions as another internal disruptor when mixed with an attractant like powdered sugar. When ingested, it reacts with stomach acids, producing carbon dioxide gas that ants cannot expel, leading to a fatal disruption of their pH balance.
Substances Ants Actively Repel
Many substances are not toxic or indigestible but possess volatile properties that interfere with ant communication and navigation. Ants rely on pheromone trails to guide their colony to food sources. Strong odors and acidic compounds effectively scramble these chemical messages, causing the ants to avoid the area.
White vinegar, an acetic acid solution, works by neutralizing and erasing these pheromone trails, making established paths impossible to follow. Similarly, essential oils like peppermint, tea tree, and citrus contain powerful aromatic compounds. These strong scents overwhelm the ant’s sensitive olfactory system, masking the pheromones and turning the communication system into chaotic noise.
Powdered spices, such as cinnamon, contain potent compounds that act as natural deterrents. The chemical trans-cinnamaldehyde in cinnamon is particularly effective at repelling ants. These substances serve as behavioral barriers, encouraging the ants to bypass the treated area entirely rather than attempting to consume or cross it.