Odorous House Ant

The odorous house ant, Tapinoma sessile, is a Dolichoderine ant within the family Formicidae. Workers are monomorphic, ranging from 2.4 to 3.3 mm in length, characterized by their dark brown to black coloration and a flattened body profile with a single, hidden petiole node. Colonies are typically polygynous, housing multiple queens, and can range in size from a few hundred to over 100,000 workers, with queen numbers often in the hundreds. Queens have a lifespan of several years, while workers live for approximately 2-3 months. Reproduction occurs through budding, a process where a subset of the colony, including queens, workers, and brood, detaches to form a new colony, often in close proximity to the original nest. This species exhibits a high tolerance for varying environmental conditions, thriving in temperatures between 20-30°C and moderately humid environments, contributing to its widespread distribution across North America.

Tapinoma sessile exhibits primarily diurnal foraging activity, though they can forage at night, especially indoors or during warmer periods. They are highly adaptable in their social structure, transitioning from monodomous to polydomous colonies as they grow or encounter resource limitations. Communication within the colony relies heavily on chemical signals, with workers using trail pheromones for recruitment to food sources and alarm pheromones when disturbed, which is why crushing them releases a characteristic rotten-coconut smell (attributed to methyl ketones like 2-hexanone and 2-heptanone). They are omnivorous generalist feeders, with a strong preference for sugary substances, honeydew from aphids and mealybugs, and also consume protein sources like small insects and pet food. While not directly damaging to structures, their foraging activities can contaminate food storage areas and their prolific nesting can become a nuisance, particularly in sensitive environments like hospitals or food processing plants. They do not sting, but can bite, though this is rare.