The concept of a biological colony challenges the notion of a single organism, presenting life organized into cooperative, multi-individual units. Measuring the scale of these collective societies is not a uniform task, as the definition of “size” shifts dramatically across different kingdoms of life. A colony’s scale can be quantified by counting individuals, measuring total living weight, or determining the physical area it occupies. The immense variation in colonial organization, from a few dozen insects to vast fungal networks, requires diverse metrics to capture the dimension of social life.
Defining the Biological Colony
A biological colony is a cohesive group of organisms of the same species that live in close association, often displaying coordinated behaviors and interdependence. The defining feature is a functional integration that benefits the group’s survival and reproduction.
This organization falls along a spectrum, from simple clonal colonies to complex eusocial societies. Clonal colonies, such as those formed by bacteria or certain plants, consist of genetically identical individuals arising from a single parent. Eusocial colonies, characteristic of ants and bees, involve a reproductive division of labor, cooperative brood care, and overlapping generations, functioning as a single collective entity often termed a “superorganism.”
Metrics for Measuring Colony Scale
Quantifying colony scale requires adopting the appropriate metric for the organism. For social insects and other unitary animals, the most intuitive metric is the individual count, expressing population size in the number of workers or zooids. Conversely, for microorganisms and fungi, size is often expressed as biomass, measured in dry weight or total carbon mass per unit area, such as grams per square meter.
Physical area or volume is the standard for organisms that spread across a landscape or form massive structures. This metric captures the scale of subterranean or marine colonies, using measurements like square kilometers or hectares. For many clonal organisms, researchers also use “genetic size,” defining the extent of a single, interconnected genetic network that may span a vast territory.
Scale and Variation in Social Insect Colonies
Social insect colonies exhibit a vast range in scale, varying from small, temporary groups to continental megastructures. Colonies of primitive ants, such as Temnothorax, often contain only a few dozen to a few hundred individuals, typically nesting within small cavities. This contrasts sharply with mature colonies of species like fire ants or honeybees, which maintain populations ranging from 40,000 to 500,000 individuals in a single nest.
The largest scale is achieved by unicolonial species that form supercolonies, dissolving the boundaries between hostile neighboring nests. For example, the Argentine ant supercolony in Southern Europe was a network that stretched over 3,700 miles along the Mediterranean coast, estimated to contain billions of workers. Physically, the structures created by social insects can be immense; certain African termite mounds have reached heights of 41 feet, and subterranean ant nests form complex, multi-chambered cities deep underground.
Beyond Insects: Microbial and Marine Colonies
Colony scale extends beyond insects into environments dominated by microbial networks and vast marine structures. The largest organisms by sheer mass and area are often clonal colonies. For example, the Armillaria ostoyae fungus in Oregon spans 9.1 square kilometers and is estimated to weigh up to 35,000 tons. This fungal network exists primarily underground as an interconnected web of mycelium, illustrating a scale measured by both area and biomass.
Marine organisms also form immense structures, typically measured by physical dimension. Colonial animals called siphonophores, composed of specialized, genetically identical zooids, can trail through the water for lengths exceeding 46 meters, making them longer than a blue whale. Hard coral colonies, built by millions of tiny polyps, form massive, dome-shaped structures; some large Porites species have been recorded with circumferences of nearly 69 meters.
Microbial biofilms are dense, surface-attached communities of bacteria, ranging from a few micrometers to a millimeter in thickness. Massive microbial mats can cover vast swathes of the ocean floor, sometimes spanning an area comparable to a large country.
Constraints on Colony Growth
Despite the immense sizes achieved by colonial organisms, upper limits are imposed on growth. Resource availability is a primary constraint, as a colony must secure enough food and water to support its growing population. For instance, the expansion of a fungal network is limited by the availability of organic material in the soil.
Logistical challenges within the colony create bottlenecks as size increases. In large subterranean insect nests, the distance between foraging workers and the central brood can strain communication efficiency and resource transport speed. Furthermore, density-dependent factors, such as the rapid spread of disease or the accumulation of waste products, intensify in crowded colonial settings. This creates a functional trade-off where the benefits of a larger population are eventually outweighed by the increasing costs of internal maintenance and logistical complexity.