Ants
Like humans, ants have had an immensely complex and varied social evolution. It has culminated in the great ant societies with populations of a million or more individuals per colony. Frequently these colonies include specialized castes of workers and soldiers. They often support a variety of parasites and camp followers. Some herd other insects. Some enslave one another. ~ American entomologist Caryl Haskins
Ants evolved from vespoid wasps 110–130 MYA. Along with the rise of flowering plants, ants diversified, and gained ecological dominance 60 million years ago. In the process, finding strength in numbers, they left their wasp roots of solitary existence to live in gregarious eusocial colonies.
Ant success is spelled in multitudes. There are likely at least 1015 ants alive at any moment, with 22,000 extant ant species.
Ants have colonized almost every landmass on the planet, excluding only Antarctica and a few other remote or inhospitable locales, such as Greenland, Iceland, and the Hawaiian Islands.
Ants are superb ecosystem engineers. ~ English biologist David Edwards
The most abundant insects in the rainforest are ants, with quite different habitats. Some live on trees, in nests of leaves woven together. Others build subterranean caverns to nest in. A few find a home in rotten wood.
Army ants nest nowhere. They are relentlessly on the move, briefly resting in bivouacs.
South American leafcutter ants may destroy more foliage than all other creatures put together. Other ants have more benign, even beneficial, relations with plants.
Some seeds are structured to allure ants into carrying them away. While many such seeds are eaten, some survive to sprout far from where they were picked up, thus aiding floral distribution.
The rainforest is an ant mosaic. Almost all other animals are influenced by ants. Some are harbored and protected. Many more are attacked and eaten.
Ant success comes from adaptability: the ability to solve complex problems via swarm intelligence, coevolution with other species, and a highly developed social organization.
Though social complexity varies considerably, ants are uniformly eusocial insects. Isolated ants die of loneliness.
Ant colonies consistently differ in coping style—some are more risk-prone, whereas others are more risk-averse. ~ American behavioral biologist Sarah Bengston & German biologist Anne Dornhaus
Castes
Several ant species have colonies with multiple phenotypic castes. By creating specialists, a caste system optimizes social organization. Individuals are caste-bound via histone modifications, an epigenetic mechanism.
Even ant species that don’t physically specialize have functional roles. 3 castes are common: nurses, cleaners, and foragers.
Ants in different castes cluster together, rarely interacting with ants in other groups. Nurses that tend to the queen and brood spend their time deep within the nest, while foragers hang out near the nest entrance.
Cleaners are an exception. Roaming throughout the nest as part of their duties, cleaners interact with other cliques.
Ants commonly change careers as they get older. Typically, nurses graduate to nest cleaning. Cleaners transition to foraging as they age.
Career by age is not clear-cut. There are young foragers and old nurses. As with bees, aptitude and inclination play a role in the role that an ant plays within her colony. Every ant has her own personality.
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Ground-dwelling ants have a massive genomic database dedicated to sensory reception that matters most: 400 genes for odor, and 116 for taste. A honeybee has 179 genes for odor and 76 for taste.
Harvester ants are exemplary in efficient foraging. They avoid congestion and maximize gathering by allocating resources based upon feedback loops.
A harvester ant is slow to return to the nest unless it finds something. The faster foragers return, the more ants are sent for seeds in the same direction.
If returns become tardy, or without produce, the supply line is thinned, or the search called off. Ants leave pheromone trails that allow timing studies for foraging efforts. In sum, ants are efficiency experts.
A critical aspect of efficiency is resource allocation. A sizable minority of ants at any one time aren’t up to much, while a small minority do most of what is being done.
30% of the fire ants digging a tunnel may do 70% of the work. There may be many ants nearby (but out of the way), slacking off. The reason: avoiding getting in each other’s way.
Ants know that traffic jams greatly impede efficiency. If an active worker wants a break, she is instantly replaced. A surplus labor force as practiced by ants is the most productive and the most accommodating to worker wants and needs. Some ants are industrious, others not so much.
Collectively carrying a large load requires a high degree of coordination. One facet of this coordination is the requirement to align forces such that inefficient tug-of-wars are avoided.
~ Israeli myrmecologist Ofer Feinerman et al
Ants can carry large, heavy objects to their nest because they intelligently coordinate.
While the combined force of the group determines the speed of the load, individual informed ants steer the direction of movement. ~ Ofer Feinerman et al
