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C Cooperation in Social Insects Consider a honey bee colony – perhaps the best known insect society (Winston 1987; Seeley Raghavendra Gadagkar 2010;Page2013). Their colonies comprise tens Centre for Ecological Sciences, of thousands of individual bees, among which Indian Institute of Science, Bangalore, India there is a single, large, and fertile female bee who is called the queen. Only the queen is mated, and with a store of sperm gathered Many species of insects, such as ants, bees, from many males during her nuptial flight at wasps and termites, organize themselves into the beginning of her life, she can lay thousands societies that parallel, and sometimes better, of eggs per day, both fertilized eggs that develop human societies. They have impressive levels of into females and unfertilized eggs that develop social organization, communication, division into males. Colonies may comprise a few male of labor, cooperation and conflict, altruism and bees, also known as drones. The proverbially lazy self-sacrifice, policing and punishment, and drones do not take part in social life and do not learning and teaching. They can accomplish contribute to domestic work. Instead, they leave feats in warfare with neighboring colonies or their nests of birth and attempt to mate with virgin feats of internal cooperation such as the construc- queens of other colonies. Drones successful in tion of sophisticated nests or mounds, which mating die in the act of copulation as their genitals are impossible for individual colony members. are severed from their bodies and left hanging They are organized into colonies whose sizes onto the females. The rest of the colony comprises range from a few individuals up to a million smaller nearly sterile female bees, called workers. or more, occupying from a few centimeters to Workers have lost their genitalia over evolution- hundreds of square kilometers (Fig. 1). ary time and cannot mate and cannot produce © Springer Nature Switzerland AG 2020 T. K. Shackelford, V. A. Weekes-Shackelford (eds.), Encyclopedia of Evolutionary Psychological Science, https://doi.org/10.1007/978-3-319-16999-6_1367-1 2 Cooperation in Social Insects Cooperation in Social Insects, Fig. 1 Examples of the paper wasp Ropalidia marginata; lower right, the tropical major eusocial insects. Upper left, the tropical weaver ant, mound-building termite (Odontotermes obesus). (Photos Oecophylla smaragdina; upper right, the Asian dwarf courtesy Dr. Thresiamma Varghese) honey bee Apis florea; lower left, the best studied Indian female offspring. They have small ovaries (much orderly, systematic fashion through a process smaller than those of the queen), but these usually known as age polyethism. Young bees begin by remain undeveloped in the queen’s presence. cleaning the nest, after which they successively Only upon the death of the queen and the colony transition to perform the tasks of building the nest, not being able to rear a new queen do some feeding the larvae, guarding the nest, and finally workers develop their ovaries and lay a few hap- venturing out to forage for pollen and nectar, loid, male-destined eggs. In the presence of a which serve as the sources of protein and carbo- healthy queen, workers refrain from reproduction hydrate, respectively, for the growing larvae. The and spend their whole lives working for the wel- task a bee performs depends on its relative age in fare of their colonies. Various tasks required for the colony. At the age at which they build the the functioning of the colony are performed in an nest, they have active wax glands that convert Cooperation in Social Insects 3 the nectar consumed into wax, which is used specific information about the distance and direc- for building the nest. As the worker bees get tion of the food source. Bees estimate the distance older, these wax glands degenerate, and their and direction of the food source by the image hypopharyngeal glands develop instead, secret- motion on their eyes of the surrounding landscape ing, many substances that are added to the diet (optic flow) and a process of dead reckoning of the larvae. Such relative age-based polyethism called path integration, keeping track of their has a built-in flexibility permitting the colony to successive linear and angular displacements as adaptively respond to unexpected changes they meander on their outward search flights in demography. Upon experimental removal of (Wehner 1992, Mandal 2018). Worker bees thus old bees, the relatively older of the intranidal devote their whole lives to the welfare of their workers becomes precocious foragers, leaving colony and do not reproduce, even in the form the nest at an abnormally younger absolute of a few male-destined eggs that they can poten- age than expected in normal colonies. tially lay. This is an extreme level of cooperation Conversely, upon experimental removal of that we label as altruism. Even more impressive young bees, the youngest of the foragers is their readiness to sting any marauder of their become over-aged nurses, reverting to nursing, nest, an act that leads to their immediate death, regenerating their already atrophied hypo- as they cannot withdraw their stings from pharyngeal glands. the bodies of their victims, owing to its outward- Division of labor is also modulated by the pointing barbs. spatial distribution of tasks, and of the bees, While there are some 10 species of honey bees and by their relative sensitivities of to the cues worldwide, all belonging to the genus Apis, signaling the need to perform certain tasks. in the family Apidae, there are at least 15,000 Queens mate with several males and produce species of ants, all belonging to the family daughters of several patrilines, contributing to Formicidae, found everywhere except in the the variability in the sensitivities of the bees to Arctic and Antarctic poles. The ants have reached perform different tasks. For instance, bees differ comparable levels of social complexity. Their in their response thresholds to the smell of dead species diversity permits the ants to embrace bees so that undertaker bees are those that are many lifestyles (Hölldobler and Wilson 1990). most sensitive to the smell. If a colony is For instance, leaf-cutting ants practice a missing the most sensitive patriline, however, sophisticated form of agriculture, cultivating the intensity of the smell will soon be adequate fungi in their gardens and feeding a population for another patriline to remove the dead bees. of up to a million or more individuals only with Sources of pollen and nectar are located by the products of their labor – fungal spores. some foragers, acting as scout bees; successful Medium-sized workers go out, locate, cut, and scouts return to the hive and recruit naïve bees to transport leaves back to their nests. These pieces transport the pollen or nectar back to the hive. of leaves of carefully chosen species are then This they do by the well-known honey bee ground into a fine paste and spread in the garden dance language. When the source is nearby, they by even smaller workers. Fungal mycelia are then perform a round dance motivating the bees to “planted” in the garden, and the spores eventually search nearby for the flowers with the expected harvested. The fungi cultivated – certain kinds of smell. When the source is more than about 500 m, mushrooms – are not known to exist outside the they perform a waggle dance, communicating fungal gardens of the ants. Certain cultivars of the 4 Cooperation in Social Insects fungi appear to have been selected and passed the gamergate. Diacamma genus presents a down across generations of ant colonies and occa- unique method of reproductive regulation, leading sionally exchanged between colonies. The ants to monogamy, i.e., reproductive monopoly by one have elaborate adaptations for manuring their gar- egg-laying individual. dens with their feces and for keeping out weeds, All social wasps are paper wasps because with the help of a cocktail of antibiotics produced they construct their nests not with wax as honey by bacteria they harbor on their own bodies. bees do, not with leaves as some ants do, and In contrast, weaver ants dwell in nests on trees not with soil as termites do but with paper. built by stitching leaves together with silk threads. They manufacture their own paper by scraping While hundreds of ants use their combined effort cellulose fibers from plants, adding their own to bend and maneuver leaves in alignment, some secretions to make a pulp and drying it. All social of them squeeze well-grown larvae to persuade wasps belong to the family Vespidae. There them to donate some of their silk for the commu- is a very wide variation in the level of social nity good. Such donation of silk normally meant evolution within the Vespidae. Species belonging for their own pupation is costly to the larvae and to the subfamily Vespinae display advanced constitutes an act of altruism even before the sociality resembling the honey bees, while species individual becomes an adult. Reminiscent of the belonging to the subfamily Stenogastrinae are lazy drones in honey bees, male ant larvae socially very primitive, bordering on the solitary. are less likely to contribute silk for nest The subfamily Polistinae are intermediate and building. Weaver ants are voracious predators in are considered primitively eusocial (see below). the tropical habitats of Africa (Oecophylla Their queens and workers are not morphologi- longinoda) and Asia (Oecophylla smaragdina) cally differentiated, and most adults eclose being and build interconnected series of nests across capable of taking on both queen and worker roles. several trees, with a single queen producing all Polistine wasps have been especially useful in the eggs required to maintain their colony investigating the evolution of social behavior populations.

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