Team: : Satpal Singh with Devanshu Gupta, Ajay Bajpai and VikramTiwari
Images : Satpal Singh Text: Devanshu Gupta

Forget the butterflies, for when it comes to social networking, the ubiquitous ant leaves the rest far behind. On this assignment, we probe into the deeply complex and fascinating lives of weaver ants as observed on the Indo-Gangetic plain, whose sheer range of engineering, organising and communication skills has left our expedition team spell-bound

WEAVING IN UNISON | During the nest-building process, a number of leaves are stretched into position for binding, and each leaf is held in place by rows of workers, as depicted in the picture. As soon as all the leaves are brought together, the process of stitching them starts. This amazing behaviour gives them the name, ‘weaver’ ants.

Since childhood, we have noticed lines of ants making trails inside our houses, and denounced them as irritating pests meant for eradication; without considering their significance in our ecosystem. These tiny creatures appeared on this planet about 145 million years ago, long before the age of apes and arrival of the human race; they even witnessed the extinction of dinosaurs. As taxonomic explorations continue, scientists expect the diversity to rise from the current 12,500 species to about 22,000 species, and out of these, 660 have been found in our country till now, occupying almost all terrestrial habitats, including deserts and high mountains. Besides being pollinators, scavengers and soil turners, they also biologically control several types of pests, indicate the ecological health of the environment, and are significant components in the food chain. Like other social insects, ants follow a highly sophisticated division of labour, with different members of the colony performing specific functions.
With SAEVUS giving us an opportunity to work on these fascinating insects, we proceeded to peep into the eventful lives of weaver ants, carefully spying through our lenses rather than directly entering their kingdom.

Origin of the species
As humans, we often take pride in our unique civilisation and culture, but tend to overlook the stories found in a thriving kingdom of weaver ants, which can appear to be full of life while constantly battling perils brought about by different predators. These ants are predominant members of forest insect communities, and found throughout the entire tropical world, except America. They belong to the genus: Oecophylla, a relatively old genus in the family: Formicidae (sub-familyFormicinae), of the insect order Hymenoptera. There are 11 fossil species reported from the Oligocene and Miocene periods, along with two extant species: Oecophylla longinoda, occurring widely across Afrotropical regions, and Oecophylla smaragdina, found in the Oriental, Palaearctic and Australian regions. Interestingly, the Oecophylla smaragdina was discovered between 3.6 and 7.8 million years ago, somewhere in China. Since then, the Chinese have been using these ants for pest control purposes; they are commonly known as Yellow citrus ants, and can be spotted on mango, citrus and guava trees in our country.

HAPPY TO HELP | Whenever a forager locates a dying insect, it not only informs the others through speciesspecific pheromones, but also through a tactile communication system. In this picture, two workers are touching their mandibles to pass information. The message is carried forward similarly among other colony members, alerting them to food or danger.

This year, the entire Gangetic plain of Uttar Pradesh witnessed a very good crop of mango, and large hordes of these weaver ants were not to be left behind. At first glance, the regular movements of these insects carrying food from one place to another in a chain, got us curious about their ethological activities. To dig deeper, we visited various locations in and around the buffer zone of Dudhwa Tiger Reserve in south and north Kheri, Malihabad region near Lucknow, Bareilly, Shahjahanpur, Pooranpur, and various agro-ecosystems of Lakhimpur district, to get some candid shots from their lives. We observed the composition of their nests and their daily activities on mango plantations, and other trees including Jamun (Syzygium cumini), Bargad (Ficus benghalensis), Mahua (Madhuca indica), Peepal (Ficus religiosa), Nashpati (Pyrus pyrifolia), Sal (Shorea robusta), Arjun (Terminalia arjuna), and Behera (Terminalia bellirica), from dawn to dusk for about 15 days. Observations were made on their colony structure, nest formation, care of young ones, feeding habit, potential preypredator relationships and associations with their own enemies.

SWEET HOME | The density and composition of workers usually decides the size of the ant nest, which may vary from a single folded leaf to many hundreds. Interestingly, a single colony not only makes one large nest but also additional 'barrack nests' to look after their injured companions, young ones and eggs.

Family life
Like other social insects, the colony of weaver ants is polymorphic, consisting of a queen, winged males, and infertile wingless workers. The virgin sexual members, which includes future queens and males, possess wings; but a gravid queen will shed her wings after mating and prefer a sedentary lifestyle, conserving her energy exclusively for egg development. A mature colony is strictly monogynous: it can only accommodate one reproductively active queen. There is a clear division of labour among worker ants, who are differentiated into soldiers, foragers and feeders. Minor workers stay inside the nest to care for the juveniles in the queen's brood, while the major ones perform outdoor tasks of foraging and defence.

QUEEN SUPREME | In the picture, the wings of the queen are indication of her virginity, before she mates with an eligible male. After insemination, she lays eggs within few days of shedding her wings.

A colony begins when a queen, after mating, finds a sheltered site for a first nest between the leaves of a tree or shrub. The queen mates with a successful, strong male during nuptial flights in the air, usually after the monsoon showers.
Soon after mating, the male ant dies. The gravid queen then dealates herself (sheds her wings) and searches for a a good place to lay her first brood of eggs. Soon, eggs hatch into rice-shaped, white and delicate larvae, which then transform into pupae, before finally metamorphosing as workers. From this point on, the entire responsibility of the family, the queen and her juveniles rest on the shoulders of these industrious and highly active worker ants.

TEAM EFFORT | In this image, one ant is helping another turn the leaf in a suitable position so as to fit the requirement. The ants make their nests with the leaves of the tree sewn together, and they exhibit unbinding cooperation in making this difficult task a reality.

Engineers at work
Weaver ants demonstrate tremendous architectural skills that aid them in building nests with leaves. When a new nest is required, individual workers scout for suitable clusters of leaves, grabbing these with their mandibles and drawing them together. Meanwhile, other workers gather to the site, presumably influenced by the success of the first, and join the effort. To join the two leaves, the ants form chains by holding each other's waists and pulling the leaves together.

BRIDGEMAKERS | When major workers can't cross a gap in the terrain by walking, they attempt to traverse it through a bridge built by stretching their odies. This behaviour was chiefly observed when they were transporting large prey. such as bugs and other ant species, from one twig to another.

Subsequently, a number of leaves are stretched into position for binding, each held in place by rows of workers. As soon as all the leaves are brought together, the process of stitching these leaves commences: the mature and experienced workers capture the transparent lateinstar larvae in their mandibles and delicately move them to and fro on the edges of the leaves. In response to this movement, the larvae release sticky material from their glands, and a white sheet of silk joins the leaves one by one. This behavioural characteristic of ‘weaving' leaves for nest formation is unique among these ants, as also the reason behind their name. In reality, they are essentially sticking the leaves together.
The weaving of the nest may extend late into the night. The size of the nest also varies from a single folded leaf to several hundreds. During the course of our observations, we noticed an interesting fact: a single colony builds not only one large nest but also additional ‘barrack nests' to look after their injured companions, young ones and eggs.

BOUNTY HUNTERS | In this picture, two worker ants are coming out of their nest to forage for food.

Passing the message
For ensuring the survival of the colony, the workers foster unbound cooperation and high degrees of unselfishness. They exhibit a variety of striking and magnificent behaviour such as collaboration with nest mates, defending the nest from robbers, organising food raids, and caring for adolescent ants in the nest.
To execute all these tasks and maintain their territory, they use a complex and highly-developed chemical communication system, in combination with keen vision and tactile cues. They rely on chemical messengers called ‘pheromones' to elicit a specific response from fellow workers. When a forager locates a large
dying insect, they use not only species-specific pheromones but also a tactile communication system to contact other members.
We observed that the pheromones may be used passively in the form of trail markers, or actively, by being passed onto other members through tactile means, such as when an ant touches another with their mandible to transfer information. The same action is followed by other members to make the colony aware of the location of food. In similar fashion, several workers act as a team when they need to subdue prey or carry it back to their nest.

DEATH TRAP | Sometimes, the ants get trapped in the gum secreted by plants during nest activities. Though their legs get completely stuck, they nevertheless struggle to free themselves. Fellow workers are unable to help and usually just stand aside helplessly watching them try until their last breath.

Prepared for all odds
These ants act are important consitituents of the forest canopy, exerting a controlling influence on other arboreal insect fauna through predation and competition for food resources. The weaver ants also control pests by introducing them onto mango trees where they have nests, thus naturally acting as a biological pest control.
Predation of other insect fauna by this ant is also extremely impressive. As per our observation, it appears that they are born to kill whoever comes in their path. We monitored that they predate mighty beetles, beautiful caterpillars of moths and butterflies, delicate bugs, annoying flies, economically important honey bees, carpenter bees, large wasps, mantids and their egg cases, spiders and even agriculturally significant ladybird beetles. The main preys found during our study were mango stone weevils (Sternochetus mangiferae), mango fruit flies (Bactrocera dorsalis), seven-spotted ladybird beetle (Coccinella septumpunctata), wasp moth (Syntomis georgina), honey bees (Apis sp.), and red hemipteran bug (Spilostethus militaris). These master architects and engineers are also capable of building bridges to acquire food resources. Interestingly, this ability of simple-minded ants to co-ordinate such complex assignments has been studied for applications in robotics, with a view to build simple, cheap robots that could carry out intricate tasks.
Whenever major workers cannot cross a gap in the terrain by walking, they attempt to traverse it by building bridges with their bodies. After crowding at the edge, the workers stretch their bodies toward the other end of the gap, often holding this posture rigidly for minutes on end. Other workers then climb
over the bodies of their nest mates, and a living bridge begins to take shape (see image on Pg 17). When a bridge is constructed and some of the ants are able to cross over, the successful explorers return back to the nest with the help of odour trails released from their rectal glands. Such chemical recruitment
only occurs after workers have crossed the bridge and examined the object on the other side. Odour trails are then laid all over the surface of the object and even over the bodies of the nest mates forming the living bridge. We observed this behaviour of constructing bridges being used when the ants were
transporting large preys such as bugs from one twig to another.

FRIENDS FOR LIFE | Cooperation is at its peak in this picture. Whenever any ant gets injured in activities or territorial fights, the healthy ones will help it to reach the nest. They hold it delicately by their petiole region or near the neck during the transfer process.

Friends and foes
The co-evolution of weaver ants with that of aphids, scale insects and mealybugs have resulted in strong symbiotic associations, where these ants obtain food in the form of honeydew from the mealybugs. In return, they not only protect these sap-feeding insects from enemies like the Seven-spotted ladybird beetle, but
also shift them from old to young shoots of the plant. Though we did not observe any ant quenching its thirst on honeydew, we did notice them waiting to obtain it from the mealybugs. Primarily, mango mealybugs (Drosicha mangiferae) were observed during the study period for their association with the weaver ants.
The ants also have a very close relationship with predatory spiders, who are both a visual and a chemical mimic of the ant. This ant-mimic spider (family: Salticidae) feeds on ant larvae and lives quite comfortably inside ant nests, although it tends to avoid direct contact with major workers. Spiders are likely
to be able to move between colonies, though they appear to have more success acquiring larvae from minor workers in their host colony than from workers in other colonies. The difference seems to occur as a result of change in the behaviour of the spider rather than of the ants. Weaver ants are also host to
Myrmarachne spiders, who have derived a large measure of independence in their pattern of speciation from the wide range of host ants they mimic. The larvae of some Lycaenid butterflies also feed exclusively on the larvae of the weaver ant.

ENERGY DRINK | The ants maintain a symbiotic relationship with insects such as mango mealybugs. These bugs provide the ants with honeydew, an important glucose supplement in their diet, and in turn, the ants protect them from other predators.

In conclusion
What's fascinating is that the weaver ant is not just ecologically important, but also of considerable economic value as a biological control agent in food and medicine, and also as a potential pest itself. This humble ant was recognised in China as a ‘Biological Control Agent' as early as 304 A.D. Their predatory capacity makes them an effective tool in controlling pests in several tropical orchards. The weaver ants, combined with soft chemical applications, reduce the numbers and effects of many infiltrators, including the mango stone weevil, fruit fly and red hemipteran bug in mango plantations. Compared to the treatment done by chemical insecticides, the employment of weaver ants for pest control in orchards is far safer and environment friendly, resulting in significantly reduced levels of rejected fruits.

“Interestingly, the ability of simple-minded ants to co-ordinate such complex assignments has been studied for applications in robotics, with a view to build simple, cheap robots that could carry out intricate tasks.”

A 22-year-old award-winning wildlife and nature photographer, Satpal Singh is based in Lakhimpur Uttar Pradesh with an M.Sc in Zoology. He has a keen interest in covering and highlighting the beauty of the smaller and often overlooked members of our ecosystem. Satpal has over 21 photography awards across national and international contests, and his work has been featured in several publications worldwide. At present, he is working on studies related to the insects of North India.


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