Read the first of this two-part series on the common ants of Karnataka, here: Common Ants of Karnataka: Part 1
On a hot afternoon, when all appears silent on a small grassland patch, a small army is at work harvesting grass seeds and taking them back to their nest where they are de-husked and crushed into powder to be consumed. These are the industrious harvester ants of our grasslands. Harvester ants are polymorphic, meaning that a single colony will have workers of different sizes and shapes. Workers of each size have different roles to play, ranging from nursing duties to colony defence. The largest workers defend the colony against intruders and also crush seeds like a sledgehammer, while the smallest workers sit on the heads of the largest workers and help ward off phorid flies which try to parasitise the larger workers by laying eggs on their head. Mid-sized workers perform a multitude of tasks ranging from scouting the grassland for suitable foraging sites to taking care of the larvae.
East Indian Harvester Ant (Carebara diversa)
A very common species of harvester ants distributed across peninsular India, along with ants from the genus Pheidole and Monomorium, these ants are responsible for consuming tons of grass seeds and herbage every year. In spite of this, they are poor dispersers of seeds and only a few seeds that accidentally fall off while in transportation actually germinate. They also occasionally hunt termites. Their nests are underground, with multiple nest openings; each opening has seed husk strewn around it.
The Tree Women
While most ants evolved to live a subterranean life, some went in the opposite direction, specialising to live on trees. From a simple hole excavated in a branch to intricate paper nests, ants of this class have out-competed their competitors to exploit a private niche that they defend fiercely. Being active hunters, tenders of aphid and hopper herds, and exploiters of plant nectar, these ants exploit all sources of food available to them. Special defence mechanisms developed over evolutionary time help them against predators like arboreal geckos and birds; these mechanisms include a complicated array of spikes and shields, to razor-sharp teeth and loads of formic acid.
Asian Weaver Ant (Oecophylla smaragdina)
The undoubted insect ruler of the tree canopy, the Asian Weaver Ant outsmarts and out-competes every other insect that lives on trees. From fierce predators to artistic weavers and engineers, this species is so successful that no other species of ants invades their territory, and if there is a chance confrontation, it is war, as dramatic as many of our war movies! They have very sharp, needle-tipped teeth, which they use to clasp their prey. Its flexible abdomen can swivel by 180 degrees and administer a potent dose of formic acid in the wound it creates using its mandibles. They hunt live prey in loose packs and kill them by stretching the appendages of the prey to the maximum and tearing them apart. They make beautifully woven leaf-nests which are held in place by the silk produced by their larvae; the process of the construction of their nest is a story in itself. Interestingly, unlike the workers, the queen of the Asian Weaver Ant is green in colour.
Acrobat Ant (Crematogaster sp.)
This is a general name given to all species of the genus Crematogaster. They are one of the very few ant groups that have a worldwide distribution. They are commonly also called the ‘Valentine Ant’ because of their heart-shaped abdomen, or the ‘Cocktail Ant’ because of their behaviour to raise their abdomen when alarmed. The nesting habit of this group is diverse; while some live in excavated chambers in dead trees, others make elaborate carton nests which are made using mashed wood and saliva. They are generalists, and apart from actively hunting other insects, will also scavenge, and tend to aphids and hoppers.
Bi-coloured Arboreal Ant (Tetraponera rufonigra)
This is a very common ant which most of us would have especially encountered on Mango trees, and will remember them for having given us our most painful ant sting. They have a very long and slender body with well-developed and conspicuously placed eyes. Their sting packs a very potent dose of venom and can cause mild to severe allergic reactions in humans. They nest in the dry portions of a tree, by usually excavating a small chamber.
These ants belong to the primitive subfamily of Ponerinae. They are active hunters and have a well-developed sting, which they use to hunt and subdue their prey. They also use their well-developed eyes to locate their prey. While some of these ants are generalist predators hunting anything from termites to other ants, others are specialists and will only hunt a special type of prey. Hunting strategies differ widely; while some hunt in packs, others hunt in pairs, and on rare occasions, solitarily.
Procession Ant (Leptogenys processionalis)
One of the most efficient hunters in the ant world, these ants’ foraging habits are similar to that of the African Army Ants. They move in three-to-five-column-wide trails and will devour anything that comes in their path. When the Procession Ant colony moves, the column produces a low humming noise due to the movement of legs and antennae; this sound is amplified when the column is disturbed. They have razor-sharp mandibles and a very potent sting.
Sri Lanka ‘Queenless’ Ant (Diacamma ceylonense)
This is a species from a very unique group where there is no distinct queen ant. Worker ants of this species engage in a constant fight of domination, and when an old reproductive female weakens, the strongest worker kills the reigning female and takes control of the nest. They are predatory and usually hunt termite larvae and beetle grubs. They have a well-developed sting and hunt in pairs.
Jerdon’s Jumping Ant (Harpegnathos saltator)
The Tigress of the ant world, the Jerdon’s Jumping Ant is one of the most accomplished hunters. Well-developed eyes, tusk-like jaws, and a very potent sting make this ant a hunting machine – one of the few ants that hunts solitarily, usually by ambushing its prey. They have phenomenal jumping abilities which they use to surprise their prey. Once the ant has its prey in sight, it stalks it until it is confident of ambushing it successfully. The ant then jumps from a vantage point with its jaws wide open, and takes down the oblivious prey in a matter of seconds. The Jerdon’s Jumping Ant is quite common in the wooded regions of Bengaluru city, and is one of the top ant predators of the Western Ghats’ forest floor.