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Agriculture is almost unknown in the natural world. Human beings are the only vertebrates known to grow crops or keep livestock (with the possible exception of damselfish which carefully tend little algae gardens).  And yet we were not the first animals to invent the concept.  Ants have farmed fungi within their tunnels for tens of millions of years.  Ants also keep aphids in captivity in order to “milk” them of sugary secretions–or to eat them outright.  It is possible that beetles, termite, or snails came up with the concept first, but most evidence points to ants as the first farmers.

An Ant Milking Aphids

Ants do not have a shabby operation either. Leaf cutter ants form the largest and most complicated animal societies known on Earth (other than our own) and a single colony can have over 8 million individuals.  Leaf cutters are an ideal example of how adept ants are at farming fungi.  Four different castes of worker ants work together to bring back leaf fragments and integrate them into huge fungal gardens. Different species of leafcutters cultivate different fungi from the Lepiotaceae family.  Certain bacteria with antifungicidal and antibacterial properties grow within the metapleural glands of the ants.  The worker ants use these bacteria to “prune and weed” dangerous or unproductive organisms out of their gardens.  Older (more expendable) worker ants carry waste products from the hive to a waste pile where they stir the hive wastes together to aid in decomposition.  The waste-management job brings the danger of fungal or bacterial contamination and contaminated ants are exiled to certain death in order to keep the gardens safe.  Additionally dead ants from within the hive are carefully placed around the waste pile so as to protect the hive from their decomposition.

Leaf Cutter Ants at the Cameron Currie Lab arrange cut-up leaves into their fungal garden.

According to geneticists who study the rates of mutation within the various fungal cultivars, ants began their farm relationship with fungi around 50 million years ago in the warm Eocene epoch (an era which saw many of the critical relationships in modern ecosystems begin).

 

Digital Cut-away of an underground leaf-cutter nest

Scientists are also beginning to understand the means by which ants herd their little flocks of aphids.  The aphids are smaller insects which feed on the saps and juices of plants (which they suck out by means of specialized mouthparts called stylets).  The ants prevent the aphids by flying away by tearing off their wings.  The feet of the ants produce chemicals which tranquilize and subdue the aphids and keep them from escaping the “pastures” near the ant colonies.  It is believed that aphids also derive certain benefits from this arrangement since the aggressive ants protect them from many of their natural predators.

An Ant with a “herd” of Aphids

For years naysayers belittled the farming achievements of ants suggesting they were little more than symbiotic arrangements.  However as entomologists study the ants more carefully they increasingly discover just how complicated and sophisticated those relationships are (involving as they do numerous symbiotic relationships with bacteria in order to produce the chemicals necessary for agricultural control).  Additionally, what are humankind’s relationships with our crops and animals if not huge harrowing examples of symbiosis?

Chullachaqui (painting by David Hewson)

If you are wondering through the great untouched rainforests of the Amazon basin, you will sometimes come across a clearing devoid of all vegetation save for a few trees.  These bare patches are known as devil’s gardens and are said to be the haunt of the fearsome Chuyachaqui (or Chullachaqui), a shape shifting demon which delights in causing misfortune to travelers.  Although the Chuyachaqui’s default form is that of a small misshapen man with one hoof and one human foot, the demon can change shape into a person known to the traveler in order to mislead the latter to doom.

Lemon ants (Myrmelachista schumanni), so named because they are said to have an acidic lemony taste

Scientists were curious about these small bare patches of forest. After carefully studying the ecosystem, they discovered that a force nearly as diabolical as the Chuyachaqui is responsible.  The lemon ant, Myrmelachista schumanni, produces formic acid, a natural herbicide which it methodically injects into the plants in a “devil’s clearing”.  The only plants which the ants leaves alone are Duroia hirsuta, “lemon ant trees” which have evolved a mutualistic relationship with the ants.  The lemon ants keep the forest free of competing trees and plants, while the lemon ant tree is hollow inside—a perfect natural ant hive and its leaves provide a source of nutrition for the lemon ants (which are a sort of leaf-cutter).

A clearing filled with lemon ant trees

Large colonies of lemon ant trees have been found which are believed to be more than 800 years old—far older than the life of any ant colony or individual tree.  It is remarkable to think these ant/tree settlements have been part of the rainforest since before the Mongol conquests.

Driver Ants

One of the strangest and most alarming creatures on the planet is the driver ant.  Driver ants belong to the genus Dorylus which is comprised of about 60 species.  In the larger Dorylus species, each worker ant is only half a centimeter long.  The soldier ants which guard the hive are a mere 1.5 centimeters.  Males, which can fly, are 3 centimeters long and the queen, the largest of the ants, is from 5 to 8 centimeters long.  These are not the sort of sizes that allow one to play professional football, so what makes Dorsylus ants so fearsome?  Well, there are lots of them.  Driver ants form the largest colonies of all the social insects.  They live in hives numbering more than 20 million individuals, all born by one single queen.

When marching or foraging, these hives can overrun and overpower much larger animals and generally everything that can do so gets out of their way (including mighty elephants).

Driver ant head: close-up (Dorylus nigricans)

Driver ants are usually found in the tropical forests of West Africa (although some species range into tropical Asia). Although capable of stinging, the ants rarely do so.  They prefer to use their powerful sharpened mandibles to shear apart prey.  Not only are these mandibles powerful the pliers-like pincers lock into a death grip if the ant itself is killed (or even beheaded).

Male Driver Ant ("Sausage Fly")

Male driver ants fly away from the colony very soon after birth.  If a colony of foraging driver ants comes across a male ant they rip off his wings and take him to mate with a virgin queen (after which he dies).  The queen ant then lays 1 to 2 million eggs per month for the remainder of her life.

All driver ants are blind, but they have an acute sense of touch and smell.  Larger columns follow scent trails laid down by scouts.  The ants eat any animal life they can get their mandibles on (although the staple of their diet is apparently worms).

Close-up of the enormous queen of an army ant (Dorylus anomma nigricans) colony being protected and tended to by worker and soldier ants during migration of the colony.

When driver ants have stripped the animal life from a particular section of the forest they nomadically pull up stakes and move on en masse.  Developing larvae are carried in temporary nests made up of the living bodies of worker ants.  Foraging columns or hives on the move are dangerous.  While healthy animals can escape, injured or trapped animals can be killed by the ants which enter the mouths and nostrils of victims.  One shudders to think of the bad ends which have befallen people who were wounded, bound, or seriously drunk when driver ants were passing through.  Farmers however have a different relationship with the ants which can clear entire fields of all agricultural pests in an afternoon.

An Iridescent Wasp on a Linen Tablecloth

Today I would like to start a brand new animal category concerning the most gifted of the social insects, the superorder Hymenoptera, which consists of wasps, bees, ants and sawflies (along with some other oddballs which are less frequently mentioned).  Hymenoptera are arguably among the most successful creatures on the planet.  Their behavior can be almost embarrassingly humanlike and they are famous for building elaborate constructions, going to war, taking slaves, farming fungi, and crafting rigid city-like social hierarchies. However, of all life forms on earth, the hymenoptera are some of the most vividly alien: cuttlefish do seem downright cuddly when compared to the horrifying digger wasps.   A sociologist could happily draw parallels between a bee hive and a city until he looked at the details of bee reproduction, at which point he would probably break down and weep.

The Hymenoptera are not as ancient as either the mollusks or the mammals (if it is fair to compare an order with a phylum or a class).  They originated in the Triassic and did not develop the successful social organization which is now such a defining feature until the late Cretaceous.   The first hymenopterans were the xylidae, a family of sawflies with a minimal presence on earth today but with a long pedigree. These first sawflies fed on the pollen and buds of the conifer stands beneath which the first dinosaurs developed (and under the roots of which the first mammals cowered).  The rise of the flowering plants in the Cretaceous led to a leap-forward for these pollen-eaters: complex flowers then evolved in tandem with the hymenopterans. It was also during the Cretaceous that the ants and termites split from the vespoid wasps.  The earliest honey bees of the familiar genus Apis evolved at the end of the Eocene bt they were preceded by all sorts of hymenopteran pollinators.

A Sawfly Fossil (Hymenoptera: Symphyta)

I mentioned above that, for all of their familiarity to us, the Hymenoptera are disturbingly alien.  In fact as I have been writing this comparatively tame post, a dreadful sense of formication has stolen over me and I find myself brushing phantom ants from my limbs and feeling the terrible pang of yellowjacket stings from childhood.  The hymenoptera are frequently the basis of the extraterrestrial enemies in science fiction.  Although people are occasionally stung to death by wasps or ripped apart from within by driver ants, it is something larger and less tangible which makes the hymenoptera such reliable villains. I have watched the soldier bees snip the wings off of wasps trying to invade my grandfather’s bee hive and then toss the invaders’ writhing bodies from the painted ledge—all while a river of worker bees went out and came back laden with pollen.  There is an alarming touch of civilization to these social insects: a hint that they are utilizing the same kinds of organization and communication which have made humans such a success.  And, in fact, the social insects are a huge success—ants alone are estimated to constitute a substantial portion of the animal biomass of earth (to say nothing of termites, bees, wasps and the rest).

Yellow Jackets on a Coke Can (photo by the fearless Alan Cressler)

Of course this success has broad ramifications. The hymenoptera are everywhere in nature and they also play a huge part of human culture. Indeed the very name of this blog is a play on words between my surname and the noble art of aviculture.  Without the bees, we would not have much in the way of fruit or vegetables.  Not only would this be a disaster for human farming—just contemplate how many other creatures rely on those fruit!  Similarly the ants bulwark an entire portion of the ecosystem by scavenging the tidbits out of fields and forests.  Writing about the hymenoptera may be an itchy, antsy business but it is a well-merited study.  This group of insects is pivotal to life on dry-land as we know it.  The biblical promised land was one of milk and honey.  There would be no milk without mammals, but there would be no honey (and precious few mammals) without the hymenoptera.

A beekeeper completely covered with swarming honey bees in a “bee man” cantest in China

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