Leafcuter Ants

  
Leafcutter Ants

Leafcutter ants are one of Earth’s amazing creatures. Next to humans, leafcutter ants are
the most socially complex organism on our planet. Leafcutter ants are found in the
rainforests of the Neotropics, from the southern USA to South America. Despite their
small size, they have a huge impact on their rainforest environment. Leafcutter ants
are ecological engineers, shaping the rainforest environment in significant ways,
and adding hundreds of thousands of kilograms of leaf litter to the soil every year.
This makes them one of the most important keystone species.
 


1. Leafcutter ants are hard-working farmers  

You may be wondering why leafcutter ants collect leaves incessantly day and night?
They actually don’t eat the leaves. Instead, the leaves are crucial to cultivating 
their fungus garden. Leafcutter ants cut leaves with their strong jaws and bring them
back to their underground nests where they are then chewed up to form a nutritional
substrate on which a fungus grows. Leafcutter ants are fungus-farming ants, and they
have a mutualistic relationship with the fungus. In order to keep their fungus gardens
healthy and producing the fungus they need to feed the colony; workers forage constantly
to bring fresh leaves back to their nest.  

Leafcutter ants are selective in which species of plants they collect leaves from.
A study conducted in Costa Rica showed that they have a preference for woody species
(rather than herbaceous plants) and introduced species rather than native plants. Plant
preferences can change from season to season, and some plants are avoided altogether.
Plants contain different compounds, some even fungicidal, that would be toxic to the
fungus the leafcutters cultivate, thus not a good choice to bring back to the nest.
Interestingly, watching leafcutter ants select some plants over others has led to the
 discovery of antifungal chemicals and medicinal plants.

2. A leafcutter ant can carry 10-50 times its own weight

Leafcutter ants are incredibly strong. Their body distribution and joint strength allow 
them to carry a weight much greater than they are. On top of that, they have formidable 
jaws, and they carry leaves, twigs, and flowers over their head. If a human could lift 50
 times our body weight, we would be able to lift a hippopotamus over our head—with only
 our jaws! Imagine lifting 2 cars over your head—wow!

3. Some leafcutter ants have armor in the exoskeleton

We know that leafcutter ants are strong – they have super strong jaws and are the
weightlifting champions of the insect world. But in a recent publication, a new discovery
gives us even more insight into leafcutter ants. One species of leafcutter ant, Acromyrmex
echinatior, was recently found to have a special biomineral, similar to dolomite,
embedded in its already tough exoskeleton. Made from calcite with high levels of magnesium,
it forms a very strong armor all over its body. Until now, this biomineral has never been 
found in any other insect; it is known from only one other living creature – found in the
 powerful teeth of sea urchins.

Experiments show that ants with this biomineral acting as armor loses fewer limbs during
battles with other ants than other ants without it. Also, it does a good job of fending
off fungal infections. While it has only been identified in one species of leafcutter
ant so far, there is a good chance that other species have this biomineral in their 
exoskeleton as well.

4. An adult human would be able to stand inside a leafcutter ant nest

Leafcutter ant nests comprise thousands of chambers of different sizes, which are connected 
by tunnels. They nest underground, so keep this in mind when you walk through the
 rainforest. You might unknowingly have a huge super city under your feet! The central 
 chamber of a leafcutter ant nest is the largest fungus garden chamber, and in a large
  colony, it is big enough for an adult human to stand inside!


5. Leafcutter ants travel up to 30 meters to collect leaves  

These ants work tirelessly day and night, traveling big distances from the nest to forage
for leaves. They not only stay on or close the ground, but they will also even climb tree
trunks into the rainforest canopy (trees up to 30 meters tall!) to reach valuable leaves.
They often create and follow cleared “highways,” some up to several inches wide, to
efficiently reach their foraging areas. While they may appear to defoliate an entire
plant, cutting the leaves actually helps to stimulate leaf growth, just like pruning 
your garden plants! This way, the leafcutter ants ensure they will always have leaves
to forage in all directions around their nest. So, they are not harming the plants,
they are actually helping them grow! Just another one of the amazing leafcutter ant
facts out there!

6. (Most) leafcutter ants are females 

A leafcutter ant colony can contain up to 10 million individuals, consisting of a single
 queen, larvae, workers, and soldiers. Next to humans, leafcutter ants are the most 
 socially complex society on Earth! Leafcutter ants are polymorphic, which means 
 individuals of the same species come in different sizes and forms. The queen ant
 is the largest ant in the colony, reaching 22 mm in length. She can lay up to 30,000
 eggs per day!
                                                                               
During the non-reproductive months, all leafcutter ants (other than the queen) in the
colony are infertile females. Worker leafcutter ants come in different sizes, depending
on the role they have in the colony. Scientists categorize them into 4 general
sizes: minims, minors, media, and majors. Did you know that there are workers that
forage to collect leaves, tend the fungus gardens, brood larvae, remove parasites 
from leaves, take out the trash, and patrol and defend the terrain? Depending on 
their role, they range in size from a head width of 1 mm to 7 mm, with the largest
soldiers reaching 16 mm in length! Furthermore, the workers take initiative and
decide the division of labor within the colony, rather than the queen delegating tasks.

But, what about the males? When it comes time to reproduce, reproductive individuals
called alates—winged females and males—leave the colony and engage in nuptial flights.
Each female takes a small amount of the fungus with her when she flies from the colony,
and mates with multiple males to collect a large amount of sperm. After mating, the
male dies. The female will settle to the ground, lose her wings, and search for a
suitable place to start her colony as a new queen. It’s not easy though, and only 
2.5% of new queens survive to start a new colony.

7. There are over 40 species of leafcutter ants

There are currently 47 recognized species of leaf-cutting ants. They are classified
into the genera Atta and Acromyrmex and they are endemic to the Neotropics. All
leafcutter ants are fungus-farming ants. Although not all fungus-farming ants are
leafcutter ants—there are approximately 250 species of fungus-farming ants found 
on Earth.

8. Leafcutter ants protect their fungus with antibiotic-producing bacteria

Finally one of the most fascinating leafcutter ant facts is that they protect their
fungus from potentially dangerous microbes. To keep the fungus gardens healthy, a key
player in the leafcutter ant colony is important bacteria. The bacteria is carried on
the ants’ bodies and it keeps microbes from damaging the fungus. Scientists are
studying leafcutter ant communities, especially in relation to the bacteria, as it
can be applied to making pharmaceutical drugs for humans, especially antibiotics. So
we can think of leafcutter ants not only as farmers but also as pharmacists!