Saturday, October 3, 2015

The Ubiquitous Green Ants.

My first contact with Green Ants was when I came to North Queensland in 1958, and picked some oranges from my boss’ tree. They didn’t like my intrusion into their domain and soon had my arm full of these little biting blighters.  When I moved to Yorkeys Knob they were already inhabitants on various trees in our yard. This was a great opportunity to observe them closely, which I found extremely interesting. Following is my story about those interesting little biting creatures. - Werner
What kinds of birds build these nests?  A visitor asked me, pointing to two big leafy lumps high up in our mahogany tree. (See Photo) He was only partly right; they were nests alright, however, not made by birds, but our Green Ants, Oecophylla smaragdina.

Very few people living north of the tropic of Capricorn in Australia would not have encountered them. The Green Ant belongs to the worldwide clan of weaver ants which weave their nests together out of leaves, to create a sort of globular home. I come in contact with and, observe those insects on a daily basis as we have many trees and bushes in our yard and around us.  However, they prefer, so it seems, to build their nests on fruit trees, if there are any, thus, they are close to one of their food source such as nectar or the sweet excretions from aphids and scale insects.  Apart from that they also forage on invertebrates found on the ground or vegetation.

These unique nests are made by joining leaves together by using a silky substance produced from their larvae which they obtain from the nursery of an existing nest.
Individual colonies can become very large, with several nests spread over separate trees. They clamber all over the tree and serve to protect their nest from invaders. They are very aggressive and defend their nests vigorously, but their bites are not long lasting, nor do they have the ferocious sting of other ant species such as Bull Ants or Jumper Ants.

The colouring is obviously what distinguishes this green tree (weaver) ant from its "cousin" the red weaver found in Asia. Its body is a green or even a pale yellow, and its mandibles (Jaws) have 10+ teeth and they have 5 outer or maxillary palps segments, and 4 inner or labial palps segments. Picture: A Green Ant nest.  With time, some or all leaves die and the nest looks brown.

Worker ants transport the Larvae between their mandibles (Jaws) to the "construction site". The larva is then, with light pressure, squeezed between an ant’s mandible to produce the silk which is used to weave and stick the leaves together, which they obtain from the nursery of an existing nest. If one ant cannot reach the next leave to join it to the nest, the green tree ants will build an ant chain to slowly pull the leaves into and connect them to the nest they are building. During construction the new nest is a hive of activity, scurrying ants everywhere, as these small creatures are a great example of how team work can produce a product much bigger and complex than any individual could hope to achieve.

 The nest ends up being an oval (globular) shape up to 1/2 meter long but usually around 300mm, and because it is made from the leaves of the plant/tree it is constructed in; it is often well camouflaged and hard to see. One colony can have any number of "individual" nests on one and nearby trees, making up their colony. Picture: Nest under construction.

Over the years I have experienced many times the aggressiveness of these ants when I have to pick fruit from our Soursop tree and in particular our big mango tree.  If you accidentally knock their nest then it doesn’t take long before you are covered with countless ants biting you.  While you can tolerate their bites for a while, but lots ants attacking simultaneously can be rather uncomfortable. You don’t even have to knock their nest, just getting too close to it and they are at you.

However once they get inside your clothes, especially the underpants, then a tactical retreat to the ground is the best option. Taking your clothes off and shaking them out to get rid of some, but to get them out of your body hair, usually requires the assistance of my wife, as it is not easy to get them off the back by yourself. This procedure takes place as often as I climb into the tree to pick fruit – these confounded ants don’t seem to understand that it is my tree and not theirs.

The trees they have in mango plantations today are especially bred to grow a much smaller trees size and the fruit can be picked with mechanical devises and the Green Ants are not much of a bother, if any. When I planted our tree in 1971 it was in a little pot. In those days you couldn’t get the smaller tree variety. As I write this story (2004) this tree is 10 meters high the tree trunk has a girth of 1.5 meters and a diameter of 80 centimeters.

It has also been found that Green Ants are valuable asset to mango and citrus growers as they keep aphids and scale insects at bay in their plantations, apart from that they also help with pollination. Oil from their abdomen has also been used by indigenous aboriginal people for sweetening water and for medical purposes.

 I find it interesting to observe them walking along the cross rails of my fence; it is a busy “Ant Highway” and it is a two-way traffic. When two ants, going in different directions meet, they stop for a moment, then are on the way again.  I assume, they say hello, sniff each other out or tell where to find food, it would really be interesting to know.  I have seen Green Ants carrying little pieces of white fragments, probably an aphid, and another ant wants to take it, then the ant either turns around or goes around the other ant and escapes.  So, it looks that they have also thieves amongst them.

Sometimes, I observe a number of Green Ants standing in a circle with their heads in the centre and nearly touching each other, or a whole bunch of ants congregating on the fence post, it looks like that they’re having a meeting. You can find Green Ants just about everywhere wandering around here in the north and far away from their nests. No doubt, they must have a build-in guidance system to find their way back to their nest. I often wonder who gives the command to do whatever they do, or is it pure instinct and all their tasks are programmed and embedded into their little brains or whatever it is they think with.
Every time I open our second gate to our property I interrupt their march along the fence and by the time I close the gate there is a big assembly of green ants at both ends of the opening, waiting for their highway to be “reopened.” While these little creatures are very ingenious in many ways, they seem to be unable to think of going down the open gate to the ground and up again on the other side and join their mates on the other side.

Appendix.The Green Ants and the dead lizard.

Some time ago I had a rare opportunity, to watch a natural spectacle to unfold in front of me.  As I walked out to my backyard I saw a great number of Green Ants, they are about 6 to 8 mm long; pushing a lizard 150 mm long up my sunshade post.  The picture I took of it was described by friends as one in a million. It took 30 minutes to move 30 cm up the post. I’m still puzzled by their action and wondering why they were doing this as they could not be called carnivores and, as I wrote before, they live mainly from the sweet substance exuded by aphids, but also devour small invertebrates.  This happened just before our Wet Season, and the instinct must have told them to bring it to a higher ground.

However, the moral of this story is: With teamwork anything can be achieved. It just shows that the difference between success and failure is a great team. And, Helen Keller was so right when she said: "Alone we can do so little, together we can do so much."
See also: Our Skyrail at Smithfield and Green Ants.
My thought for today.
– Werner
If everyone is moving forward together, then success takes care of itself. -- Henry Ford


Heidi, Germany said...

I just read this interesting ant story! So typical of you Werner! Informative and personal! I like the picture of the lizard! Thanks for that!

Jill Wilmot said...

Thank you, Werner for this interesting read. I’ll certainly look now at my Green Ants in my yard in a different light. I totally agree with Heidi’s comment about you.

Donna Waldman said...

Yes green ants can be very agressive. I have had to run from the garden into the shower in a hurry to get rid of them. However they are obviously an important part of the eco system and we really do need them. Thankyou for this interesting story Werner, and I look forward to the next one.