Sunday, 19 October 2014

A story of Stings and Bites

I am aware that a lot of you have been attacked by ants on various occasions, so let me ask you a simple question- did the ant sting you or did it bite you?


I too was when I was attacked many years ago by a Procession Ant | Leptogenys processionalis (Jerdon, 1851) (Fig. 1) and it took me some years to realize that I was "stung", but does it mean that I was not bitten? Turns out that I was bitten too!!!

Fig. 1: Procession Ant | Leptogenys processionalis

So, what do ants do? Sting, bite or both? Do all ants sting? Is the ant sting venomous? Can a human die if stung by an ant? Which ant's sting/ bite is most painful? These were some of the questions asked by a bunch of 9th standard kids, while I was in Chennai. It was while answering to them, that I thought that I need to make a post on this, since a lot of other friends too have asked me the same questions in the past, last being Umar Khan from Delhi.

To try to find answers to these questions, we must travel back in time to the mid- Cretaceous period between 110 and 130 million years ago, when the first ants evolved from their ancestors the wasps according to various myrmecologists (people who study ants) like Brown, Wilson and Malyshev. Many of these primitive ants have now evolved into species that we see today and most of them exist only as fossils, but out in Australia is one such living primitive ant genera Amblyopone belonging to the subfamily Ponerinae on which myrmecologist Charles Kugler had done extensive studies to determine the nature of its sting, stinging apparatus and mechanism way back in 1978 (Fig. 2). These primitive ants use their sting for subduing live prey and for personal and colony defense.

Fig. 2: Sting apparatus of Amblyopone pallipes (Ponerinae)

When an ant from the subfamily Ponerinae stings, it grabs hold of a part of its victim’s body with its mandibles (teeth), arches its body to give it the necessary support/momentum and drives the sting downwards (Fig. 3). This is what precisely happened in my case since the procession ant belongs to the subfamily Ponerinae. That solves the mystery of how I was bitten and stung simultaneously. Most ants which have such functional sting have similar mechanism. The interesting thing though is that several of the ant subfamilies have deviated from what is described above. Ants from the subfamily Formicinae and Dolichoderinae, have lost major portion of their sting apparatus. In short, there are many ants out there which can't sting. If most of the modern day ants have lost one of their most potent weapon, the “sting”, how is it that they still are effective hunters and highly successful in fending for themselves?

Fig. 3: Ponerine way of stinging

The answer to that lies in the way ants have evolved. Primitive ants that first evolved were solely dependent on live prey and were active hunters. With evolution of the flowering plants and higher selection pressure, subfamilies like the Myrmicinae evolved to digest vegetable matter in addition to scavenged arthropods and sometimes live prey. The immediate effects of this evolutionary change would have increased the adaptability of these subfamilies to changes in the environment by letting them exploit secondary food sources in times of need, and would have thrown open a range of unexploited niches for them. With need for active hunting reduced, selection pressures for maintaining the sting as an offensive weapon would have been diminished and that could explain why many of the most dominant ant species at present do not have a well developed sting. Coming back to how these ants have made up for the loss of the sting. Take the case of harvester ants from the genera Pheidole and Pheidologeton, in which there are multiple worker class (Fig. 4). Among these are the defensive soldier class which is large, has a disproportionately larger head and crushing mandibles. They tend to stay within a small radius of the nest and are extremely aggressive towards intruders. They may sometimes accompany other foragers to take down larger prey but other than these instances, they appear to do little for the colony. 

Fig. 4: Polymorphism in Harvester ants

The Pagoda ants from the genus Crematogaster (Fig. 5), has a very unique chemical defense mechanism. The Crematogaster has a modified sting shaft at the end of which is a spoon shaped structure. This helps in holding a droplet of fluid (allomone) on the end of the sting. This fluid seems to have a repellent effect against other ants. If the droplet is applied onto an intruder, it immediately backs off and starts cleaning itself. Our very common house ant Monomorium pharaonis (Linnaeus, 1758) (Fig. 6) has independently evolved a similar chemical defense.

Fig. 5: Pagoda ant from the genus Crematogaster with the modified sting

Fig. 6: Part of a Monomorium pharaonis colony on the move

The famous Asian weaver ant | Oecophylla smaragdina (Fabricius, 1775) (Fig. 7) is totally different from the above two. They consider attack as their best defense and make up for the lack of sting with a very unique mode of attack. They are equipped with razor sharp mandibles which are shaped like a scythe. Once latched on to a hapless victim, their vice like hold doesn't let go. They attack their victim repeatedly, and pour a cocktail of chemicals the dominant of which is formic acid into the wound that causes extreme irritation. They also have an ability to spray formic acid and many a times I have been a victim myself getting formic acid into my eyes while observing them closely. They also have a very unique way of killing their prey as I had mentioned in my first post. They will stretch their victim to the limit till either they are torn apart or succumb to this torture. What hence becomes clear from this is that not all ants have sting. Ants that sting will surely bite and ants that bite may or may not sting!!!

Fig. 7: Asian Weaver ant worker in typical defensive position

Coming to the question of ant venom potency, ant venom like every other venom is protein. Extensive studies have been done on the characterization of venom in some ant genera like Solenopsis (Fig. 8) and Pachycondyla (Fig. 9). The venom of Red Imported Fire Ants | Solenopsis invicta (Buren, 1972) contains about 95% of water-insoluble piperidine alkaloids, which are responsible for the immediate swelling after being stung and many people dread the Red Imported Fire ant. These ants will appear nothing in front of the mother of all venomous ants in the world, the Jack Jumper ant | Myrmecia pilosula (F. Smith, 1858) from Australia. This particular species has been infamously called as one of the most dangerous ants of the world along with the Australian Bull ant | Myrmecia pyriformis (Smith, 1858). The venom of the Jack Jumper ant has a very potent mixture of histamines, haemolytic and eicosanoid elements. It is estimated that almost 3% of humans are highly allergic to the Jack Jumper's venom and mind you this ant is known to have killed six people in Australia in the past 20 years! So the next time someone says ants are harmless, remember to tell them about the Jack Jumpers of Australia.

Fig. 8: Fire ant Worker

Fig. 9: Pachycondyla rufipes worker

Well as usual what is the Indian and in particular Goan connect?
In India out of the 10 subfamilies of ants, eight (Dorylinae, Amblyoponinae, Ectatomminae, Leptanillinae, Proceratiinae, Ponerinae, Pseudomyrmecinae and Myrmicinae) possess stings at varying levels of specializations and among them we have the highest chances of encountering members from Ponerinae, Pseudomyrmecinae and Myrmicinae, while members of Formicinae can make up for the absence of sting with other specializations like the Asian weaver ant.
In Goa four subfamilies of stinging ants have been documented and more explorations may reveal the remaining subfamilies too. Perhaps the most notorious amongst all the ants that give a painful sting to most Goans is the arboreal bi-colored ant | Tetraponera rufonigra (Jerdon, 1851) (Fig. 10).

Fig. 10: Arboreal bi- coloured ant | Tertaponera rufonigra feeding on a frog foam egg case

The motive of this extra long post was not to scare you but to let you know that ants are extremely diverse and interesting than what is general perception. Even a small discussion on the sting of an ant can be written about for pages together. I will leave you with a video of how potent the Jumping Jack Ant of Australia can be.

Thursday, 9 October 2014

Tryst with the Trap Jaw...

You blink and you miss!!!

That's how fast the strike of the trap jaw ant from the genus Odontomachus is. Recent studies on a species of Trap- jaw ant | Odontomachus bauri (Emery, 1892) which is found throughout the tropical South America, the West Indies (except Cuba and Bahamas) and on the Galapagos Islands, have shown that they have phenomenally fast predatory strikes. These ants can shut their vice like jaws at an incredible speed, which ranges from 126–230 km/h within an average duration of 130 microseconds. If you relate it to the speed of a single blink of the human eye it is around 2,300 times faster! Well, if it’s so fast, how did scientist's manage to give us that number? It turns out to be that videography was their best friend. Scientists from the University of California and University of Illinois used a camera which can record at a speed of 50,000 frames per second with (8–11) microsecond shutter speed! Scientists have also discovered that this trap-jaw mechanism not only serves to capture prey, but to eject intruders from the nest, or jump to safety in case they meet a predator. Talk about multi functionality aeh!!!  

So what's the Indian and in particular Goan connect? Well, India too has its own share of trap- jaw ants! In India there are two genera of trap-jaw ants that are found Odontomachus and Anochetus. While recent estimates say that there are 4 species of Odontomachus and 12 species of Anochetus found in India none have been yet documented from Goa officially. A pending paper with the Journal of Threatened Taxa (JoTT) from Goa will add two species of Anochetus for the state upon being published while ongoing studies in the forests of Goa is set to add one species of Odontomachus to the Goan checklist of ants. 

Since the first live specimen of a trap-jaw ant that I had seen in Bangalore, I was fascinated with them and especially their highly modified jaws as my Professor, Dr. Chandrashekara used to always remind me that "evolutionary modifications are always at a cost".

While my journey to understand this "cost" continued, I was on a hot Sunday afternoon most surprised when a (probably) recently mated queen Odontomachus decided to fly into my house in Panjim! I had just finished experimenting how to take the white-background photographs like Alexander Wild with my then meagre point and shoot Nikon P510 with lots of eternal flashlights, CFL's, diffusers and this lady turned out to be a perfect subject for my experiment. As I was picking her up from the corner ever so gently, she didn't make any attempt to flee. I placed her in the middle of my setup and till date I remember her as my most obliging model whom I didn't have to restrain from running off. 

I will leave you with three things at the end of this post, one- the gorgeous lady's images taken in 2012, two- a simple way to differentiate an Odontomachus from an Anochetus on the field and three- an interesting video doccumenting a faceoff between an Odontomachus and an Antlion which shows that every creature, no matter how fierce or specialized in this world has a match. This video is sourced from and linked through youtube.

My attempts at doing an Alex Wild!

How to differentiate the two trap- jaw ants Odontomachus and Anochetus?

How to differentiate between Odontomachus and Anochetus?

Trap-jaw Vs Antlion. Find out who WINS!

References and More Interesting Reads:
Longino, J. T. "Formicidae: Odontomachus bauri". Retrieved October 9, 2014.

Tuesday, 7 October 2014

The Beginning...

I started my beautiful journey with "ants" years ago when I was a kid of 15 years. I was extremely fascinated when I saw a group of Asian Weaver Ants (Oecophylla smaragdina, Fabricius, 1775) fighting amongst each other. What piqued my interest was not the fact that they were fighting, but the way they were trying to kill. I still remember vividly 5 weaver ant workers holding another worker by its legs, antenna and simultaneously pulling at them till a point when the worker pulling at the antenna removed it from the worker's body. Subsequently the worker died a gruesome death with three of its legs pulled out. At that age, I was left wondering why they were fighting amongst themselves considering ants share a tight bond with each other, thanks to all the folk stories of my Grandmother (which to some extent is scientifically true) and why this killing was so ghastly. Without "Google", "Wiki" and other sources for searching anything to solve this mystery, my questions remained unanswered with my mind wandering to birds subsequently. Seven years after that incident I found myself in the University of Agricultural Sciences, Bangalore with the quest for learning about ants with renewed vigor. Today with a meager four years of studies and fieldwork trying to understand this dynamic group I stand mesmerized at the level of complexity within this group, both in terms of the evolution of their physical characters to their social set up, which varies from a parasitic life in some to mega colonies in others!
Through this blog I wish to take my readers to a journey along with me as I go exploring this amazing world of ants.
I will leave you with some photographs of the Asian Weaver ant and promise more interesting stuff soon..