"Oecophylla smaragdina can carry more than 100 times its own body weight while upside down on a smooth surface, thanks to its sticky feet." Image: Thomas Endlein, University of Cambridge via NewScientist

NewScientist posted photographs from the competition held by the UK’s Biotechnology and Biological Sciences Research Council to showcase images of their latest research. In a single iconic image, the first one shows the weight that an ant is capable of carrying and how strong the suction devices in her feet are.

I have blogged about these adhesive devices in the ant’s feets before (called arolia in leet speak, singular arolium), and the very first image I used back then happens to be from the same ant species in the image above.

Foot of a Oecophylla smaragdina worker. Pretarsal claws and manubrium in red; arolium in yellow; tarsi in green (Scanning Electron Micrograph, Roberto Keller/AMNH)

(h/t to P. Beldade)

In the past couple of days I have been doing some background literature research on the topic of insect walking. What I did not know is how big this field is compared to other topics in entomology. The reason behind this popularity is, unsurprisingly, the fact that the results of such research have a direct technological application: robotics. In particular six legged robots or hexabots (they should be called something like hexapodbots, but I guess the shorter name is cooler).

There are simple good reasons to go for six legs if you want to design a walking apparatus. Think on how many times when you go to sit down at the coffee shop you spend the first couple of minutes folding whatever piece of paper or cardboard you find around in order to place it underneath one of the legs to stop the four-legged table from wobbling. But you never had to do that for three-legged tables. That is because three legs are just the right number to stop whatever they support on top from moving in any dimension. Take one leg out and your table will fall following a straight arch path. Add one leg and your now four-legged table has usually more than one way to rest on three supporting points. Three legs is the most stable arrangement.

OK, but why six legs then? Because with that number you can always leave three legs firmly on the ground while you move the other three, which makes for a very stable walking. One in which the body can be kept at the same height plane while traveling forward, something insects do most of the time while walking.

Most of the research on insect walking uses stick insects and cockroaches as test subjects, and involves putting the animals to walk on treadmills to observe the pattern of leg movement under different conditions of speed, inclination, etc and, for example, immobilizing (our cutting) one or more legs to see how the movements are adjusted. A big part also involves figuring out the nervous circuitry responsible for coordinating all those legs.

I have to say, it is all fascinating and cool, but it is useless cool for what I am interested in that is, you guessed, leg anatomy and simple biomechanics (what muscle moves which skeletal piece). At the end I realized that going back to basic comparative anatomy is all I need for now. And for that Robert E. Snodgrass never fails me.

Don’t expect this blog to pick up in speed anytime soon though, but I’ll keep you entertained from time to time dear readers.

Moldovan photographer, Bolucevschi Vitali, has won the title of CIWEM’s Environmental Photographer of the Year 2009. His picture, Talking About Stars, also won the Natural World category. Only 24 years old, the amateur photographer described how he was able to take his winning image: “On a sunny day I took a camera and set out to photograph something of the life of ants. At first I was no good as the ants moved very quickly and I was easily distracted. But gradually I was drawn to a group which was climbing up a nearby dandelion. They would each pull out one seed and then parachute to the ground”

They are Formica ants or “wood ants”. Can’t tell which species from here.

via CIWEM Environmental Photographer of the Year 2009 competition winners – Telegraph.

Update September 16th, 2009: A friend of mine ask me if the ants were really parachuting and if I had heard of this behavior before. The answer was that I had never heard of this before, but my guess is that the ant just pulls the seed out forcefully and falls to the ground, seed in mouth, as it looses her balance. A beautiful accident.

The Alhambra in Granada, Spain.

I recently traveled to Andalusia, in the southern part of the Iberian Peninsula, to meet fellow myrmecologists Christian Peeters, from the Université Pierre et Marie Curie, and Alberto Tinaut, from Universidad de Granada. The reason for my trip was that I am fortunately enough to have been invited to collaborate in one of their ongoing projects studying the native ant species Monomorium algiricum. We set out to collect some colonies of this species as well as some others in the genus.

This was quite a pleasant trip. Collecting was a success, our host treated us well, and the scenery was great. The historic center of Granada is remarkable beautiful and, to my surprise, the locals speak a language very much like Spanish, for which I am accidentally fluent.

Sierra Nevada, southern face. The collecting site for M. algiricum is at the center of the picture on the mountain slope far back.

The species we are studying is also quite charming. Monomorium algiricum was originally described in the 1950s from a population in northern Africa, but the species happens also to be well established on the European side of the Mediterranean sea at mid-elevation in the Sierra Nevada, near Granada. Peculiar about this species is that the queens never develop wings, having a rather reduced thorax that very much resembles the worker’s. In general, such reproductive individuals are termed ergatoid queens, that is, worker-like queens (for ergatos = gk. worker).

The wingless thorax in the ergatoid queen of Monomorium algiricum.

Flightless queens pose a tremendous change in strategy when it comes to how the colony reproduces. The textbook version of an ant colony’s life cycle entails a newly emerged winged queen leaving the maternal nest and flying away by herself to find a suitable bachelor (or a suitable party of them). After mating, the queen sheds her wings and burrows into the ground to start a new colony by raising the first generation of workers, also by herself, without ever leaving the nest. The queen is able to perform this “claustral” colony founding by burning up her fat bodies together with the huge wing muscles to produce the energy necessary to lay eggs and feed the growing larvae. Most species of the  ~400 known in the genus Monomorium more or less display this mode of colony reproduction. By contrast, reproduction in species with ergatoid queens entails a process of colony budding: the newly mated flightless queen goes out of the maternal nest for a casual walk with some of the workers and never comes back, settling nerby to start a new independent colony. Together with the loss of wings, ergatoid queens lack the flight musculature normally used as body reserves, so they depend on the help provided by the accompanying workers to procure food and raise further generations of workers.

Collecting Monomorium subopacum in the Mediterreanan coast. Christian Peeters (standing) and Alberto Tinaut.

Christian Peeters has devoted more than two decades studying the various aspects of these “alternative” modes of colony reproduction that correlate with different queen morphologies, for which ergatoid queens are just one type among many. A major result of his extensive work is that the textbook caricature of colony life cycle I just described¹ is anything but the norm. Moreover, during their evolutionary diversification ants have deviated from the “normal” mode of reproduction multiple times independently in an astonishing high degree. Within Monomorium alone, the evolutionary switch from winged queens to ergatoid ones has probably occurred multiple times. The biology of ergatoid queens in Monomorium is better known for the North American species after the pioneering work done by William Morton Wheeler in the early 1900s, therefore the interest in the Mediterranean M. algiricum.

Collecting complete live colonies of Monomorium (Note: the hole was NOT done with the aspirator).

But, what’s in all these for me, a person more interested in the homology of obscure body structures than in colony reproduction dynamics and adaptation scenarios (hell, adaptation is not even in my vocabulary)? Well, it is exactly the fact that changes in colony reproduction strategy in ants is intimately linked to changed in the morphology of the reproductive individuals. As in the case of ergatoid queens, these morphological changes can be dramatic. These adult forms are not like workers, nor like the usual winged queens. These forms correspond to completely different castes and come with their unique anatomical specializations.

Colonies will normally have multiple queens. We want to know exactly how many there are per nest.

Just within Monomorium, the morphology of ergatoid queens is quite variable. For example, in the the North American wingless forms it is possible to homologise most thoracic plates with the ones in the thorax of a flying individual, even though the plates are fused together. But in M. algiricum the sutures between the much reduced skeletal parts are completely gone, and one has to guess what corresponds to what by careful examination of the faint depressions on the cuticle and the internal attachment of some of the muscles left.

Tinaut's lab in Granada's University. Peeters performs dissections to check how many queens have been inseminated and if their ovaries are active.

What we hope to do is to assemble a detailed picture of the life history of M. algiricum from many different angles and so understand how does this species fits into the larger pattern of the evolution of ergatoids in the genus.

Notes