Throughout the tropics, ants and Acacia trees live together in intricate interdependent relationships that have long fascinated scientists.

Now researchers are reporting that in Africa, this plant-insect teamwork depends on the very antagonist it is intended to ward off: Africa's big browsing mammals.

Researchers report that elephants, giraffes and other large plant-eaters spur Acacias to "hire" and support ants as bodyguards -- and without the mammals, the trees slash their investment in ants, opening both to other attackers.

Acacias are mostly shrubby trees common across the tropics and sub-Saharan African savannah. They have swollen thorns that serve as nests for three species of biting ants. Healthy trees have hundreds of the thorns, often containing more than 100,000 ants per tree. Both the ants and the trees benefit from their close cohabitation. The ants get the thorny shelters, as well as nectar they collect from the bases of Acacia leaves. Because the ants swarm in defense against anything that molests the trees, the trees get protection from their chief ostensible nemeses, browsing animals.

That's when the mutualism is working well. But the research got its start when Palmer noticed that certain Acacias at his research site in central Kenya, which had been fenced off from wild herbivores, looked sickly compared with their unfenced counterparts. That was the opposite of what might be expected, because the browsers feed voraciously on the trees.

Without mammals around to eat the trees, sheltering fewer, less aggressive ants would not present a cost to the trees.

But the research revealed that the fewer colonies of weakened ants become less able to defend their territory from another species of ant that, unlike the others, does not have a mutually beneficial relationship with Acacias. Instead, this fourth ant species feeds away from the tree and does not protect it from attackers -- in fact, it actually encourages a destructive, wood-boring beetle whose cavities then serve as this ant's home.

The result appears to be that the trees untouched by browsing mammals are infested with more of the beetles, which is part of the reason that they fare poorly.

One irony of the findings is that the trees have developed their mutualistic relationship with the ants to protect themselves against plant-eating mammals -- and yet because of that relationship, the trees wind up actually needing the mammals.

"If you get rid of the large mammals, it shifts the balance of power, because the trees default on their end of the bargain," Palmer said. "When the trees opt out, their hard-working employees starve and grow weak, which causes them to lose out. So, ironically, getting rid of the mammals causes individual trees to grow more slowly and die younger."

The research has important implications for conservation.

Found only on the islands of Oahu, Molokai, Maui, and Hawaii, the happy face spider, such as this one guarding its eggs on a leaf in Maui, is known for the unique patterns that decorate its pale abdomen. :)

King Solomon is said to have told sluggards to look to the hard-working ant and be wise. Aesop, too, extolled the virtues of the humble ant in his fable explaining why the insect's constant toiling through the summer months would make for an easier winter compared with the fortunes of the lazy, singing grasshopper.

Now there is another reason to admire the tiny, colonial denizens of the insect world. Ants not only work hard and are prepared to lay down their lives for their fellow ants, they also take bigger risks for the good of the colony as they get older – and they can even assess how much time they have left in life.

It is well established that worker ants tend to take greater risks as they get older. Scientists have shown that this behavioural trait benefits the colony because certain risky activities, such as foraging far from the nest, are best done by ants coming to the end of their useful lives – it doesn't pay to put young workers in high-risk jobs.

One remaining question, however, was whether ants had some internal mechanism that told them how old they were and how much time they had left before dying.

Dr Moron believed that it might be possible to manipulate an ant's lifespan artificially, and to observe changes to its risk-taking behaviour as a result. His study, published in the latest issue of the journal Animal Behaviour, did just this by increasing the concentration of carbon dioxide in a chamber housing an ant's nest. High concentrations of carbon dioxide increase the acidity of the blood and curtail an ant's lifespan.

As the scientists predicted, the worker ants in the colony began to forage further afield earlier than they would have done if they had been brought up in a low carbon dioxide atmosphere. The findings are further evidence of the apparent altruism of the ant. These workers are not only prepared to sacrifice their lives to serve and protect their queen, they also have the ability to make careful calculations of just how much risk they should take based on their current life expectancy.

Many different kinds of animals, other than ants, are known to be altruistic and the issue of how this could evolve in a world of selfish genes remained unresolved until about 40 years ago with the work of the late William Hamilton of Oxford University. It was Hamilton who showed that the altruism seen in ants and other social insects could be explained by something called kin selection.

But would the altruism of the simple ant explain human altruism? Most people show the greatest kindness to their own children, followed by the children of their closest relatives. It cannot explain the more conscious acts of true altruism that people often show to complete strangers. Human altruism may be far more complex, but the humble ant has at least given us a hint of how our own unselfish behaviour first evolved.

Related:

Ants Plug Holes to Smooth Journey.

Vanessa Alarcon saw them while working at an antiwar rally in Lafayette Square last month.

"I heard someone say, 'Oh my god, look at those,' " the college senior from New York recalled. "I look up and I'm like, 'What the hell is that?' They looked kind of like dragonflies or little helicopters. But I mean, those are not insects."

That is just one of the questions hovering over a handful of similar sightings at political events in Washington and New York. Some suspect the insectlike drones are high-tech surveillance tools, perhaps deployed by the Department of Homeland Security.

No agency admits to having deployed insect-size spy drones. But a number of U.S. government and private entities acknowledge they are trying. Some federally funded teams are even growing live insects with computer chips in them, with the goal of mounting spyware on their bodies and controlling their flight muscles remotely.

The robobugs could follow suspects, guide missiles to targets or navigate the crannies of collapsed buildings to find survivors.

A recent report by the U.S. Army Command and General Staff College warned that if traffic rules are not clarified soon, the glut of unmanned vehicles "could render military airspace chaotic and potentially dangerous."

Only recently have scientists come to understand how insects fly -- a biomechanical feat that, despite the evidence before scientists' eyes, was for decades deemed "theoretically impossible." Just last month, researchers at Cornell University published a physics paper clarifying how dragonflies adjust the relative motions of their front and rear wings to save energy while hovering.

In August, at the International Symposium on Flying Insects and Robots, held in Switzerland, Japanese researchers introduced radio-controlled fliers with four-inch wingspans that resemble hawk moths. Those who watch them fly, its creator wrote in the program, "feel something of 'living souls.' "

If such devices are being used to spy on political activists, she said, "it would be a significant violation of people's civil rights."

For many roboticists still struggling to get off the ground, however, that concern -- and their technology's potential role -- seems superfluous.

Scientists have worked out why mosquitoes make a beeline for certain people but appear to leave others almost untouched.

Specific cells in one of the three organs that make up the mosquito’s nose are tuned to identify the different chemicals that make up human body odour.

To the mosquito some people’s sweat simply smells better than others because of the proportions of the carbon dioxide, octenol and other compounds that make up body odour.

The researchers believe the discovery of the way the mosquito smells will lead to the development of a new generation of repellents that would block mosquitoes’ nose - preventing them finding humans prey - within five to 10 years.

While helping those people who always seem to get bitten and people with allergic reactions to bites, such substances could also save millions of lives in the fight against malaria, most prevalent life-threatening disease in the world.

Mosquitoes use three organs to smell and taste – a feathery antenna which can identify a wide range of different chemicals, a proboscis used for short-range detection and the maxillary palp for longer range smelling.

Malaria infects some 650 million people per year worldwide and kills between one and three million, mostly young children in Sub-Saharan Africa.

The work is part of a large international collaboration led by the US National Institutes of Health aimed at developing a chemical strategy to combat the spread of malaria in the developing world.

.. The insects aren't very good travelers either. When a truck carrying bees gets caught in a summer traffic jam, for instance, hives quickly overheat, despite the fact that the millions of workers inside them furiously fan their wings in an attempt to prevent it, says Wes Card, a beekeeper whose Merrimack Valley Apiaries in Billerica, Mass., pollinates crops from California to Maine.

"Then every minute counts," he adds, for unless the driver can quickly find a way to pull off the road and hose down the hives with cooling water, desperately hot queens emerge from their inner sanctums and typically wind up venturing into nearby colonies on the truck, where they are perceived as alien invaders and promptly killed.

One of CCD's strangest symptoms, say bee experts, is a phenomenon that might be called the madness of the nurses. Nurse bees are workers that nurture a hive's preadult bees, called brood. Workers begin their adult lives as nurses, and only during the final third or so of their six-week lives do they become foragers, venturing outside the hive to collect nectar and pollen.

Researchers have discovered that the young nurses are maintained in a kind of immature, thickheaded state by chemical signals emanating from the queen. Nurses aren't supposed to leave the hive. They're not ready to cope with the big outside world, which requires a mature bee's smarts. Besides, with nurses on leave, the all-important brood would wither.

Yet empty hives struck by CCD are often found with intact brood, which means nurses were on the job shortly before all the bees flew off forever. Beekeepers find this gross dereliction of duty much weirder than the disappearance of foragers, which essentially work themselves to death and often die outside the hive.

Says Hackenberg: "Basically, I've never seen bees go off and leave brood. That's the real kicker."

Perhaps the nurses aren't really acting crazy when they fly away. Instead, their strange behavior may represent a perfectly natural attempt by doomed workers to protect their sisters from killer microbes.

After all, a hive's workers represent a famously close-knit sorority, geared by evolution to act strictly in the best interests of their colonies. Beekeepers have long known that sick bees generally leave the hive to die, minimizing the risk that they will infect others.

To beekeepers' dismay, the farm bill recently passed by the U.S. House of Representatives, which calls for $286 billion to be spent over the next five years on everything from school snacks to biofuels, earmarked no funds specifically for CCD research.

Related:

Are The Bees Dying off Due to Stress?

Vanishing honeybees mystify scientists.

Sep 06, Bee researchers close in on Colony Collapse Disorder. (Physorg.com)

Somewhat related:

How drones find queens: Odorant receptor for queen pheromone identified.

Are bees dying because factory farms are "overworking" them? California bee farmers who let their hives take it easy find their colonies are thriving.

Honey is just one product of those highly productive bees; the pollen and wax they produce are valuable, too. Exploiting them -- making use of everything possible -- is another lesson from boutique farmers.

Commercial beekeeping has come to resemble other kinds of factory farming. Beehives are crammed close together in rows just a few feet apart; in the wild, a square mile supports at the most three or four hives. A wild colony's diet is diverse, comprising pollen and nectar from myriad plants. To compensate for the lack of forage around bee lots, bees are typically fed high-fructose corn syrup, the same stuff that's contributing to a human health crisis. And just like other agricultural livestock, bees become stressed when you crowd them together. They're more susceptible to diseases and parasites, less able to function naturally.

In nature, most flowers don't get pollinated. But you don't get a billion-pound harvest by letting nature take its course. The agribusiness way is to rent hives for the two-week almond pollination season. This year, growers paid $150 per hive, placing three to five hives per acre.

The natural lifecycle of a bee colony follows the seasons, with a hibernationlike rest period during the winter. Unfortunately for the bees, the lucrative almond pollination season comes at the worst possible time, around Feb. 10, a miserably rainy time of year. A colony may rear ten to 12 generations of bees in a year. The "winter bees" must survive the cold months and live long enough to raise the vigorous new brood that will bring back the spring pollen and begin the cycle again.

Malnutrition could be another piece of the syndrome known as Colony Collapse Disorder. Wild bees live on water, nectar, and pollen. Nectar provides the carbohydrates they use for energy and to make honey, while pollen is a rich mix of protein, fats, minerals, vitamins, and micronutrients. Bad weather may have destroyed some nutrients vital to the bees as well, making the pollen useless to their bodies.

Qualls thinks inbred queens are another possible factor in collapsing colonies. Maybe that's what happened to Peter Scholz. In every winter, the colony he has in his backyard dwindled away -- or, you could say, collapsed. Scholz gave up, but left the hive in place. Two springs ago, a feral swarm moved in. This colony is thriving, and he expects to get 50 pounds of honey this year. "It makes sense in a Darwinian way that the hives that flourish locally and swarm are the ones you want to adopt," he says.

Swarming is the natural process by which a colony reproduces itself. Capturing swarms is a popular pastime for backyard beekeepers -- and it may provide insurance against whatever disasters are befalling commercial operators.

Related: Vanishing honeybees mystify scientists.