Monthly Archives: December 2013

How Locusts Learn to Be Part of a Swarm

A strange thing happens when desert locusts get crowded together. They undergo a Jekyll and Hyde transformation.

In their solitary phase, locusts are unassuming insects. Their brown-green bodies are camouflaged to blend into the background and they walk slowly with a low, creeping gait. They generally avoid other locusts unless they are mating — or if they are forced together by food shortage. When this happens, the crowding of solitary locusts together induces a change. The insects transform into what’s known as their gregarious phase. Gregarious locusts are colorful, move faster, and are attracted to other locusts. It is in this phase that locusts form the oppressive swarms that can blacken the skies and decimate crops.

The solitary and gregarious phases differ in their looks, behavior, and life history, but do they also differ in their learning and memory capabilities? The learning and memory capabilities of animals are often adapted to their particular ecology and life history. This could be problematic, however, for an animal like the locust in which adults can transform from one phase to another; memories that are adaptive for a solitary lifestyle may not serve the insect in its gregarious way of life.

Tasteful Memories

Patrício Simões, Jeremy Nivens, and Swidbert Ott decided to investigate how locusts learn and what they remember . They used an associative training technique: First, they paired an odor (like lemon or vanilla) with another stimulus (like food). Then they presented the learned odor and another odor at the two ends of a Y-shaped maze and recorded which arm of the maze the locust chose to walk down.

When an odor was paired with a food reward, all the locusts, regardless of phase, were able to learn the association. But the researchers found a difference between the phases when an odor was paired with a toxic food. Solitary locusts learned this association right away, avoiding the odor associated with the toxic food on the first test. Gregarious locusts did not avoid the odor until several hours later.

Simões, Nivens, and Ott repeated the experiment with solitary locusts that had been crowded for 24 hours, and so were in the early stages of the gregarization process. These locusts were able to learn the positive association between an odor and food, but they showed no aversion to the odor paired with the toxic food at any time point tested. Their ability to form an aversive memory was blocked completely. And this failure in learning was specific to the aversive association, not reflective of a general impairment in learning.

The researchers hypothesize the delay in aversive learning in gregarious locusts is a consequence of the different ways in which the two phases form aversive memories. “We think that faster aversive learning is mediated by taste,” says Jeremy Niven. “The solitary locusts taste the bitter compound in the food and form an aversive memory. On the other hand, the gregarious locusts bypass the taste and only form aversive memories when they have ingested a toxic compound, and it’s this need to ingest the compound that causes the delay.”

This difference seems to relate to the different lifestyles of solitary and gregarious locusts. The solitary locusts dislike the taste of bitter compounds. The ability to quickly form aversive associations should help solitary locusts avoid ingesting toxins. But in their gregarious phase, locusts actually seek out some plants containing bitter compounds to make themselves distasteful to predators. In this case, the lack of a rapid, taste-mediated aversion to bitter compounds helps the gregarious locusts eat the bitter plants they need to defend themselves. Recently crowded locusts, the ones in the early stages of gregarization, seem to lack the ability to form aversive associations altogether. This allows them to eat greater amounts of bitter compounds without forming aversive memories.

A Plague of Learning Locusts

Finally, the researchers looked at how this might work with the real-world case of hyoscyamine (HSC), a toxic alkaloid found in some plants native to the locusts’ habitat. Solitary locusts avoid plants containing HSC, but gregarious locusts prefer them and seek them out. In tests, solitary locusts avoided an odor associated with HSC, whereas gregarious and recently crowded locusts tended to approach it.

This seems like it would pose a problem for a solitary locust that learns to associate an odor with food containing HSC but then undergoes gregarization. As a gregarious locust, it would need to seek out and eat plants containing HSC. What mechanism allows these locusts to start to eat the toxins they need?

Simões, Nivens, and Ott took solitary locusts that learned an aversive association between HSC and an odor, crowded them to induce gregarization, and then exposed them to the odor-HSC pairing a second time. When tested in the Y-maze, these locusts no longer avoided the odor paired with HSC. This demonstrates that recently crowded locusts can update their memories upon re-exposure to the same stimulus. The experience of crowding alone transforms a further exposure to the odor-toxin pairing from an aversive experience to a positive experience that overrides their previously formed aversive memory. “This provides the means for the solitary locusts to switch their memories, helping them to adopt a new gregarious life history,” says Niven.

The crowded conditions that induce gregarization in locusts also produce an intense competition for food. Gregarious locusts eat all available plants in their path, but they preferentially eat plants with toxic compounds to become unpalatable to predators. Simple learning mechanisms, combined with hunger and competition for food, allow locusts undergoing gregarization to update and override previously formed aversive memories when they are re-exposed to the same stimuli. They effectively retrain themselves: locusts driven to hunger by overcrowding eat the plants containing HSC. But during gregarization, aversive memory formation is blocked. So they form a new, positive association with the odor they previously association with an aversive toxin.

“We think the mechanisms we’ve uncovered provide a means for the solitary locusts to be able to change phase and still behave appropriately,” Nivens says. They allow solitary locusts to make a complete transformation — in looks, behavior, and learning — to become part of a ravenous swarm.

Colorful Tree-Climbing Tarantulas Found in Brazil

Tarantulas really are ancient beautiful spiders. They have found some that are members to a previously thought extinct genus. Their feet are really cool when you hold them!

According to Andrew Zimmern, the big ones taste similar to shellfish… I’ll take his word for it.

http://www.livescience.com/24408-arboreal-tarantulas-new-species.html

Image Via: http://i.livescience.com/images/i/000/032/842/i02/tarantula1.jpg?1351633413

How Many Species of Cockroaches Plague Humanity?

How Many Species of Cockroaches Plague Humanity?

Photo: *saipal

Cockroaches are one of the most successful species on the planet. They are also one of the most hardy and one of the most common pests. Cockroaches first landed in the Americas from Africa as early as 1625, but the invasion is far from over.

New York City, for example, just identified a new breed of immigrant: a novel species of cockroach with a heightened cold tolerance. As Reuters reportsPeriplaneta japonica normally resides in Japan, but an exterminator spotted one last year in the High Line park. Now, entomologists have confirmed the sighting—the first ever in the U.S. for this species. In the Southwest, an invasive species of cockroach with a fast developmental period and the ability to produce more eggs is outcompeting “native” cockroaches, introduced long ago from Africa and assimilated into the environment, the Los Angeles Times says. For Southwesterners, the good news is that the invasive Turkestan roaches cannot climb walls. The bad news is that they reproduce very quickly, and an invasion can swiftly escalate out of control.

So with Turkestan roaches and Japanese roaches now calling North America home, how many cockroaches do we now have to worry about?

There are actually 4,500 species of cockroaches in the world. But just 30 are considered pests. Of those 30, however, four especially excel at making a nuisance of themselves: the German, American, Australian and Oriental cockroaches.

Unfortunately, all four of those species occur in the U.S. German cockroaches are most common, but it’s the American cockroaches—the largest and most limber of the pest species—that really get the heart thumping when they scuttle across the floor. Australian cockroaches originated from Asia and resemble American cockroaches: they are a bit smaller, but just as adept at erratically flying at your face or hanging from your ceiling. Out all of these detestable contestants, however, it is the smaller oriental cockroach that should cause the most alarm. As frequent sewer dwellers, they are considered to pose the greatest sanitation threats.

More from Smithsonian.com:

Cockroaches Have Evolved to Avoid Our Traps 
Cockroaches Stick to Different Neighborhoods Just Like New Yorkers Do 

The Infested Mind: An Entomologist’s Crippling Fear of Insects

On July 11 th 1998, my life was ominously transformed by an encounter with the once-familiar subjects of my research. Having been hired by the University of Wyoming a decade earlier to study the ecology and management of rangeland grasshoppers, I thought that I pretty much knew these insects.

I had spent that fateful morning gathering data from research plots. A week earlier, my field crew reported that to the north, where deep draws were etched into the prairie, the grasshoppers were reaching biblical proportions. I decided to see for myself.

The earthen banks rose above my head as I descended into the gulch, where the insects had massed into a bristling carpet of wings and legs. My arrival incited pandemonium. Grasshoppers ricocheted off my face, tangled their spiny legs into my hair, and began to crawl into the gaps between shirt buttons.

A Nightmare Come True

In a recurring nightmare from my childhood, a swelling, suffocating amorphous mass inexorably filled my room. By time I reached adolescence, this dream became less frequent. As an adult, the only echoes were a vague discomfort in crowds, an intense reaction to Hitchcock’s The Birds , and a persistent fascination with the concept of infinity—until that nightmare metamorphosed on the Wyoming prairie.

After frantically sweeping the grasshoppers from my body and scrambling back to the truck, the blind, irrational, unaccountable terror receded. I tried to forget what had happened. But I couldn’t.

I was an entomologist, and this was like a riveter on a skyscraper suddenly experiencing a debilitating dread of heights. What happened in that rangeland draw challenged my rationality and, to be honest, my mental health. And when a scientist is bewildered, there’s an obvious response: research. My hope was that by understanding the infested mind, I could engage in psychological pest management.

Pests on the Brain

The first task of a researcher is to clarify fundamental concepts—I had experienced fear and was wrestling with anxiety. Fear is the heart-pounding response to present danger, and anxiety is the disquiet that comes from anticipating danger. I figured that if I could master my straightforward fear, the troublesome anxiety would vanish.

But fears can be messy, having both proximate and ultimate manifestations . For example, a person frightened by cockroaches (proximate) might believe they will invade her body (ultimate). Or a person who blanches among thronging grasshoppers might harbor an existential dread of being overwhelmed. Moreover, a simple fear can “spread” into a pool of anxieties. The person who is afraid of cockroaches might become apprehensive about looking under the sink. Likewise a fellow frightened by a grasshopper swarm might harbor misgivings about entering gullies—and worry that he’s heading toward full-blown phobia.

About one-in-ten people develop a phobia in the course of their lives, and nearly 11 million people wrestle with entomophobia . This condition is defined as a severe, persistent, and unreasonable fear of insects or their relatives. Spiders top the list , but the runner-up is grasshoppers (followed by ants, beetles, moths, butterflies and caterpillars). So what accounts for our dread? In short, a conspiracy of nature and nurture.

The Evolution of Fear

Evolution favors anxious genes. That is, when our ancestors mistook a tumbling leaf for a spider or a grass seed for a louse, it meant nothing more than an unnecessary flinch or some pointless scratching. But mistaking a viper for a tree root meant elimination from the gene pool. From the perspective of evolutionary psychology, the cost of survival may be a lifetime of inherited discomfort.

Critics note that the objects of phobias oftentimes don’t occur in nature ( e.g., clowns ). But even if some scientists overstate the evolutionary case, it is clear that the human mind is not a blank slate. We are born with tendencies to readily learn things that favor our survival. English fits our inborn expectations of language structure; grasshoppers fit our innate template of fearful objects.

But evolutionary psychology has a few unpatched holes. We fear harmless (even downright beneficial) species. A swarm of locusts was a nutritional windfall for most of human history. From an evolutionary perspective, I should have been like a kid in a candy store.

Learned Aversion

My youthful encounters with grasshoppers were darkly enchanting. On lazy summer afternoons I’d snag a few and feed them to the black widows that colonized the cinderblock wall in the backyard of my Albuquerque home.

I don’t know what memories might have conspired to induce my panic, but psychologists contend that adult fears often reflect childhood learning via direct experience (a cockroach runs up a kid’s pant leg), modeling (a kid sees his mother scream in terror at cockroaches), and instruction (a kid’s father tells her a story about cockroaches burrowing into children’s ears).

Modern culture provides abundant opportunities to learn an aversion toward insects. Arthropods were featured on the big screen in the 1950s, with giant ants ( Them! , 1954), spiders ( Tarantula , 1955), and grasshoppers ( Beginning of the End , 1957—I knew it). In The Fly (1958, 1986), the hero’s body is melded with that of the insect and soon the chimeric character manifests the amoral tendencies of an insect. Today’s ‘reality’ shows continue the tradition of enculturating fear and loathing.

We are not clearly predisposed to either fear or love insects, evolutionary psychologists and biophiliacs notwithstanding. Insects and their kin have provided stings, bites, and infections as well as ecosystem services, scrumptious snacks, and moments of delight. In short, evolution assures that we notice these creatures, and culture shapes our responses—and our therapies.

Fixing Phobias

Specific phobias are both readily diagnosable and treatable . So why do only one in eight sufferers seek relief? Because they find workarounds. Entomophobes simply don’t go into the storage shed or look under the sink. But what if you’re an entomologist?

I returned to the field a week after my panic attack but couldn’t get closer than the edge of the gully. Realizing the absurdity of my condition, I challenged myself to give a plausible reason for fearing grasshoppers. I worked my way through what I later learned was an approximation of Cognitive Behavioral Therapy (CBT), which is sort of a “best of” album for psychological treatments. In CBT, the therapist functions as a trusted teacher, structuring a series of empirical experiments with the feared object and directing the ‘student’ to draw reasoned conclusions about the implausibility of the dreadful hypothesis. The overarching principle of CBT is to help the patient become a scientist, with the mind and body being the subjects of detached inquiry.

A trip to Australia provided the ultimate test. I asked a colleague to take me into a swarm of plague locusts “to take photographs” (I was too embarrassed to reveal my actual reason). Being engulfed by millions of insects was mesmerizing—but not terrifying. The unfathomable surge of life evoked a sense of wonder tinged with eeriness rather than a heart-pounding nightmare.

I returned to my entomological research, but it was not the same. In many ways it was better. The insects were never again merely objects of detached investigation. What happened in that draw led me ineluctably to the interface of the sciences, humanities and arts where I now reside. And I’m not afraid to say that I’m grateful.

Jeffrey A. Lockwood is the author of The Infested Mind: Why Humans Fear, Loathe, and Love Insects (Oxford University Press, 2013).

Image credit: Gucio_55 /Shutterstock

Mystery of how fire ants survive floods solved: Insects hook their legs together to form LIFE RAFTS that help them float

U.S. engineers used mathematical modelling and time-lapse photography to unravel how the fire ants self-assemble into their life-preserving raft

Tech researchers said the ants grip each other with mandibles, claw and adhesive pads at a force 400 times their body weight to make their raft

The result was a viscous and elastic material that is almost like a fluid composed of ant ‘molecules,’ and is self-healing

Incredibly, an ant raft can be assembled in less than 100 seconds

By Sarah Griffiths

PUBLISHED: 07:54 EST, 27 November 2013 | UPDATED: 10:51 EST, 27 November 2013

The mystery of how groups of fire ants survive floods has baffled biologists for decades.

But now scientists have worked out how the ants bind together in order to build a kind of raft that enables them to float ‘effortlessly’ for days.

Biologists and engineers used mathematical modelling and time-lapse photography to unravel how the fire ants self-assemble into their life-preserving raft using different body parts, including their claws and mandibles.

They found the tiny creatures linked their bodies together in a similar way to how waterproof fabric is woven.

Mechanical engineering graduate student Nathan Mlot, professor of industrial and systems engineering, Craig Tovey and David Hu, joint professor of mechanical engineering and biology, at Georgia Tech, described how the fire ants act collaboratively rather than individually to form a water-repellent, buoyant raft in the journal Proceedings of the National Academy of Sciences.

An individual ant’s exoskeleton is moderately hydrophobic so it can shrug off water, but the ants enhance their water repellence by linking their bodies together.

The researchers froze the fire ants to observe that they construct rafts when placed in water by gripping each other with mandibles, claw and adhesive pads at a force 400 times their body weight.

The result was a viscous and elastic material that is almost like a fluid composed of ant ‘molecules,’ they said.

The ants spread out from a sphere into a pancake-shaped raft that resisted submerging them in water.

‘It’s a real thrill unravelling what at first looks like chaos,’ Professor Tovey said.

‘To understand what the individual behaviours are and how they combine in order to achieve the function of the group is the central puzzle one encounters when studying social insects.’

Professor Tovey and the team tracked the ants’ travel and measured the raft’s dimensions and found the ants moved using a stereotyped sequence of behaviour.

The ants walk in straight lines, ricocheting off the edges of the raft and walking again until finally adhering to an edge, Tovey said, before explaining that the ant raft is water repellent because of the animals’ cooperative behaviour.

The ant raft provides cohesion, buoyancy and water repellence to its passengers, but even more remarkable, is that it can be assembled in less than 100 seconds.

The raft is also self-healing, so that if one ant is removed from the raft, others move in to fill the void.

‘Self-assembly and self-healing are hallmarks of living organisms,’ Professor Hu said.

‘The ant raft demonstrates both these abilities, providing another example that an ant colony behaves like a super organism.’

The research could have application to logistics and operations research and material sciences, including the construction of man-made flotation devices.

It also could impact the field of robotics, the team said.

Mr Mlot said: ‘With the ants, we have a group of unintelligent units acting on a few behaviours that allow them to build complex structures and accomplish tasks.’

‘In autonomous robotics, t hat’s what is desired – to have robots follow a few simple rules for an end result,’ he added.

How to keep pests out of your food bins!

UBC entomologist Rana Sarfaz gave CBC Radio One’s The Early Edition five ways to keep food bins free of squirmy, disgusting pests.

1. Freeze your food scraps

Put your stinkiest food waste in the freezer until the night before pick up. That gives the pests less time to take over.

2. Line your bin with paper

Newspaper or store-bought bags absorb moisture and keep the bin clean and pest-free.

3. Wrap your waste in paper

Again, this sucks up the moisture and protects the scraps from flies and their larvae.

4. Layer your bin with leaves

Use the plant waste from your yard to layer after each trip to the food scraps bin. This controls moisture and makes the scraps tough to get to.

5. Clean up after your dog

Dog waste is a fly’s favourite meal. If there’s poop on the ground near your food waste bin, the flies are sure to find their way in.

Via: CBC

It’s Only Natural: Insect Overwintering Strategies

It’s Only Natural: Insect Overwintering Strategies

A click beetle overwinters as a larva under the bark of a rotting log. (Photos by Mary Holland) When you think of something as small as a one-tenth inch bark beetle surviving a winter with temperatures that dip well below zero for days on end, it seems miraculous.

How does ice not form within its cells, causing it to die? It’s because that beetle and millions of other insects are capable of manipulating their metabolism and biochemistry to avoid freezing to death. But how do they accomplish this?

All insects are ectothermic, or cold-blooded, and thus take on the temperature of the air around them. Cold weather slows them down, and during the winter they enter a resting stage called diapause, often referred to as hibernation. During diapause their metabolism slows down and normal activities cease.

Loss of daylight triggers changes

Many insects recognize that it’s time to begin preparation for diapause by the decreasing amount of daylight in the fall. In response, they start to migrate downward, where there’s more protection from the elements—migrating from trees, shrubs, and plants down to the leaf litter, rock crevices, and in or under rotting logs and under rocks. Even in these locations, however, more protection is usually necessary to avoid freezing. Two of the methods insects use to acquire additional protection include tolerating freezing (freeze tolerant) and relying on other mechanisms to avoid freezing (freeze avoidant).

Carpenter ants in a log. Carpenter ants cluster in their galleries during the winter and produce glycerol to prevent destructive ice crystals from forming in their bodies. Freeze-tolerant insects can withstand the formation of internal body ice, whereas freeze-avoidant insects avoid freezing by keeping their body fluids liquid. In New England, where there are long periods of cold temperatures, the main strategy of most insects is freeze avoidance. This can be achieved in several ways. One is to seek out a spot where ice usually doesn’t form, such as a very dry location. Another is to create some kind of physical barrier, such as a wax coating, that protects against ice forming on the external skeleton.

Lowering the freezing point

Regardless of such strategies, all freeze-avoidant insects that can’t tolerate the formation of ice in their body fluids lower the temperature at which their body fluids freeze. A process known as “supercooling” allows water to cool below its freezing point without changing into a solid. Water needs a particle in order to crystallize, and with no such particle, it can cool down to minus 43 F. without freezing. Freeze-avoidant insects that engage in supercooling remove or inactivate all of the food particles, dust, and bacteria in their gut or inside their cells, so the fluid within their bodies can’t solidify in northern New England winter temperatures. In addition, some insects synthesize substances such as glycerol throughout their head, thorax, and abdomen. This substance acts as antifreeze, reducing the lethal freezing temperature of their bodies.

Shared shelter, but little fraternizing

This state of suspended animation, or diapause, often takes place in or just under the bark of a rotting log. The insects that seek winter shelter here often have the company of other ectothermic creatures, including spiders, snails, and slugs. For the next few months, however, there won’t be much fraternizing among them.

Mary Holland is the author of “Naturally Curious: A Photographic Field Guide and Month-by-Month Journey Through the Fields, Woods, and Marshes of New England,” “Milkweed Visitors,” and “Ferdinand Fox’s First Summer.” She has a natural history blog which can be found at http://www.naturallycuriouswithmaryholland.wordpress.com .