Category Archives: Insect

Caterpillars Can “Blink” A Fake Eye

22373_origMany animals have a fake eye — or eyespot — or two that they can use for protection from predators, often by frightening or distracting the hungry creature. Eyespots are especially common among tropical caterpillars. And researchers conducting a caterpillar inventory in Costa Rica have documented two species (Eumorpha phorbas, above, and E. labruscae) in which the eyespots can sort of blink. They report their findings in the Journal of Natural History.

How can an eye that’s not real blink? To find out, Thomas J. Hossie of Carleton University in Ottawa, Canada, and colleagues collected and reared caterpillars of the two species. When each species reaches the last instar before turning into a moth, it takes a form that has an eyespot on a tentacle that pops up from its butt; this is known as the anal horn. For the study, the researchers would remove a caterpillar from its rearing bag, let it acclimate for a minute, and then prod its rear three times. The result was a “blink,” such as the E. labruscae captured in the video below:

“Both caterpillars can ‘blink’ their posterior eyespot upon perceiving a threat,” Hossie writes on his blog Caterpillar Eyespots. “That is, they can move the skin around the eyespot such it either conceals/reveals the eyespot or flashes (i.e. reflects light) conspicuously towards an onlooker.”

Being able to blink the eye would make it look more like a mammal or bird eye, which is a little odd because scientists had thought that the eyespots on caterpillars were supposed to look more like snake eyes. Snakes can’t blink because they don’t have eyelids. Unfortunately Hossie and the other researchers haven’t been able to test how predators respond to these distinctive eyespots — including whether they might interpret them as mammal, bird, or snake — because these are really rare species.

But Hossie notes on his blog that these caterpillars have another defensive trick that is truly snakelike: “Interestingly,” he writes, “both Eumorpha caterpillars also inflate their thoracic body segments, while pulling their head into their body, to form a diamond shape which appears similar to the head shape of dangerous co-occurring snakes (at least to human observers).”

Image copyright CAPEA, used with permission under Creative Commons license

July 2, 2013Permalink Leave a comment

Fire Versus Crazy: Battle Of The Invasive Ants

Fire_ants02There’s a good chance you’ve heard of the red imported fire ant (above), a pest that’s found across the southern half of the U.S. and is now one of the world’s 100 worst invasive species. These aggressive ants, natives of South America, not only have a painful sting but also a penchant for attacking in swarms.

Less known is the Caribbean crazy ant, a more recent invader that’s been found in Florida and Texas (where it was once called the raspberry crazy ant). Unlike fire ants, Caribbean crazy ants — named for their erratic behavior — don’t have stingers and hardly bite. But infestations can be huge and incredibly hard to control. In one story from 2008, a woman describes how she kept killing and killing the ants that swarmed her house and within a week had filled a five-gallon bucket with dead ants.

News reports sometimes say that Caribbean crazy ants will attack and drive out fire ants, but there hasn’t been any scientific data that backs up the claims. So a trio of biologists from Rice and Texas A&M universities staged battles between nests of the two species. Their study appears in PLOS One.

The bad news is that, while there was no outright winner in the ant-on-ant combat, the crazy ants came off the worse of the two species; crazy ants were twice as likely to die as fire ants. It seems that the fire ants may be better equipped for a war, the scientists say. The fire ants are armed with stingers, which may be a more effective weapon than the crazy ants’ ability to spray formic acid. “It is possible that the ability to sting makes fire ants a more potent combatant than crazy ants,” the researchers write.

One odd thing that the scientists discovered is that crazy ants get more aggressive when they’re fed a low-carb diet. They even do better in battle and die less often when fighting fire ants. That’s different from most other ant species, which get more aggressive when given high-carbohydrate food. But what that means for which species wins out and spreads its misery farther, well, we’ll just have to wait and see.

Image courtesy of USDA/ARS via wikimedia

June 12, 2013Permalink Leave a comment

Did This Ant Get Makeup Advice From Johnny Depp?

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The German scientists who discovered this new species of ant in the Philippines gave it the name Cardiocondyla pirata because the blackish stripe that crosses the female’s eye is “reminiscent of a pirate’s blindfold,” they write in Zookeys. To me, though, it looks more like the insects took advice from the makeup artists behind Captain Jack Sparrow‘s heavy eyeliner.

The ants are the only ones known in the world to have this coloring, the researchers note in their paper. They discovered the species while searching for another member of the genus in which the males show great diversity of shape and behavior. During their search they came across these other ants “in the cleavage of big stones in a shady streambed,” study coauthor Sabine Frohschammer of Universität Regensburg said in a statement. “Due to the darkness of the rainforest and the translucent body parts of the tiny ants, they were nearly invisible. Under bright light and a magnifier we detected the nice stripe across the eyes and therefore always referred to these species as ‘the pirates,'” she said.

The purpose of the stripe is still a mystery. It probably doesn’t serve as a sexual signal to males of the species. Their vision is poor, and they rely more on chemical and tactile cues. And when they hook up, it’s completely dark. It’s more likely, the researchers say, that the stripe and other coloring in the female help to confuse a predator, perhaps giving the impression that the ant is actually two insects (one of the segments closer to the rear is nearly translucent). But until the scientists find a predator that has good enough vision to see the details on this ant, the purpose of the pirate’s eye stripe will remain just a guess.

Image credit: Bernhard Seifert

May 28, 2013Permalink Leave a comment

Four Unexpected Jobs For Bees

beeBees hold important jobs pollinating our crops and flowers and making yummy honey. But here’s some unexpected ways we’ve put bees to use:

1) Hunting down land mines: Nikola Kezic, a honeybee expert at Zagreb University in Croatia has been training bees to associate the smell of TNT with food by lacing their nectar with the explosive, Gawker reports. The bees haven’t been field-tested yet, but the researchers envision using cameras that sense heat to track the bees across de-mined minefields and check if they really have been made safe. Other researchers have been attempting to train bees to sniff out illegal drugs or other explosives.

2) Studying cocaine addiction: Scientists in Australia painted cocaine on the backs of bees to study how the drug changed their behavior. Like humans, the bees go through withdrawal when the drug is taken away. Bees aren’t humans, but researchers hope that by studying the insects they can gain some clues as to what’s going on at the genetic level and gain insight into human addiction as well.

3) As a weapon: There are many cases where armies took advantage of insects’ stings. Romans, those experts of war, for example, would catapult beehives at their enemies. And during the Vietnam War, the Viet Cong was known to hurl the nests of hornets and wasps (not bees, admittedly, but same effect) into enemy outposts.

4) In food: Daniella Martin at Girl Meets Bug says that adult bees can be roasted and ground into a “delicious” flour. And bee larvae are especially tasty. “Think about it, all they eat is royal jelly, pollen, and honey!” Martin writes. She says that the larvae taste like mushroomy bacon when they’re sauteed in butter.

Image courtesy of flickr user Paul Stein

May 21, 2013Permalink Leave a comment

This Moth Has Better Hearing Than A Bat (Or Anything Else)

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The greater wax moth (Galleria mellonella) is locked into a high-frequency, evolutionary battle with the bats that prey upon them. Bats emit ultrasonic for the purpose of echolocation, sending out sounds at frequencies as high as 212 kHz. Now scientists have discovered that not only can the great wax moth hear the bats’ echolocation calls, but the moths can hear even higher frequency sounds, up to 300 kHz. The research team from the University of Strathclyde in Glasgow, Scotland report their findings in Biology Letters.

Such auditory sensitivity is “unprecedented,” the scientists write. No known bat produces sounds at that high a frequency, so why the moth evolved to hear such sounds is a bit of a mystery. But the researchers suspect that the super-hearing helps the moths avoid predators or communicate with each other, perhaps in courtship.

“The use of ultrasound in air is extremely difficult as such high frequency signals are quickly weakened in air,” the lead researcher James Windmill said in a statement. “It’s not entirely clear how the moths have developed to be able to hear at such a high frequency, but it is possible that they have had to improve the communication between each other to avoid capture from their natural predator – the bat – which use similar sounds.”

Image courtesy of Sarefo via Wikimedia Commons

May 9, 2013Permalink Leave a comment

Bad News For Animals That Live In The Subnivium

voleYou’ve probably never heard of the “subnivium.” That’s because it’s a term that scientists just made up (they do that). The group of ecologists and biologists, led by Jonathan Pauli of the University of Wisconsin, say in an article recently published in Frontiers in Ecology and the Environment that the subnivium is the seasonal refuge that occurs below the snow where there’s environmental stability. It’s cold there, with temperatures near freezing, but this region serves as a retreat from the harsh, sometimes changeable environmental conditions above.

A healthy subnivium contributes to a healthy ecosystem. Insulated soil lets microbes and fungi breathe and proliferate and process organic matter. Plants benefit from increased carbon dioxide and warmer temperatures, especially during late winter and early spring. Many animals — a list that includes invertebrates, amphibians, reptiles, birds, and small mammals — will use the region to hide out during the winter, feeding off each other or any vegetation they can find. There are whole ecosystems below the snow.

But warming conditions have led to many changes in the patterns of snow in the Northern Hemisphere (that’s where most of the world’s snow is found): The month of maximum snow cover has shifted from February to January. The spring melt is about two weeks earlier than it was decades ago. The extent of land covered in snow in the winter has been shrinking. In many places, the amount of time when snow is more likely than rain has decreased by more than one and a half months. Snow depths are decreasing, as are snow packs. The list goes on and on.

“Snow cover is becoming shorter, thinner and less predictable,” Pauli said in a statement. “We’re seeing a trend. The subnivium is in retreat.”

With all these changes, the stability that the subnivium provides is therefore disappearing. What does that mean for the ecosystems that thrive there? One worry is that organisms, such as plants, that are exposed to cycles of freezing and thawing could experience tissue damage. Others, like voles or insects, that lose the layer of snow that hides them may be subject to predation by birds or other critters.

“Decay of the subnivium will affect species differently, but be especially consequential for those that lack the plasticity to cope with the loss of the subnivium or that possess insufficient dispersal power to track the retreating range boundary of the subnivium,” the researchers write. Those that can adapt to the loss of stability or can move to places where there’s still reliable snow cover will do better than others. Adapt or move — those seems to be the only two options for surviving climate change.

Image of vole courtesy of flickr user musubk

May 7, 2013Permalink 2 Comments

This Fairyfly Doesn’t Deserve Its Name

fairylandWhen you hear the name fairyfly, you probably expect something beautiful and delicate. But other than its fairyland-like habitat in Costa Rica (above), the new fairyfly species Tinkerbella nana doesn’t seem to have much to do with fairies. Here are the images provided by the scientists as they announced their new discovery in the Journal of Hymenoptera Research:

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and

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I don’t know what version of Peter Pan the researchers — from Natural Resources Canada and London’s Natural History Museum — have been watching or reading, but I never envisioned Tinkerbell quite like this.

Fairyflies are some of the world’s smallest insects, and all of the T. nana individuals were smaller than 250 μm in length. It’s pretty amazing that anyone finds them at all, let alone a new species in a dense Costa Rican forest.

Images courtesy of John T. Huber

April 25, 2013Permalink 2 Comments

Why The Leafhopper Doesn’t Break Its Leg On Takeoff

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With a name like the green leafhopper, you know that Cicadella viridis is probably going to be a keen jumper. These insects can hop with an acceleration of 152 meters per second squared — many times the acceleration of gravity, allowing a successful takeoff — and an average velocity of 0.88 meters per second. That’s only about 2 miles per hour, but it’s not a bad speed for a creature that’s just a fraction of an inch in size.

Roboticists like to study animals such as these to get ideas on how to create better robots, taking shortcuts by harnessing the “design” power of millions of years of evolution. And so researchers led by the BioRobotics Institute in Pontedera, Italy, turned to the green leafhopper to understand how the insect can jump so fast without breaking a leg or destroying the leaf from which it takes flight. Their study appears in the Journal of Experimental Biology.

The scientists collected 67 leafhoppers, a European native, from cane thickets near Pontedera. Then they filmed the insects jumping in the lab, capturing them on film at a rate of 8,000 frames per second to catch the movements in detail.

The powerful jumps are powered by muscles, but muscle-power alone doesn’t explain what’s going on. The leafhopper’s acceleration is nearly constant, which requires that the insect’s leg exert a constant force against the substrate from which it’s taking off. Muscles can’t provide that constant force, and they work too slow for a takeoff that lasts just a few milliseconds. The muscular force also reaches a high enough level that, on its own, it should break the insect’s delicate leg or punch through a thin surface like a leaf.

To translate that strong variable force from its muscles, the researchers found, the leafhopper moves its legs in such a way that the force becomes constant and the stress on both the insect and its substrate never reaches a point where it becomes damaging. That allows a successful takeoff, letting the insect avoid becoming a meal for something bigger.

Image courtesy of Hectonichus on Wikimedia Commons

March 14, 2013Permalink Leave a comment

Caffeine Buzz Helps Bees Be Better Pollinators

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Plants don’t make caffeine to help you get a morning buzz. In high concentrations, the chemical is a bitter deterrent against munching herbivores. But in smaller doses, according to a paper published today by Science, caffeine helps bees to remember a flower’s scent.

“Caffeine in nectar is likely to improve the bee’s foraging prowess while providing the plant with a more faithful pollinator,” the study’s lead author, Geraldine Wright of Newcastle University in the U.K., said in a statement.

It’s probably not a surprise to find caffeine in the nectar of species from the Coffea genus, but Citrus species also can produce caffeine, including in the nectar. In that sugary substance, the chemical is produced in a low enough dose that bees can’t taste it, but it does affect them, Wright’s group found. Using trained bees, the researchers showed that the insects were better able to learn a floral scent when it was laced with caffeine than when it only contained sucrose. And the bees remembered it for up to three days later.

This is a pretty good trick for a flower — drugging its client to return again and again, ensuring that the plant gets pollinated.

It’s not the first time that scientists have experimented with drugs on bees, though. A few years ago scientists in Australia gave cocaine to bees, but that time they had to paint the drug on the back of the insects.

 

Image Credit: Courtesy of Geraldine Wright and Science

March 7, 2013Permalink Leave a comment

Why A Dung Beetle Wouldn’t Like City Living

51924_webOne of the downsides of living in a city is that they aren’t the greatest spots for stargazing. That’s kind of sad for urban dwellers, but it would be a big problem if we were dung beetles.

That’s because dung beetles of one species, Scarabaeus satyrus, navigate using the light of the Milky Way, say researchers from Sweden and South Africa in the journal Current Biology.

Dung beetles got their name because they feed on feces (they definitely count as one of the world’s more disgusting critters). Some species, like S. satyrus, collect their dung into a ball that they roll away from the dung pile, so they can save it for later. The direction that they roll their ball in isn’t too important, but a beetle does want to make sure it rolls it away from the pile and away from potential competitors.

During the day, the insects can use the sun for navigation, but at night it can get a bit more complicated. There’s the moon, of course, but the moon isn’t always out. And that’s when a secondary light source, like the Milky Way, becomes a beacon in the sky.

Image credit: Emily Baird/Courtesy of the University of Witwatersrand

January 29, 2013Permalink Leave a comment