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Video Captures Young Mosquitoes Launching Their Heads To Eat Other Mosquitoes

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A kind of teenager mosquito can suddenly shoot its head forward from its body — stretching its neck into a skinny cord — to bite into another youngster. And that’s just one of the ways young mosquitoes kill other mosquitoes, a new study shows.

Over decades, scientist-cinematographer Robert Hancock and colleagues have filmed attacks by these Psorophora ciliata and two other kinds of predatory mosquito larvae in unusual detail. Launching heads evolved independently in two of the kinds, he and colleagues say in their new study.

The third predator, a kind of Sabethes mosquito larva, uses its other end. Hanging head down in water, it needs only 15 milliseconds to grip prey with a hooking sweep of the breathing tube on its predatory butt, the researchers report October 4 in Annals of the Entomological Society of America.

The most dramatic pounce on film may be the neck-stretching snatch by the Psorophora larva. It might power this lunge by squeezing a rush of fluid to the head. When Hancock watches the mosquito’s body, segmented a bit like a string of alphabet-block beads, he can see two segments scrunching inward “accordion-like,” as if squirting fluid forward as the head shoots out.

Launching the head to reach the prey is one thing, but catching hold is another problem. The newly released video gives a clear view of a pair of brushes, one on each side of the head, that help with the grasp. As the head nears its victim, the brushes fan out into what the researchers call a “flimsy basketlike arrangement” that folds around the doomed prey.

Such an attack may startle people thinking of mosquito bites just as stealthy hypodermic blood-sucks. That’s the adult bite from females craving a nutritional supplement for egg-laying. Mosquito eggs, however, hatch in water, and larvae don’t assume their dandelion-wisp flying form for weeks. During the aquatic phase, these larvae don’t look, or dine, like adult forms at all.

Larvae don’t bite people, and many just filter out edible crumbs afloat in water. The meat eaters, however, pounce so fast that the human brain can’t parse it. Hancock has been fascinated ever since he was in a class in the 1980s seeing only a blur through the microscope as he tried to describe the feeding behavior. The Toxorhynchites mosquitoes that frustrated him then have turned out to be one of the groups that evolved head-launching larvae.

Mosquito larvae don’t look anything like their adult counterparts. And unlike adults, the young insects are voracious meat eaters, often preying on other mosquito larvae. Now, high-speed video reveals those hunts in new detail. In the first clip, a Psorophora mosquito larva launches its blocky head to snare a different mosquito species snack. In the second clip, a Sabethes larva uses the breathing tube on its butt to hook a meal.

If there’s any mosquito for all the mosquito haters to actually maybe not love but like, it’s Toxorhynchites,” says Hancock, now at Metropolitan State University of Denver. As iridescent adults they’re vegans, feeding largely on flower nectar. For larvae, it’s all meat, mostly other mosquitoes. Plus, he says, “They’re large, and they’re gorgeous.”

The new study found that the launch doesn’t extend as far as a head length, but Toxorhynchites attacks the prey larva vigorously. In the videos, “by the time you would catch sight of it, there would be like a half of larva … as it shoved this thing in like it was a hot dog eating contest,” Hancock says. 

He and colleagues also caught on film a third kind of meat-eating mosquito, Sabethes, which are more flexitarian than carnivore. They still eat their meat at their head end, but the danger of getting snagged comes from their rear, the researchers’ videos show. Like many mosquito larvae, they often dangle head down in the water, taking in oxygen through a flexible siphon. It turns out that the breathing tube doubles as a type of food hook, capable of snaring a target in only several milliseconds.

“The thing about Sabethes is that they’re probably more like murderers because they really don’t ingest and consume entire prey larvae like the other two,” Hancock says. Feeding tests show that the insects do gain at least some nutrition from the nibbling.

A human watching the larvae hunt may wonder why we put so much money and chemistry into trying to kill the pests when their own tiny relatives do it so brilliantly. For one thing, mosquito larvae stay underwater, says entomologist Don Yee of the University of Southern Mississippi in Hattiesburg, who wasn’t involved in the study. The two neck-stretcher groups can’t lift into the air and fly to the next water-filled tire or tree hole. There, a Toxorhynchites, for instance, “likely would consume all other larvae,” he says. “[H]owever, there may be hundreds of such containers in the area.”

In contrast, the neck-stretching Psorophora mosquitoes live in larger bodies of water and could theoretically have more of an effect at knocking back mosquito numbers, Yee says. But under natural circumstances, the predators are unlikely to crash mosquito populations as humans would want. Yee compares it to the African savanna. In photos, “you can see how many wildebeest there are. The lions can’t really control them.” In nature, after all, predators that thrive don’t wipe out their own prey.

Animals

Insect Swarms Might Generate As Much Electric Charge As Storm Clouds

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You might feel a spark when you talk to your crush, but living things don’t require romance to make electricity. A study published October 24 in iScience suggests that the electricity naturally produced by swarming insects like honeybees and locusts is an unappreciated contributor to the overall electric charge of the atmosphere.

“Particles in the atmosphere easily charge up,” says Joseph Dwyer, a physicist at the University of New Hampshire in Durham who was not involved with the study. “Insects are little particles moving around the atmosphere.” Despite this, the potential that insect-induced static electricity plays a role in the atmosphere’s electric field, which influences how water droplets form, dust particles move and lightning strikes brew, hasn’t been considered before, he says.

Scientists have known about the minuscule electric charge carried by living things, such as insects, for a long time. However, the idea that an electric bug-aloo could alter the charge in the air on a large scale came to researchers through sheer chance.

“We were actually interested in understanding how atmospheric electricity influences biology,” says Ellard Hunting, a biologist at the University of Bristol in England. But when a swarm of honeybees passed over a sensor meant to pick up background atmospheric electricity at the team’s field station, the scientists began to suspect that the influence could flow the other way too. 

Hunting and colleagues, including biologists and physicists, measured the change in the strength of electric charge when other honeybee swarms passed over the sensor, revealing an average voltage increase of 100 volts per meter. The denser the insect swarm, the greater the charge produced.

This inspired the team to think about even larger insect swarms, like the biblical hordes of locusts that plagued Egypt in antiquity (and, in 2021, Las Vegas (SN: 3/30/21)). Flying objects, from animals to airplanes, build up static electricity as they move through the air. The team measured the charges of individual desert locusts (Schistocerca gregaria) as they flew in a wind tunnel powered by a computer fan. Taking data on locust density from other studies, the team then used a computer simulation based on the honeybee swarm data to scale up these single locust measurements into electric charge estimates for an entire locust swarm. Clouds of locusts could produce electricity on a per-meter basis on par with that in storm clouds, the scientists report.

Hunting says the results highlight the need to explore the unknown lives of airborne animals, which can sometimes reach much greater heights than honeybees or locusts. Spiders, for example, can soar kilometers above Earth when “ballooning” on silk threads to reach new habitats (SN: 7/5/18). “There’s a lot of biology in the sky,” he says, from insects and birds to microorganisms. “Everything adds up.”

Though some insect swarms can be immense, Dwyer says that electrically charged flying animals are unlikely to ever reach the density required to produce lightning like storm clouds do. But their presence could interfere with our efforts to watch for looming strikes that could hurt people or damage property.

 “If you have something messing up our electric field measurements, that could cause a false alarm,” he says, “or it could make you miss something that’s actually important.” While the full effect that insects and other animals have on atmospheric electricity remains to be deduced, Dwyer says these results are “an interesting first look” into the phenomenon.

Hunting says this initial step into an exciting new area of research shows that working with scientists from different fields can spark shocking findings. “Being really interdisciplinary,” he says, “allows for these kinds of serendipitous moments.”

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Honeybees Order Numbers From Left To Right, A Study Claims

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Like many humans, honeybees seem to prefer their numbers ordered from left to right.

Honeybees trained to recognize a specific number tend to fly left when given two side-by-side options of a smaller number and right when the options represent a larger number, a new study claims. The finding suggests that honeybees have a “mental number line” and that this association has biological roots, researchers report October 17 in the Proceedings of the National Academy of Sciences.

While some scientists agree that the study makes a compelling case for a mental number line in honeybees, others argue that the new work is an oversimplification of complex human behavior.

Many humans have a mental number line that often puts smaller numbers on the left and bigger numbers on the right — if asked to organize several bunches of grapes by size, you’d likely line them up by increasing number of grapes from left to right. Whether this association is present at birth or learned later in life has long been a subject of debate.

Previous work has shown that honeybees can count, and that they even understand the concept of zero (SN: 6/7/18). “When you realize all these facts, an obvious question [is whether honeybees have] the so-called mental number line,” says Martin Giurfa, a biologist at the Université Paul Sabatier in Toulouse, France. Working from home during COVID-19 lockdowns, Giurfa tested 134 honeybees (Apis mellifera) on their number-ordering abilities using a design developed with researchers who had done similar experiments with chicks and human babies (SN: 1/29/15).

First, Giurfa had to teach his bee pupils to recognize numbers. Using sugar water, he lured honeybees into a testing chamber built from a repurposed wine box. For each bee, he hung a panel on the back of the box with a certain number of symbols on it — one, three or five — and fed them the sugar water so they’d learn to associate the number with food. By varying what the symbols looked like between visits, he ensured the bees were learning the number itself and not certain shapes or arrangements.

After 30 trips to the box, it was time for a test: Giurfa removed the training panel and set up two, mirror-image panels, one on the left wall of the box and one on the right. These new panels either had the same number of symbols as the training panel, fewer symbols or more.

Which panel did the bees fly to — left or right? “It depends on your reference number,” Giurfa says. Of the bees trained on “one,” 72 percent flew to the “three” panel to the right, but of the bees trained on “five,” 73 percent went to the “three” panel to the left. “That’s exactly the concept of the mental number line,” Giurfa says. “You align numbers based on your reference.” If the test number was the same as the training number, the bees showed no preference for left or right.

These experiments “make a very compelling case” for a mental number line in honeybees, says Felicity Muth, a biologist at the University of Texas at Austin who was not involved with the study. “They have a number of controls that really rule out any of the alternative explanations I can think of.”

Giurfa believes these results show that mental number lines, or at least some component of them, are present across the animal kingdom. However, not everyone is convinced.

“The oversimplification of complex human concepts, such as that of ‘number line,’ must be avoided, since they severely distort the reality of the phenomena that make them possible,” says Rafael Núñez, a cognitive scientist at the University of California, San Diego.

Núñez, who coauthored an article critical of the earlier chick study, thinks animal research should address why bees and chicks would have inborn mental number lines while some human groups, like those he’s studied in Papua New Guinea, don’t. Giurfa acknowledges that culture plays a role in explaining why not every adult naturally orders numbers from left to right, but feels that the proof is there for a biological underpinning (SN: 8/23/21).  

This study stops short of explaining why the brains of bees, chicks and babies have all converged on the same left-to-right number ordering but does offer a possible answer — their asymmetrical brains. All three have brains that process information differently on the left and right sides. “It might be an inherent property to these lateralized brain systems,” Giurfa says.

A shared system for organizing numbers, if truly widespread, would highlight how surprisingly similar animal minds can be to our own. Though some cognitive powers seem to be uniquely human, Giurfa thinks there is danger in dismissing the abilities of animals. “We are different from animals in some aspects,” he says, “but we are very similar in others. Denying this similarity is not what will help us understand what we are.”

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Some Seabirds Survive Typhoons By Flying Into Them

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Some seabirds don’t just survive storms. They ride them.

Streaked shearwaters nesting on islands off Japan sometimes head straight toward passing typhoons, where they fly near the eye of the storm for hours at a time, researchers report in the Oct. 11 Proceedings of the National Academy of Sciences. This strange behavior — not reported in any other bird species — might help streaked shearwaters (Calonectris leucomelas) survive strong storms.

Birds and other animals living in areas with hurricanes and typhoons have adopted strategies to weather these deadly storms (SN: 10/2/15).  In recent years, a few studies using GPS trackers have revealed that some ocean-dwelling birds — such as the frigatebird (Fregata minor) — will take massive detours to avoid cyclones.

This is an understandable strategy for birds that spend most of their time at sea where “there is literally nowhere to hide,” says Emily Shepard, a behavior ecologist at Swansea University in Wales. To find out whether shearwaters also avoid storms, she and her colleagues used 11 years of tracking data from GPS locators attached to the wings of 75 birds nesting on Awashima Island in Japan.

By combining this information with data on wind speeds during typhoons, the researchers discovered that shearwaters that were caught out in the open ocean when a storm blew in would ride tailwinds around the edges of the storm. However, others that found themselves sandwiched between land and the eye of a strong cyclone would sometimes veer off their usual flight patterns and head toward the center of the storm.

Of the 75 monitored shearwaters, 13 flew to within 60 kilometers of the eye — an area Shepherd calls the “eye socket,” where the winds were strongest — for up to eight hours, tracking the cyclone as it headed northward. “It was one of those moments where we couldn’t believe what we were seeing,” Shepard says. “We had a few predictions for how they might behave, but this was not one of them.”

The shearwaters were more likely to head for the eye during stronger storms, soaring on winds as swift as 75 kilometers per hour. This suggest that the birds might be following the eye to avoid being blown inland, where they risk crashing onto land or being hit by flying debris, Shepard says.

While this is the first time this behavior has been spotted in any bird species, flying with the winds could be a common tactic for preserving energy during cyclones, says Andrew Farnsworth, an ornithologist at Cornell University who was not involved in the study. “It might seem counterintuitive,” he says. “But from the perspective of bird behavior, it makes a lot of sense.”

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