On August 6th, 2018 we learned about

Specific levels of light pollution matter to nocturnal predatory insects

I admit that sometimes we leave our porch light later than we need to. It somehow seems friendlier to our neighbors to share a little light with the folks on our street, and only a few moths ever seem to get confused or distracted by the glow of the single bulb near our door. Of course, since we’re not the only family on the street to do this, the cumulative effect can be much greater than what we notice on our porch— scientists have been finding that humanity’s propensity to shine a light anywhere and everywhere is causing a lot of problems for animals that evolved to live under the darkness of night. The effects of light pollution aren’t always easily predictable, with some species behavior shifting dramatically depending on the exact amount of light they’re lit by.

Brighter isn’t better

While we usually associate porch lights with moths alone, half of all insect species are nocturnal, so there’s a lot of possible outcomes from growing levels of light pollution. Parasitoid wasps like Aphidius megourae, for instance, like to hunt other insects like aphids in the low light of the evening. Researchers found that the wasps actually benefited from just a small amount of light pollution, such as from a town just over the horizon. Since most humans would like to keep the plants that aphids like to eat for ourselves, this may seem like an upside to light pollution.

When light levels increased, however, the tables turned in the aphids’ favor. Brighter conditions made the wasps confused and distracted, making them incredibly ineffective hunters. This left the aphid populations unchecked, and exposed the wasps to risk of hunger and attack from other predators.

Spare some darkness for nocturnal species

Researchers worry that this relationship is just one of many possible problems faced by nocturnal insects around the world. More and more of the planet’s landmasses are being lit at night, and this is very likely stressing various ecosystems that sun-loving humans aren’t likely to notice until real problems develop. Insect populations are declining, which is quickly leading to issues with pollination and food sources of larger animals. As much as people prefer well-lit spaces, we should consider at least holding ourselves to the dim light of a nightlight if we want to help preserve these nighttime ecosystems.

Source: Night-time lighting changes how species interact by University of Exeter, Phys.org

On July 18th, 2018 we learned about

Study of spiderwebs finds how to stay sticky when a surface is wet

Don’t tell the kids, but they might need fewer band-aids in the near future. As exciting as getting a colorful adhesive bandage for a scrape or cut may be, getting a second bandage after a bath is even better, because you get more trucks or robots without the need for another injury. Because of the way glues interact with water, bath time has generally ensured that no bandage would survive a full day, but that may soon change if scientists can learn to reproduce some key properties of spider silk.

Sticking to water instead of a surface

The root of the problem with glues and paints on wet surfaces is interfacial water. This water gets between the adhesive and it’s intended target, then ruins any bonds that were in effect by essentially taking their place. In the case of a bandage, this means that the adhesive ends up bonding with the water that was next to the skin, instead of the skin itself.

Loose band-aids or peeling paint is one thing, but creatures like spiders really can’t tolerate having their webs come unstuck whenever things get humid. Since plenty of spiders manage to keep webs stuck to moist leaves with enough strength to catch struggling prey, researchers started looking at the exact chemistry to see what their secret was. Their search eventually came to focus on three types of ingredients— two glycoproteins, a batch of low molecular mass organic and inorganic compounds (LMMCs) and interestingly, water itself.

Working with water instead of against it

On their own, each of these ingredients wasn’t anything terribly unique. Glycoproteins are used as a source of stickiness by a variety of organisms, from algae to sea stars to ivy. The trick was how each ingredient complimented the others. Researchers found that the LMMCs worked to make the glycoproteins stick better, mainly by absorbing water and moving it away from the target surface. So rather than become completely hydrophobic and try avoid water at all costs, spider silk stays sticky by absorbing water and just moving it away from points of contact with other surfaces. With further development, researchers hope to apply this lesson to the design of adhesives we depend on, even if it means that a water proof band-aid will actually need to be water-absorbent.

Source: Research on spider glue resolves sticky problem by Lisa Craig, Phys.org

On July 8th, 2018 we learned about

The sugar content of plants signals brown planthoppers to specialize in flight instead of reproduction

As a human, I know that eating extra sugar in my diet will generally only help me produce extra fat on my body. There’d be some neurological pleasure associated with eating the sugar, but once I covered my caloric needs for the day, I wouldn’t gain anything more interesting than a bit of pudge around my waistline. As unglamorous as that is, it’s even worse when you compare it to what brown planthoppers (Nilaparvata lugens) do with their extra sweets— instead of getting fat, these small insects turn their extra sugar into longer wings, allowing them to travel to new homes when their plant of origin has been depleted.

Soaring when things get sweet

Strictly speaking, it’s not that the planthoppers need sugar to grow wings, but that the sugar is a signal that it’s time to migrate to a new plant. Unlike humans and other mammals, the planthoppers aren’t actually terribly interested in consuming sugary glucose from the rice plants they live on, as they’d rather chow down on amino acids. As a rice plant ages, it produces fewer of the planthoppers’ favorite proteins and more glucose, which the insects apparently use a signal that it’s time to move on to a new edible home.

That migration isn’t easy though, and only a subset of planthoppers will ever be capable of moving on. This is because planthoppers can grow into one of two body types by the time they reach adulthood; they can either have stubby wings but large, productive ovaries or they can have longer, flight-suitable wings and smaller ovaries. Researchers only recently confirmed that the insects’ glucose consumption was the key factor in which body type was each bug ended up with. In fact, planthopper anatomy is so tightly controlled by glucose that injecting the young insects with glucose could get them to grow larger wings, even if they were raised in a lab without rice plants at all.

Wings at the wrong time?

Of course, none of this was being investigated to help the planthoppers. The insects are considered pests, as they consume large amounts of rice needed for human consumption, and so the hope is that understanding exactly how they mature into a winged form will help people devise a way to control their proliferation. Since a planthopper can’t reverse its growth once it’s started down one path or the other, researchers are looking for a way to use the bugs’ specialization against them. If they could be exposed to extra glucose, for instance, they might be spurred to migrate and reproduce less, sparing plants from being completely consumed. Or if the glucose could somehow be repressed, they might end up staying on an older plant long after its amino acid supply had been depleted.

Source: Host plants tell insects when to grow longer wings and migrate, WSU Insider

On June 3rd, 2018 we learned about

Bumblebees’ difficulty parsing iridescent objects may explain other dazzling prey

The shiny, shifting hues of an iridescent peacock feather is usually pretty eye-catching. Thanks to nanometer-sized structures in the feathers’ surface, light is reflected at a variety of angles at once, giving the feather a seemingly dynamic range of bright colors. Beyond a peacock’s blue-green feathers, iridescence can be found in fish scales, sea shells, and minerals, but the flashy appearance in animals like birds may have confused our understanding of its utility. While we may find it enjoyable to look at, researchers are finding that bees, and likely all insects, have a hard time comprehending the silhouette of iridescent objects, suggesting that some of these bright, shiny materials may have actually evolved to help some creatures hide from predators.

Bewildered bumblebees

To investigate how insects see iridescence, researchers created artificial flowers in various shapes for bumblebees. Once the bees had learned which shape was likely to have the highest concentration of sugar water, the flowers were covered in iridescent materials to see if the bees could still locate the best food sources in these new conditions. Even though the silhouettes were the same, the bees had a lot more trouble finding their favorite-shaped ‘flower,’ indicating that the new color scheme made it hard for them to recognize the form of each object.

While bumblebees are not predatory themselves, their eyes are similar enough to other insects that researchers believe this has implications for visually-oriented insect predators. A beetle with a matte wing case might be easy to spot on a leaf, whereas the iridescent wing case of a rose chafer (Macrodactylus subspinosus) likely looks like a confusing jumble of shapes, making the beetle hard to identify from a distance. Of course, being able to hide from other insects may not be most bugs’ biggest concern, as birds are much more likely to pose a threat to the average beetle. If researchers can confirm that iridescent body parts also disrupts bird predation, it would demonstrate how looking flashy may have evolved for insect safety, although it might also raise questions about those peacock feathers that were presumably meant to be examined by other birds.

Camouflage based on confusion

This concept of dazzling camouflage was first coined over 100 years ago by Abbott Thayer. The artificial camouflage used by militaries today operate on a similar principal, as they aim to break up easily recognizable silhouettes of humans and vehicles just enough to make them harder to target. Zebra stripes are thought to function in a similar way, as a herd of black and white stripes shifting and moving may make it just a bit harder for a predator to target a single individual, buying the zebras a few precious seconds for escape. Since iridescence turns up in other places, such as minerals, there’s likely more uses for it than just camouflage, but dazzling predators like this would help explain how certain bugs “hide” in plain sight.

Source: Bumblebees confused by iridescent colors by University of Bristol, EurekAlert!

On May 23rd, 2018 we learned about

Two types of taste-buds allow bees to enjoy their nectar more than other insects

My daughter might be part honeybee. While her younger brother seems to think the best way to eat ice cream or candy is to gobble it up quickly, she figures the experience should be extended for as long as possible, even if that means licking a single Skittle for minutes at a time instead of just chewing it up in her mouth. Now, bees don’t necessarily ration our their enjoyment of nectar from flowers in quite this manner, but they do spend a lot more time than other insects slurping up the sugary liquid, eventually collecting more nectar and pollen as a result. While some of that nectar will need to be shared with their hive, the bees aren’t strictly being dutiful about their nectar collection— their mouths are actually adapted to help maximize their enjoyment of every sugary sip in a way my daughter would be envious of.

Like many foods that non-carnivores enjoy, the sugars in nectar activate specialized sensory cells on a bee’s proboscis, or mouth parts, which send a signal back to the brain. This usually coincides with a pleasurable release of neurotransmitters, providing positive feedback for acquiring some calorie-rich food. Over time, this response is diminished, presumably to make sure an animal doesn’t just burn out its taste buds by constantly soaking them in the first source of sugar it can find, which is why a tenth piece of candy might not feel as exciting to eat as the first.

Repeating the first sugary sip

Since bees are gathering nectar and pollen for more than their own consumption, evolution has set them up with an incentive to linger in flowers a bit longer than other insects. In addition to the sweet-sensitive taste receptors, they have secondary nerve cells that intermittently interrupt the process, causing the timer on their enjoyment to repeatedly reset. So by hitting restart on this process over and over, the bee is incentivized to suck up nectar for a longer period of time, maximizing each visit to a flower which can last as long as 10 seconds.

Aside from explaining what keeps bees on a particular flower for extended nectar-slurping sessions, this is also the first time scientists have ever seen taste-oriented nerve cells interact with each other, rather than simply pipe information straight to an animal’s brain.

Source: What gives bees their sweet tooth? by Newcastle University, Phys.org

On May 15th, 2018 we learned about

Kim the regal jumping spider surpasses robotic mimics’ movement by leaps and bounds

As every Mario player knows, if you want to make a short, low jump, you just tap the A button. To get across a larger gap, you need to combine a running start with holding the A button for a longer amount of time. It’s a simple enough system, and yet it’s somehow not good enough for engineers trying to build tiny jumping robots. Real world complications, like physics and efficiency, pushed them to draw inspiration from some of the world’s real masters of platforming-jumping spiders.

Regal jumping spiders (Phidippus regius) are quick, tiny arachnids that can launch themselves across relatively large gaps to find safety and hunt down prey. Spiders like a regal jumping spider actually move so quickly it’s hard to tell exactly what goes into their amazing leaps, some of which can span over five-times the spider’s body length. It’s been established that spider legs move with a mix of muscle strength and changing in body fluid pressures, but to find out more researchers needed to carefully record a spider’s movement in action.

Effort and efficiency

A single spider, named Kim, was recruited to demonstrate her athletic prowess in front of a set of high-speed cameras. Kim was repeatedly prompted to jump between two adjustable platforms, almost like a gentle, tiny obstacle course. Once researchers could really see how the spider moved, they saw that Kim clearly put some thought into each jump— longer jumps were made at the most efficient angle possible, maximizing distance while minimizing effort. Shorter leaps showed an emphasis on speed, as Kim would often move in a flatter arc that would minimize distance and flight time, even if it required more of a push with her back legs to get airborne. Oddly, they also found that Kim prepped for each jump by attaching a piece of silk to the platform she was jumping off of, although researchers aren’t sure how that helped her. The silk may help provide course-correction on longer jumps, or just act as a safety harness in case the spider misses its target.

The deployed silk and distance-sensitive movements present a few challenges for engineers who would like to replicate the spiders’ jumps. While they were able to build a device that could spring across a gap, researchers concede that building in sensors, processors and other machinery to control a leap may be difficult feat in a device the size of a fingernail. They hope that some gains can be made from further study of exact mechanics of the spider’s legs. While spiders like Kim certainly use hydraulic pressure to help flex their limbs, calculations suggest that their muscles alone would be able to handle the movement observed in this study. As such, the role of the fluid pressure in each leg remains unclear. Maybe it just provides extra strength to hold the B button?

Source: Scientists train spider to jump on demand to discover secrets of animal movement by University of Manchester, Science Daily

On May 1st, 2018 we learned about

Beyond growing eggs, mosquitoes drink blood to deal with dehydration

Call me crazy, but fresh blood doesn’t sound like a refreshing beverage. Sure, plasma is mostly water, but blood sucked from the source is going to be piping hot. Still, drinking blood is apparently an attractive notion to thirsty, female mosquitoes. This realization is a bit of a surprise, since females usually collect blood to grow their eggs, going as far as ejecting the water content of blood to make more room for nutritious protein in their stomach. Nobody thought these insects had any interest in sipping blood for other purposes, which helps explain how researchers stumbled upon the mosquitoes’ thirst by accident.

Using blood as a beverage

Mosquitoes were being transported through a lab, when a batch of slightly dehydrated females escaped from a vial. Researchers noticed that they were particularly aggressive in their attempts to bite the people in the lab, which didn’t match their expected behavior. Since mosquitoes lay their eggs in water, the assumption was that mosquitoes without access to water wouldn’t attempt to lay eggs, and thus not need protein from anyone’s blood. Why risk being swatted for a resource that wasn’t really needed?

A larger experiment was then launched to see if the dehydration was driving the mosquitoes’ aggression, rather than dampening it. When allowed to fly more freely with access to chicken blood in a simulated animal, dehydrated mosquitoes were found to be much thirstier than usual. As many as 30 percent of parched females made an effort to drink blood, versus the 5 to 10 percent of females that would usually stop for a sanguine snack. In line with the thirst hypothesis, higher temperatures seemed to drive the mosquitoes to drink more blood, apparently without any higher chances of reproduction.

Providing an answer to other questions

This behavior was surprise, but it actually helps explain otherwise confusing patterns in the spread of mosquito-borne pathogens like the Zika virus or malaria. Infection rates go up when mosquitoes are breeding, but they were also known to go up during droughts. This spike in blood-sucking now makes sense, since the mosquitoes were probably using people’s blood as a substitute for depleted water and nectar supplies. Knowing this may help in the planning of disease prevention, since we can now predict mosquito activity related to these dry weather conditions.

Source: Mosquitoes bite not just to lay eggs but also to quench their thirst during drought, study found by Michael Miller, Phys.org

On February 8th, 2018 we learned about

Ancient arachnid appears to be an amalgam of spiders and scorpions

Arachnids have apparently been experimenting with limbs for the last 400 million years. While modern arachnids’ eight legs may seem weird enough, what we live with today is relatively tame compared to what was scuttling around during the Mesozoic era. Specimens recovered from ancient amber have revealed other offshoots of the arachnid family tree, some of which are almost an amalgam of spiders and scorpions, complete with long, whip-like tails. There’s no evidence that those tails delivered venom, but it does give us a better sense of the wide spectrum of spidery creatures that left us with the arachnids we know today.

The latest specimen has been named Chimerachne yingi, as it’s body looks like it combines features from both spiders and scorpions. Like it’s modern kin, the “chimera spider” sported eight legs, as well as function, silk-producing spinnerets. These critical organs are actually highly specialized limbs, and weren’t present on older arachnid ancestors. Combined with an age of 100 million years, C. yingi is probably one of the closest relatives to modern spiders ever found, even though it’s not thought to be a direct ancestor of what lives today.

Defined by differences

This is where C. yingi’s differences become relevant. Its exoskeleton is structured more like a scorpion than a true spider, with segmented plates along its abdomen that would have made its rear end more flexible. Even more dramatically, C. yingi sported a tail longer than its tiny, 0.07-inch body. That tail was thin and probably fairly flexible, evolved from yet another limb structure. It probably didn’t get used like a scorpion’s tail though, as researchers suspect it acted more like a rear-mounted antenna, allowing arachnid to probe its surroundings. Like other specific behavior, this can’t be completely confirmed from the specimen trapped in amber, but the overall structure looks more like a sensory tool than any kind of weapon or leg.

In the end, C. yingi wasn’t technically a spider. It was classified as an uraraneid, which was an order of arachnids that likely diverged from the modern spider lineage hundreds of millions of years ago. Their common ancestor likely sported the signature limbs and spinnerets, possibly along with tails too. It’s thought that the arachnids that eventually became our modern spiders must have then lost their shared tail and solidified their abdomens, diverging from both the uraraneids and arachnids like scorpions. So while this tailed creature wasn’t a direct relative of today’s spiders, its unusual anatomy is still helping us understand how spiders evolved.

Source: Part spider, part scorpion creature captured in amber by Elizabeth Pennisi, Science

On January 31st, 2018 we learned about

Argentine ants’ advanced chemical weaponry may improve insecticides used against them

As countless action movies have taught us, one of the best tactics to defeat an unstoppable adversary is to use their strengths against them. When those adversaries are invasive Argentine ants, it’s hard to immediately throw their abilities back at them. For instance, it’s unlikely that we could convince one of a colony’s multiple queens to suddenly assassinate her sisters. Similarly, it’s not clear how we might convince neighboring Argentine ant colonies to suddenly become competitive with each other. However, the way these ants fight native species may finally be providing an opening, as the chemicals they use in an attack might soon be used against them.

Argentine ants (Linepithema humile) are smaller than many other ant species, but that doesn’t stop them from engaging in combat. When taking on something like a Californian harvester ant (Pogonomyrmex barbatus), the Argentine ants will engage in what’s known as gaster bending, wherein they dab their gaster, or abdomen, against their foe’s body. Upon contact, they secrete a mix of compounds, including dolichodial and iridomyrmecin, which have been confirmed to cause irritation and disorientation in the recipient. Even more importantly, these secretions attract other Argentine ants to the fight so that they can overwhelm the native ant in a larger attack. While researchers aren’t about to start dabbing Argentine ants with their own secretions, the fact that these compounds call in more ants may prove useful in the production of bait hydrogels.

Building better bait

Unlike the hapless harvester ants, humans have two ways to fight Argentine ants, both of which involve poisoning them. Insecticides can be sprayed in an area, and can be effective for a length of time on various surfaces. However, they can also end up leaching into water supplies and harming other animals. A more discrete option is then baiting, where a poison is mixed into an attractive substance, like sugar water, for the ants to eat and carry back to their colony. The poison is slow to take effect, allowing it to be shared with a greater number of ants before they start dying off. The best baits come in the form of hydrogels, which resemble small, gelatinous pellets, and remain potent for longer periods of time while requiring smaller doses of poison.

Naturally, bait only works if it’s attractive to the target. One way to heighten the allure of toxic hydrogel pellets is to add ant pheromones to the mix, which attracted more ants, and thus performed 32 percent better than “unscented” controls. That’s impressive on its one, but the secretions from battling Argentine ants may be even better. In addition to attracting more ants, the fact that the dolichodial and iridomyrmecin also irritates native species would help avoid accidental poisonings of the wrong ant. Even though the ants use these secretions to target their competition, it looks like it may do a great job of targeting Argentine ants as well.

The importance of the invasion

At this point, Argentine ants have spread to many parts of the world. The problem is that as an invasive species, none of their new ecosystems have any way to keep them in check. While they generally don’t attack each other, as Argentine ants drive out native species they essentially break the ecosystem- important duties that native species previously carried out, like pollination, don’t get done. The fact that Argentine ants also preserve pests like aphids in order to harvest their ‘honeydew’ makes them an even bigger problem, which is why there’s so much research looking for ways to control, or at least curb, their world domination.

My four-year-old said: I feel sad for the other ants.  I don’t like these ants! They’re bad… I guess they’re good for the aphids though, and ladybugs eat those.

Source: For global invasion, Argentine ants use chemical weapons by University of California - Riverside, Phys.org

On January 16th, 2018 we learned about

The wolf, pirate and pelican spiders that prey upon their eight-legged peers

Going by the numbers, it may spiders seem to have a particular vendetta against insects. After all, eating up to 800 million tons of bugs every year takes some dedication, or at least some well-honed predatory adaptations. As it turns out, eating only bugs would leave a lot of other food on the table, such as spiders themselves, and so some species have diversified their diets. As great as spiders are at catching crickets and ants, it turns out that they’re great at hunting their fellow arachnids as well.

Speedy stalkers

On the generalist side of things, wolf spiders will eat just about anything they can get a hold of— even small vertebrates. Instead of waiting in a web, spiders in the Lycosidae family travel along the ground or in burrows to hunt for prey while trying to avoid being eaten themselves. Some wolf spiders can be slightly strategic in how they hide and ambush their food, but for the most part they get by on speed and a bit of stealth.

Home invaders

Cellar spiders, often known as daddy long-legs, use more traditionally “spidery” tactics to catch their food. Their messy, tangled webs can catch a variety of insects, but they’ll also venture into other spiders’ webs to attack its original occupant. Their long, spindly legs help them move quickly over both their own and other spiders’ silk, giving them an edge when they feel like dining on arachnid.

Pelican impalers

Eriauchenius and Madagascarchaea spiders are a bit more specialized for picking off other spiders. Known more commonly as pelican spiders, these unusual predators have long “necks” and even longer chelicerae, the fang-tipped mouthparts that are much more modestly sized on other species. The combination of an elevated mouth and long chelicerae lets these spiders impale and hoist their prey off the ground like a hungry forklift, trapping prey in the air until they finally die. Specimens found in amber show that this lineage has been using this immobilizing strategy for at least 50 million years. They can be found in South Africa, Australia, and Madagascar, with the latter location being home to half the species alive today.

Pirate raiders

Pirate spiders in the family Mimetidae don’t have any special hook or peg-leg anatomy, as their names comes from the range of behaviors they use to acquire food. Rather than build their own webs, they search for other species’ webs to raid, usually starting with orb or cobweb weaver themselves. The pirate spider will first pluck at different threads in the web to imitate trapped prey in an attempt to lure the original spider into danger. Once in range, the pirate spider will lunge at its target, where a bite to the leg will immediately paralyze it’s meal thanks to the hunter’s spider-specific venom. Once the host spider is dispatched, the pirate may make use of the web to catch a few bugs as well, even eating other spiders’ eggs if it finds them.

This is by no means the complete list of spider-on-spider predation. For every specialized nest or venom, there’s probably another spider waiting for its next chance to eat some of its kin, assuming it doesn’t fill up on insects first.

Source: Who eats spiders? by Ben Goren, Spiderbytes