Brad Kelly, USDA Forest Service

Sticky Plants Protect Themselves with a Deadly 'Siren Song'

Brad Kelly, USDA Forest Service

In the forests of Northern California, a plant called Van Houtte’s columbine always draws a crowd. It’s a beautiful plant, though not quite as charismatic as a towering redwood or ancient bristlecone pine. But that’s fine, because its visitors aren’t people looking for photo ops, but hummingbirds and bees coming for nectar and pollen, and plenty of insects in search of a meal.

Some of these bugs are a problem for the plant, like the moth caterpillars that munch on its buds and flowers. Others are helpful, scavengers and predators like stilt bugs and assassin bugs that eat the caterpillars and other herbivores. And then there are the insects that show up to the plant seemingly for no reason at all. They don’t live on the columbine and don’t come to eat the plant or other insects, and all they get for their visit is a slow death. These visitors, or “tourists,” as entomologist Eric LoPresti calls them, come by only to get stuck and die in the fine, sticky “hairs” called trichomes that cover the plant. 

The plants are literal tourist traps, and LoPresti shows in a new study published recently in the journal Ecology that their victims don’t just show up and get caught by accident, but are lured in so that the columbines can attract all those predatory bugs that protect them from caterpillars. 

Quiet as they seem to us, many plants are chemical chatterboxes, communicating with each other and with insects through chemical signals. Some signals warn other plants of danger and prompt them to mount a defense. Others are used recruit helpful insects that act as bodyguards. LoPresti suspected that’s what the columbine might be doing, but in a more roundabout way. Instead of calling directly to predators for help, he thought, they lure innocent tourists to their deaths with a chemical “siren song” and then use their bodies as bait to entice predators to hang around.


To test that idea, LoPresti ran two experiments at a nature reserve where Van Houtte’s columbine is plentiful. First, he and his team wanted to see whether the dead tourist bugs did what they thought they did and attracted predators that helped the plants. Last July, they found an isolated group of columbines in a forest and pulled all of the dead bugs off of half of them every few days. The other half they left alone, letting them collect hundreds to thousands of tourist corpses. They did this for three months, keeping track of the number of trapped tourists, predators and caterpillar-damaged parts on each plant as they went along. 

They also tested whether the tourists just had bad luck and showed up on their own or if they columbine was really luring them. In a meadow where the columbines grow, they clipped some leaves and other pieces from the plants and put them in petri dishes covered in a plastic mesh. They laid these petri dishes out along the side of the meadow, alternating them with empty ones. A day later, they returned to see how many bugs got caught in the mesh.  

With both of their predictions, LoPresti and his team were right. In the forest, the plants with the trapped bugs on them had 74 percent more assassin bugs and other predators crawling on them than the ones that had their tourists removed. These bugs ate the caterpillars or scared them off, and the plants that hosted them had much less damage to their parts than the tourist-free ones. Meanwhile, the petri dishes that had columbine bits in them had 21 percent more bugs trapped in their mesh than the empty controls. Because the mesh hid the plant parts from view, LoPresti says, the attraction is very likely due to volatile chemicals the plants release. 

The researchers say their results demonstrate a “‘siren song’ indirect defense” that relies on drawing tourists that then draw predators. While direct attraction of bodyguards is a common plant defense, the team writes, a plant using a middleman like this is a first. 

LoPresti thinks that other plants could be using the same defense as Van Houtte’s columbine, but haven’t been reported by scientists. Looking through other studies, they identified sticky insect-trapping plants in 49 different plant families, most of them non-carnivores that wouldn’t benefit directly from attracting bugs and being covered in their corpses. The researchers want to do similar experiments with some of these other plants to see if they’re also defending themselves indirectly by inviting tourists to hang around, but never letting them leave alive. 

These Fake Flowers Could Help Scientists Study At-Risk Bees

If you haven't heard, the world's bees are having a crisis. According to one recent study, bee populations in some areas have plummeted by 75 percent in a quarter of a century. Some countries have introduced legislation banning certain pesticides in response to the news, but solving the complicated problem will likely require much more research. In order to gather better data on bee behavior, one new media artist has developed a machine that can give scientists a bug's-eye view.

As Co.Design reports, Michael Candy's Synthetic Pollenizer is designed to blend into a bee's natural environment. Yellow circles bolted around the opening of the device imitate the petals on a flower. Tubes pump real nectar and pollen into the center of the fake flower, so when bees land on it to feed, they're collecting real reproductive materials they can spread to the next plant they visit.

Candy, who's based in Brisbane, Australia, originally conceived the apparatus as a way for scientists to track the pollinating behaviors of bees. The synthetic flower is outfitted with cameras and dyes, and with enough of them distributed in the wild, researchers could see which bees travel to certain places and how long they stay.

After his concept reached the final round of the Bio Art and Design awards in the Netherlands, Candy decided to create his own prototype with help from an urban beekeeper in Melbourne, Australia. The invention worked: Bees mistook it for real flora and carried pollen from it to their next destination. But to use it for tracking and studying bees on a larger scale, Candy would need to build a lot more of them. The pollinators would also need to be scattered throughout the bees' natural habitats, and since they would each come equipped with a camera, privacy (for nearby residents, not the bees) could become a concern.

Even if the concept never gets the funding it needs to expand, Candy says it could still be used in smaller applications. Fake flowers designed to look like real orchids, for example, could encourage the pollination of endangered orchid species. But for people studying dwindling bee populations, orchids are low on the list of concerns: 30 percent of all the world's crops are pollinated by bees [PDF].

[h/t Co.Design]

A Chemical in Bed Bug Poop Might Be Making You Feel Sick

Bed bugs can give you nasty bites and a lifetime of nightmares, but scientists have long wondered if the creepy parasites can pass diseases to their hosts. For years, the general consensus was no: Unlike ticks, mosquitos, and other insects that are known to feast on human blood, bed bugs aren't packing any harmful pathogens in their bites. Yet according to a new study, spotted by Gizmodo, the bugs don't need to nibble on us to make us sick. Histamines in their poop might be aggravating our immune systems.

For their study, recently published in the journal PLOS One, scientists at North Carolina State University tested the dust in a bed bug-infested apartment complex. They found that samples from some infested homes had histamine levels 20 times higher than those without bed bugs. This was still the case three months after the buildings had been treated by exterminators.

Histamine is a chemical compound produced by our bodies. In small amounts, it works as a vital part of our immune system. It's activated in the presence of allergens, irritants, and pathogens. Say a puff of dust goes up your nose: Histamine is what prompts your body to sneeze it out. It's also the culprit behind the watery eyes, runny nose, and itchy skin you might experience during an allergy attack (which is why you might take an antihistamine to calm these symptoms).

But we're not alone in our ability to produce histamine. Recent research has shown that the chemical is present in bed bug feces. When the insects poop, they spray histamines into the same air that homeowners breathe. A few whiffs of the stuff is likely nothing to worry about, but scientists are concerned about the effects environmental histamine can have on people over an extended period of time. The chemical compound can cause allergic reactions on its own and possibly make us more vulnerable to existing allergens. The implications are especially serious for people with asthma.

"Dermal, nasal, or respiratory responses (e.g. bronchial reactivity) to histamine in clinical tests suggest that exposure to histamine in the environment would constitute a significant health risk, although information on environmental exposure is limited," the study authors write.

For now, scientists can do nothing but speculate on what these results might mean for public health. Humans are prepared to treat only histamine that's produced by our own bodies, and dealing with the effects on histamine spread by bed bugs is uncharted territory for doctors and scientists. How exactly bed bugs obtain the chemicals in the first place is also unclear, but researchers suspect that it's a combination of the blood they suck from us and histamine they make on their own as a type of pheromone, indicating to other bed bugs that a place is safe to invade.

Following this study, the North Carolina State scientists plan to conduct more intensive research on the impact histamine produced by bed bugs is having on the people who live with it. While the best way to eradicate histamine in bed bug poop is still a mystery, there are plenty of ways to deal with the bugs themselves if you suspect you have an infestation.

[h/t Gizmodo]


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