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Dozens of Insect Species Living Only On Two Types of Flower

Los Amigos Biological Station sits within the Peruvian Amazon—one of the planet’s richest hotspots for life. Countless species fly, scurry, climb and burrow through the surrounding rainforest. To be at the station is to be surrounded by life at its most diverse and wondrous.

But you don’t have to go into the forest to find diversity.

The research station has a kilometre-long airstrip, and its borders are thick with climbing squash vines descending from the trees. A team of scientists led by Marty Condon from Cornell College collected some 3,600 flowers from these vines, all belonging to just two species. They found entire worlds.

The flowers were home to 14 species of fly, which lived nowhere else. “When we go out in the field, we collect every flower, fruit and stem of this group. These particular flies have only come out of these two plants,” says Condon. Most were even restricted to either the male or female flowers of their chosen plant.

There was more. Condon also found 18 species of parasitic wasps, which attack the fly larvae and lay eggs inside their bodies. Two of the wasps were generalists that attacked a wide variety of hosts. But the vast majority were specialists that targeted just one of the 14 available fly species, even though there were several possible targets around.

It’s difficult for us humans to appreciate just how restricted and specialised creatures like this can be. We are a global species. When you can travel to the other side of the planet in less than a day, it’s hard to imagine how dozens of species can exist nowhere else but on a single type of flower.

Most of these species all looked the same. Condon’s team used their DNA to tell them apart. Specifically, they sequenced a gene called COI in all of the flies. Your version of COI is a 98 percent match for a chimp’s, but none of the fly species from the squash flowers shared more than 96 percent of their COI sequences. “A 4 percent different is huge,” says Condon. Once the DNA had split the lookalike flies into different groups, it became easier to find more visible differences between them, from subtle physical traits to distinctive mating rituals. “These flies really are extraordinarily different.”

Of course, with over a million known insect species, and many millions more left to discover, we expect insects to be diverse. Even so, Condon was astonished by what she found. If two flies exploit exactly the same resource, you’d expect the more efficient competitor to eventually oust its rival. In this way, species partition themselves into distinct niches—each one specialised to a certain area, or food source, or time of day. They can co-exist because they each do their own thing.

“That’s the standard scenario: there should be one thing on each kind of resource,” says Condon. “But when we got our samples in, we thought: Whoa, this is not like that at all. We found multiple insects feeding on exactly the same tissues of exactly the same species.” For example, the male flowers of Gurania spinulosa are home to 9 of the flies and 12 of the wasps. “That was totally unexpected,” says Condon. This town ain’t big enough for two, let alone nine or twelve.

Why so much diversity? The team found a big clue when they dissected almost 400 fly pupae. They found that many wasps actually do lay eggs in the larvae of several fly species—it’s just that the wasp larvae can only survive in the right host. If they get implanted into the wrong one, they’re dead. The host kills them, perhaps by mounting some sort of immune defence.

That explains why there are so many wasps on the two flowers: the majority of them are adapted to parasitise a single fly species, and the others are inhospitable.

But why are so many species of flies? Condon’s hunch is that this group of flies is ancient and widespread. They have been feeding on the same sorts of flowers throughout South and Central America for around 6 million years. That period saw the rise of the Andes, and regular waves of drought and rain. These changing conditions would have regularly fragmented the local plant populations, and the flies could have adapted to these isolated pockets. “Then previously isolated plant habitats come back together and bingo, there are multiple fly species on same host plants,” says Condon.

Alternatively, the flies could be diversifying because of the wasps. Each adapts into an “enemy-free space”, becoming impervious to the existing wasps. The wasps counter-adapt, so that both parasites and hosts foster extra diversity in each other. They’re caught up in an evolutionary game of cat and mouse (or wasp and fly), diversifying into new forms as they play. As Andrew Forbes, who was involved in this study, has previously show, diversity can create itself.

It’s a fascinating study. Different species can be separated by physical barriers like mountains or by rivers, or because they’re active at different times of the day, or even because they harbour different gut microbes. But in this case, it seems that the tangled interactions between parasites and hosts create the barriers that keep species apart, and set up entire webs of life on single flowers.

That’s the basic idea, but there’s a lot still to discover about these insects. For example, how do the flies kill the wasps? And how do the generalist wasps manage to target so many different flies with impunity. And why would the specialist wasps ever occasionally lay eggs on the wrong fly? The team found that they only ever did this on plants that also contained the right host. So, Condon believes that the wasps are tracking down their hosts with some sort of chemical cue, but once they’re in the right ballpark, they sometimes get confused. “They think, ‘It looks like I can put my babies here somewhere’, and they make mistakes,” she says.

“I think it’s pretty outrageous how much diversity could be out there,” says Condon. If just two flowers could play host to so many species of insect, just think about how many more are lurking on or in the other plants of the rainforest. How many are there, and how would we ever find them all?

Reference: Condon, Scheffer, Lewis, Wharton, Adam & Forbes. 2014. Lethal Interactions Between Parasites and Prey Increase Niche Diversity in a Tropical Community. Science http://dx.doi.org/10.1126/science.1245007

More on speciation:

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Ants disinfect their young by drooling backside poison

Personal hygiene is paramount for insects, as it is for us. They too must contend with a cavalcade of bacteria and fungi that threaten to soil their food and infect their bodies. And cleanliness is one of their most important defences against such infections. This goal is familiar to us, but the methods are… unorthodox.

Take the emerald cockroach wasp. Its larva disinfects its food, which happens to be is a zombie cockroach that the young wasp is devouring from the inside out. Its cleaning technique involves slobbering antibacterial fluids inside its living cradle-cum-larder. I’ve written more about the wasp’s behaviour at Nature News (including the see-through windows that scientists installed in cockroaches so they could watch the larva). Carl Zimmer also has you covered here at Phenomena.

For now, I’m going to deal with another recently discovered case of insect hygiene, involving ants that suck poison from their backsides and drool over their brood.

Ants, bees and other social insects live in dense colonies that could easily be wiped out by a single outbreak of disease. To prevent this from happening, the entire colony often acts as a giant immune system that works together to protect their health. Bees, for example, will sometimes buzz in tandem to raise their body temperature, creating a “social fever” that heats bacteria to death. Ants will groom each other to remove the spores of parasitic fungi.

Sylvia Cremer from the Institute of Science and Technology in Austria has spent years studying these hygienic behaviours, and she has found a new one in the garden ant Lasius neglectus. These ants are known to lick fungal spores off their larvae, which they store in pockets in their mouths. Later, they spit these out in small pellets. Now, Cremer has found that the ants have another trick: They slather a poisonous fluid over their denuded youngsters, turning their mouths into temporary “chemical disinfection chambers.’’

Cremer’s team members Simon Tragust and Barbara Mitteregger noticed that the ants don’t manage to clean every spore from their larvae. But even those they miss are much less likely to germinate. The secret to this suppression lies in the ants’ back ends, and specifically in a hole called the acidopore. If the team plugged this opening, the ants were only half as good at suppressing the growth of fungal spores.

The acidopore connects to an ant’s anus, pheromone gland, and poison gland. It’s that last one that matters. When Tragust ad Mitteregger gently poked the ants from behind, they would release their poison as a droplet. Depleted of this chemical supply, they lost their antifungal powers.

The droplet that comes out of the acidopore contains 37 chemicals, but mostly formic acid—a pungent substance that many ants use to defend themselves from predators. Formic acid even gets its name from ‘formica’, the Latin word for ‘ant’. It makes up 60 percent of the acidopore droplets, and accounts for 70 percent of its fungus-busting powers. The other substances, such as vinegary acetic acid, did very little on their own but gave an extra boost to formic acid’s antifungal properties.

Some of the ants would spray the poisonous cocktail directly onto the larvae, but most of them took an indirect route. They ‘licked’ their acidopore and sucked up their own poison into their mouths. They then cleaned their brood, and slathered the acidic poison over them in the process.

This method has many benefits. Tragust and Mitteregger think that it allows the ants to apply their precious chemicals more accurately and evenly. It also means that they disinfect their own mouths, since the acid kills the spores that they lick off the larvae, and stops any pellets they spit out from germinating.

The garden ant and the cockroach wasp are just two new examples of insects acting as their own pharmacists—using self-made chemicals to defend themselves against bacteria. In the simplest strategies, they groom themselves with defensive chemicals. Ants and termites do this, as do rove beetles groom themselves, which use a substance called stenusine to walk on water as well as repel fungi and bacteria.

Some species use their chemicals to clean their homes, relatives, or food supply. Some bees and wasps incorporate their venom into the building materials for their nests. Fire ants apply antibacterial chemicals onto their eggs, and liberally spray the stuff into the brood chambers, where the eggs are kept. The European beewolf—a  type of parasitic wasp—embalms the honeybees that it provisions for its larvae, by covering them with an oily secretion that stops water from condensing and makes it harder for fungi to grow.

At a time when many human societies lack decent sanitation, and others have only enjoyed it for a few centuries, it’s sobering to remember that insects have been practicing careful hygiene for millions of years.

Reference: Tragust, Mitteregger, Barone, Konrad, Ugelvig & Cremer. 2012. Ants Disinfect Fungus-Exposed Brood by Oral Uptake and Spread of Their Poison. Current Biology http://dx.doi.org/10.1016/j.cub.2012.11.034

Herzner, Schelcht, Dollhofer, Parzefall, Harran, Kreuzen, Pilsl & Ruther. 2013. Larvae of the parasitoid wasp Ampulex compressa sanitize their host, the American cockroach, with a blend of antimicrobials. http://dx.doi.org/10.1073/pnas.1213384110

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Wasps that lay eggs in wasps that lay eggs in caterpillars

(Left by Nina Fatouros, centre by Hans Smid, right by Harald Süpfle)

A very hungry caterpillar munches on a cabbage leaf and sets off an alarm. The plant releases chemicals into the air, signalling that it is under attack. This alarm is intercepted by a wasp, which stings the caterpillar and implants it with eggs. When they hatch, the larval wasps devour their host from the inside, eventually bursting out to spin cocoons and transform into adults. The cabbage (and those around it) are saved, and the wasp—known as a parasitoid because of its fatal body-snatching habits—raises the next generation.

But that’s not the whole story.

Some parasitic wasps are “hyperparasitoids”—they target other parasitoid wasps. And they also track the cabbage’s alarm chemicals, so they can find infected caterpillars. When they do, they lay their eggs on any wasp grubs or pupae that they find. Their young devour the young of the other would-be parasites, in a tiered stack of body-snatching. It’s like a cross between the films Alien and Inception.


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The enemy of my prey’s enemy is my friend, or Why parasitic wasps need each other

A.ervi attacks a pea aphid, by Alexander Wild

In a British lab, a wasp has become (locally) extinct. And then, another wasp follows it into oblivion. That’s odd because these two insects are not competitors. They don’t attack one another, and they don’t even eat the same food. They do, however, remind us that it’s very hard to predict how the decline of one species will affect those around it.

Some consequences are obvious. If an animal goes extinct, its loss will cascade up and down the food web, so that its predators will suffer but its prey will probably thrive. But food webs are webs for a reason, rather than a set of isolated linear “food chains”. Consequences can ripple across, as well as up and down.


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You can thank wasps for your bread, beer and wine

If wasps didn’t exist, picnics would be a lot more fun. But the next time you find yourself trying to dodge a flying, jam-seeking harpoon, think about this: without wasps, many of your ingredients might not exist at all. Irene Stefanini and Leonardo Dapporto from the University of Florence have found that the guts of wasps provide a safe winter refuge for yeast – specifically Saccharomyces cerevisiae, the fungus we use to make wine, beer and bread. And without those, picnics would be a lot less fun.

S.cerevisiase has been our companion for at least 9,000 years, not just as a tool of baking and brewing, but as a doyen of modern genetics. It has helped us to make tremendous scientific progress and drink ourselves into stupors, possibly at the same time. But despite its significance, we know very little about where the yeast came from, or how it lives in the wild.

The wild strains do grow on grapes and berries, but only found on ripe fruits rather than pristine ones. And they’re usually only found in warm summery conditions. So, where do they go in the intervening months, and how do they move around? They certainly can’t go airborne, so something must be carrying them.

Stefanini and Dapporto thought that wasps were good candidates. They’re active through the summer, when they often eat grapes. Fertilised females hibernate through the winter and start fresh colonies in the spring, feeding their new larvae with regurgitated food. In the digestive tracts of wasps, yeasts could get a ride from grape to grape, from one wasp generation to the next, and from autumn to spring.


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Mind-controlling virus forces parasitic wasp to put all its eggs in one basket

Leptopilina boulardi by Alexander Wild

In a French meadow, a creature that specialises in corrupting the bodies of other animals is getting a taste of its own medicine.

Leptopilina boulardi is a wasp that lays its eggs in fly maggots. When the wasp grub hatches, it devours its host form the inside out, eventually bursting out of its dead husk. A maggot can only support a single grub, and if two eggs end up in the same host, the grubs will compete with one another until only one survives. As such, the wasps ensure that they implant each target with just one egg. And if they find a maggot that has already been parasitized by another L.boulardi, they usually stay away.

Usually, but not always.

L.boulardi is sometimes infected by a virus called LbFV, which stands for L.boulardi filamentous virus. And just as the wasp takes over the body of its maggot target, so the virus commandeers the body of the wasp. It changes her behaviour so that she no longer cares if a maggot is already occupied. She will implant her eggs, even if her target has an existing tenant. After infected wasps are finished, a poor maggot might have up to eleven eggs inside it.


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Parasitic wasps vaccinate aphids by spreading anti-wasp bacteria

A black bean aphid is about to have a rough day. It has been targeted by a parasitic wasp, which lays several eggs inside its body. When the eggs hatch, the wasp grubs will try to eat the aphid from the inside out. If they succeed, the aphid will die, and the young wasps will burst from its corpse to find aphids of their own.

But the aphid isn’t necessarily doomed. There’s a chance that it will resist the attempt to usurp its body. If it does, the wasps will have done it a favour. When the mother wasp implanted its eggs, it also infected the aphid with bacteria that protect against parasitic wasps. It inadvertently vaccinated the aphid against its own kind.


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Flies drink alcohol to medicate themselves against wasp infections

Some people drink alcohol to drown their sorrows. So does the fruit fly Drosophila melanogaster, but its sorrows aren’t teary rejections or lost jobs. It drinks to kill wasps that have hatched inside its body, and would otherwise eat it alive. It uses alcohol as a cure for body-snatchers.

D.melanogaster lives in a boozy world. It eats yeasts that grow on rotting fruit, which can contain up to 6 per cent alcohol. Being constantly drunk isn’t a good idea for a wild animal, and the flies have evolved a certain degree of resistance to alcohol. But Neil Milan from Emory University has found that alcohol isn’t just something that the insect tolerates. It’s also fly medicine.


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Sociable wasps have an eye for faces

At first glance, we might think that all wasps look the same. But if you look closer at the face of a paper wasp Polistes fuscatus, you’ll see a variety of distinctive markings. Each face has its own characteristic splashes of red, black, ochre and yellow, and it’s reasonably easy to tell individuals apart. And that’s exactly what the wasps can do.

Michael Sheehan and Elizabeth Tibbetts have shown that these sociable insects have evolved the special ability to recognise each others’ faces. They can learn the difference between different faces more quickly than between other images, or between faces whose features have been rearranged. It’s an adaptation to a social life, and one that a close but solitary relative – Polistes metricus – does not share.


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How tiny wasps cope with being smaller than amoebas

Thrips are tiny insects, typically just a millimetre in length. Some are barely half that size. If that’s how big the adults are, imagine how small a thrips’ egg must be. Now, consider that there are insects that lay their eggs inside the egg of a thrips.

That’s one of them in the image above – the wasp, Megaphragma mymaripenne. It’s pictured next to a Paramecium and an amoeba at the same scale. Even though both these creatures are made up of a single cell, the wasp – complete with eyes, brain, wings, muscles, guts and genitals – is actually smaller. At just 200 micrometres (a fifth of a millimetre), this wasp is the third smallest insect alive* and a miracle of miniaturisation.


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Sex increases risk of being paralysed, buried, eaten alive (for locusts)

You know how it is: one minute you’re having sex and the next, your partner has been stung and paralysed, and you’re being dragged off to a burrow by your genitals only to be buried and eaten alive.

Such is the life of the Australian plague locust, a common pest that is targeted by the black digger wasp. The wasp is a parasite that creates living larders for her grubs. She stocks them with the bodies of paralysed insects. Last December, the locusts formed dense plagues in southeastern Australia just as the wasps were starting to collect fresh meat for their young. And Darrell Kemp from Macquarie University was watching as the two species collided.


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Beetles turn eggs into shields to protect their young from body-snatchers

Some parents give their children a head start in life by lavishing them with money or opportunities. The mother seed beetle (Mimosestes amicus) does so by providing her children with shields to defend them from body-snatchers.

A female seed beetle abandons her eggs after laying them. Until they hatch, they are vulnerable to body-snatching parasites, like the wasp Uscana semifumipennis. It specialises on seed beetle eggs and lays its own eggs inside. Once the wasp grub hatches, it devours its host. The wasp problem is so severe that around 70 percent of the beetles’ eggs can be infested.

But the mother seed beetles have a defence, and it is a unique one. Joseph Deas and Molly Hunter from the University of Arizona have found that they can protect an egg from this grisly fate by laying another one on top. Sometimes, the mothers lay entire stacks of two or three eggs. The tops ones are always flat and unviable. They never hatch into grubs and they completely cover the ones underneath.


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Wasps, ladybirds and the perils of hiring zombie bodyguards

Hiring zombie bodyguards to look after your children can have its drawbacks. They might end up with fewer children of their own.

The wasp Dinocampus coccinellae is a body-snatcher, or perhaps a “bodyguard-snatcher”. She’s on the hunt for a spotted ladybird. When she finds one, she stings it and lays an egg inside its body. Her grub hatches and starts eating the ladybird alive. Around three weeks later, it bursts out of its host.

But the ladybird doesn’t die. The grub hasn’t consumed all of its internal organs, and it leaves the ladybird partially paralysed but very much alive. Once out, it spins a silken cocoon between the ladybird’s legs and over the next week, it slowly transforms into an adult. Meanwhile, the ladybird stands guard over its own parasite. Its warning colours of red and black should deter would-be predators, and it twitches erratically if threats draw near. Its tour of duty only ends when the adult wasp eventually emerges from the cocoon and flies away.


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Pocket Science – wasps airlift ants away from food

It’s not a very fair fight. In one corner is a tiny ant. In the other is a large wasp, two hundred times heavier and capable of flying. If the two of them compete for the same piece of food, there ought to be no contest. But sometimes the wasp doesn’t even give the ant the honour of stepping into the ring. It picks up the smaller insect in its jaws, flies it to a distant site and drops it from a height, dazed but unharmed.

Julien Grangier and Philip Lester observed these ignominious defeats by pitting native New Zealand ants (Prolasius advenus) against the common wasp (Vespula vulgaris). The insects competed over open cans of tuna while the scientists filmed them.

Their videos revealed that ants would sometimes aggressively defend their food by rushing, biting and spraying them with acid. But typically, they were docile and tolerated the competing wasp. Generally, the wasp was similarly passive but on occasion, it picked up the offending ant and dropped it several centimetres away. In human terms, this would be like being catapulted half the length of a football field.

The wasps never tried to eat the ants, and they never left with one in their jaws. They just wanted them out of the picture. Indeed, the more ants on the food, the further away the wasps dropped them. This may seem like an odd strategy but at least half of the dropped ants never returned to the food. Perhaps they were physically disoriented from their impromptu flight, or perhaps they had lost the chemical trail. Either way, the wasps could feed with fewer chances of taking a faceful of acid.

Reference: Grangier and Lester. 2011. A novel interference behaviour: invasive wasps remove ants from resources and drop them from a height. Biology Letters http://dx.doi.org/10.1098/rsbl.2011.0165

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Wasps and flies have hidden rainbows in their wings

The wing of a fruit fly, viewed against a white background, looks very ordinary. It is transparent, with no obvious colours except for some small brownish spots. But looks can be deceptive. If you put the wing in front of a black background, it suddenly explodes in a kaleidoscope of colour. Oranges, blues, greens, violets – virtually the entire rainbow dances across the wing, except for red.

A French scientist called Claude Charles Goureau first noticed these vivid hues back in 1843. Since then, they have languished in obscurity, “apparently unnoticed by contemporary biologists”. Whenever new species of wasps or flies are described, their discoverers almost never mention the coloured patterns of the wings. The visible pigments have even been described as “evolution in black and white”. It’s like walking through an art gallery with a blindfold.

Now, Ekaterina Shevtsova from Lund University has taken off the blind. By photographing several species against dark backgrounds, she has revealed a world of hidden colour, rivalling that of more obviously beautiful insects. “The claim that fly and wasp wing patterns are no match for the incredible diversity of colourful butterfly wing patterns is obsolete,” she says.