If you travelled back to Spain, during the Cretaceous period, you might see an insect so bizarre that you’d think you were hallucinating. That’s certainly what Ricardo Pérez-de la Fuente thought when he found the creature entombed in amber in 2008.
The fossilised insect of the larva of a lacewing. Around 1,200 species of lacewings still exist, and their larvae are voracious predators of aphids and other small bugs. They also attach bits of garbage to tangled bristles jutting from their backs, including plant fibres, bits of bark and leaf, algae and moss, snail shells, and even the corpses of their victims. Dressed as walking trash, the larvae camouflage themselves from predators like wasps or cannibalistic lacewings. And even if they are found, the coats of detritus act as physical shields.
We now know that this strategy is an ancient one, because the lacewing in De la Fuente’s amber nugget—which is 110 million years old—also used it. It’s barely a centimetre long, and has the same long legs, sickle-shaped jaws, and trash-carrying structures of modern lacewing larvae. But it took camouflage to even more elaborate extremes. Rather than simple bristles, it had a few dozen extremely long tubes, longer even than the larva’s own body. Each one has smaller trumpet-shaped fibres branching off from it, forming a large basket for carrying trash.
De la Fuente called it Hallucinochrysa diogenesi, a name that is both evocative and cheekily descriptive. The first part comes from the Latin “hallucinatus” and references “the bizarreness of the insect”. The second comes from Diogenes the Greek philosopher, whose name is associated with a disorder where people compulsively hoard trash.
In the forests of central Africa, there’s a plant that looks like it’s growing its own Christmas decorations. Shiny baubles sprout from between its leaves, shimmering in a vibrant metallic blue. Look closer, and other colours emerge – pinpricks of red, orange, green and violet. It looks as if Seurat, or some other pointillist painter, had turned their hand to sculpture.
But these spheres, of course, are no man-made creations. They’re fruit. They are the shiniest fruits in the world. Actually, they are the shiniest living materials in the world, full-stop.
They belong to a plant called Pollia condensata, a tropical metre-tall herb that sprouts its shiny berry-like fruits in clusters up to 40-strong. These little orbs are iridescent – they use special layers of cells, arranged just so, to reflect colours with extraordinary intensity. This trick relies on the microscopic physical structures of the cells, rather than on any chemical pigments. Indeed, the fruits have no blue pigment at all.
In the animal kingdom, such tricks are commonplace – you can see them at work on the wings of a butterfly, the shells of jewel beetles, or the feathers of pigeons, starlings, birds or paradise and even some dinosaurs. But in the plant world, pigments dominate and structural colours
were thought to be non-existent are much rarer.
None of our machines can do what a cuttlefish or octopus can do with its skin: change its pattern, colour, and texture to perfectly blend into its surroundings, in matter of milliseconds. Take a look at this classic video of an octopus revealing itself.
But Stephen Morin from Harvard University has been trying to duplicate this natural quick-change ability with a soft-bodied, colour-changing robot. For the moment, it comes nowhere near its natural counterparts – its camouflage is far from perfect, it is permanently tethered to cumbersome wires, and its changing colours have to be controlled by an operator. But it’s certainly a cool (and squishy) step in the right direction.
The camo-bot is an upgraded version of a soft-bodied machine that strode out of George Whitesides’ laboratory at Harvard University last year. That white, translucent machine ambled about on four legs, swapping hard motors and hydraulics for inflatable pockets of air. Now, Morin has fitted the robot’s back with a sheet of silicone containing a network of tiny tubes, each less than half a millimetre wide. By pumping coloured liquids through these “microfluidic” channels, he can change the robot’s colour in about 30 seconds.
Imagine trying to talk to two people at the same time. I don’t mean just talking to one and then the other – I mean simultaneously saying different things to both of them. And in one of those conversations, you’re pretending to be someone of the opposite sex. That’s exactly the exchange that Culum Brown from Macquarie University has witnessed off the east coast of Australia.
The speakers were mourning cuttlefish – relatives of octopus and squid, and masters of camouflage. By rapidly expanding and contracting sacs of pigment in their skin, cuttlefish can turn their entire bodies into living video displays. Colours appear and vanish. Mesmeric waves cascade across their flanks. They can even produce different patterns on the two halves of their bodies.
Brown saw a male cuttlefish swimming between a female and a rival male, and displaying different messages to both of them. On his left half, the one the female could see, he flashed zebra-stripe courtship colours to advertise his interest. But on his right half, facing the rival male, he flashed the mottled colours of a female. As far as the competitor was concerned, he was swimming next to two females, oblivious to the act of cross-dressing/seduction going on right next to him. The cheater, meanwhile, prospers.
Many animals defend themselves by mimicking something distasteful, like a wasp or a venomous snake. But the mimic octopus can don a multitude of disguises. It becomes a sea-snake by pushing six arms down a hole and waving the other two around in a sinuous wriggle. It turns into a flatfish by folding its arms back into a leaf shape and undulating them up and down. Its repertoire of venomous animals potentially includes lionfish, sea anemones, jellyfish, and more. It is one of the most dynamic mimics in the animal kingdom.
And now, the mimic has been mimicked.
Last July, while diving in Indonesian waters, Godehard Kopp saw a black-marble jawfish hanging around a mimic octopus. The little fish perfectly matched the octopus in both colour and pattern, blending in among the brown and white stripes of its arms.
There are two ways of becoming invisible: you can either be transparent so all light passes through your body, or you can blend in by taking on the colours of your surroundings. A truly incredible animal would be able to do both, switching between the two at a whim. And that’s exactly what some squids and octopuses can do.
Sarah Zylinski and Sonke Johnsen from Duke University found that two cephalopods – the octopus Japetella heathi and the squid Onychoteuthis banksii – can switch their camouflage strategy depending on how bright their environment is. When sunlight streams from above, they choose the see-through option. When their world darkens, they go for darker colours that blend in.
Male and female marsh harriers should be easy to tell apart: the males have grey wing-tips and tails, while the females are mostly brown with distinctive creamy heads. The males also tend to be around 30 percent smaller. But looks can be deceptive. In western France, many of the “female” harriers are actually cross-dressing males that permanently wear the plumage of the opposite sex. Audrey Sternalski has found that this unusual costume allows them to lead more peaceful lives.
Forty percent of male marsh harriers don female costumes, and they start wearing them from their second year of life. Their feathers have the same colours, and they’re smaller in size. Only their irises give them away – they are pale, rather than the ochre-brown of females or the yellow-white of males.
To test the effect of these colours, Sternalski created model harriers and placed them in the territories of real ones. He found that males attacked the male decoys twice as often as either the female or female-like ones. So, by looking like females, male harriers become the beneficiaries of a “non-aggression pact”. They can get access to resources and mates without incurring the wrath of other males. Indeed, Sternalski found that typical males were forced to nest twice as far from another male as the female-like males did.
Sternalski also found that the female-like males almost never attacked male decoys. Instead, they were more likely to attack other females (or female-like males), just as true females are. Not only did they look like females, they behaved like them too.
This raises several questions – are the female-like males simply doing a superficial impersonation, or are they “female” at a deeper physiological level? To find answers, Sternalski now plans to study the genetic basis of the harrier’s female mimicry.
The marsh harrier is one of only two birds whose males permanently don the colours of females. The other – the ostentatious ruff – also uses its disguise to avoid aggressive assaults. They sneak into the territories of more dominant males and surreptitiously mate with the resident females. Such strategies are fairly common in the animal kingdom – they’re found in ants, wasps, fish, and more. In most cases, the deceptive males get some sneaky sex, or avoid attacks from rivals.
But that’s not necessarily the case. In 1985, scientists discovered that some male red-sided garter snakes release a female pheromone that attracts big clusters of up to 17 amorous suitors. By luring these males to him, the female mimic more easily mates with an actual female. The goal seems obvious: distract other males. But the same group later showed that the female-mimics might simply benefit by drawing heat from the writhing balls of other duped males.
Reference: Sternalski, Mougeot & Bretagnolle. 2011. Adaptive significance of permanent female mimicry in a bird of prey. Biology Letters http://dx.doi.org/10.1098/rsbl.2011.0914
More on mimicry:
The lady’s slipper orchid (Cypripedium fargesii) does not look well. Its red and yellow flowers are nestled among two large leaves, both covered in unsightly black splotches. These look like the signs of a fungal infection, but they’re not. This orchid is deceptive, not diseased. It produces the black spots itself and in doing so, it lures in flat-footed flies that feed on fungus. The flies, duped by the orchid’s false spots, pick up pollen and spread it to another flower. By appearing infected, the orchid reproduces.
Late last year, I wrote about a bird called the rocket-tailed drongo and, in response to a comment, I noted the following:
“Drongos are notorious thieves and mimics. In South Africa, I spent a morning with a meerkat researcher, following live meerkats. He said that he had anecdotal evidence that the fork-tailed drongo would sometimes mimic the predator alarm calls of meerkats while they were foraging and then swoop down to nick their unearthed morsels.”
Well that evidence is no longer anecdotal. In a new study published today, Tom Flower from the University of Cambridge has indeed found that fork-trailed drongos can deceive meerkats into scurrying for cover by making false alarm calls. It’s the bird that cries hawk.
For most insects, walking onto a spider’s web and disturbing the sticky threads would be a very bad idea. The distinctive vibrations of wriggling prey only serve to draw the spider closer and inevitably ends in the insect getting bitten, wrapped in silk and digested. But this story doesn’t always unfold in the spider’s favour. Some vibrations aren’t made by helpless prey, but by an assassin lurking on the web.
The assassin bug (Stenolemus bituberus) is a spider-hunter. Sometimes, it simply sneaks up to spiders on their own webs before striking, plunging its dagger-like mouthparts into its prey. But it also has a subtler technique. Sitting on the web, it plucks the silken threads with its legs, mimicking the frequency of weakly struggling prey. These deceptive vibes are an irresistible draw to the spider, who rush towards their own demise. The bug effectively has a way of ordering for delivery when it doesn’t want to go out for a meal.