Wasps are the main pollinators for the 750 species of fig worldwide, but some non-pollinating fig wasps also live in the fig fruit as parasites. For these parasites inside their fig world, female mates are so scarce that males violently fight among themselves to get them.

Theoretically, they should only attack other males of the same species – their competition. However, some fig wasps fight males from any similar-looking wasp species, says of the University of Reading in the UK and Western Sydney University in Australia. And the cost of engaging the wrong opponent can be grave. “We do find severed heads quite often,” says Cook.

Intrigued by the severed heads, Cook’s team investigated three Sycoscapter fig-wasp species in Australia. They picked the figs just as the wasps were becoming active and looked inside to assess the battleground.

They found that most fights were between males of the same species. However, brothers rarely fought each other because female wasps tend to only lay one male egg per fig, leaving a solo king to rule each fruity world.

But with many mother wasps doing the same, and unrelated species of wasp also laying eggs inside the same figs, the place gets crowded, with up to 100 wasps of all species within a fig.

Fighting blind

Surprisingly, a significant proportion of fights were between males of different species, which would not have been competing for mates.

The heavily armoured wasps use their massive jaws to bite and grapple with each other, tearing off legs, antennae and even heads. The wasps are a few millimetres long and built for battle, with no wings, thick exoskeleton armour and spikes on their bodies.

One explanation for the indiscriminate fighting is that the wasps cannot recognise their opponents.

Or it could just be beneficial to strike first. The wasps are crawling inside a 2-centimetre-long fig fruit, filled with hundreds of flowers and hardly any light. In that situation, it is hard to properly judge your enemy, and while you’re measuring them up, they may have already killed you, says Cook.

Fighting to the death is not normal behaviour in the animal kingdom. But the male parasitic fig wasps only live for a day or two as adults, never leaving the confines of the fig, so “although they’re risking their life, the future value of their life is actually quite small”, says Cook. And with only around three females of their species wandering inside each fig fruit, each opportunity to mate could be the last.

This fulfils the predictions of resource competition theory, which state that when there is intense competition for valuable resources, with no second chances, then it is worth risking your life, says Cook. “If your future prospects are really dismal then it’s worth risking a lot on the current opportunity”.

Surprising result

The fact that males kill those of other species is an intriguing finding, as it questions the constraints on and perfectibility of adaptation, says ecologist at the Smithsonian Tropical Research Institute in Panama. He would like to see this result in other non-pollinating wasp species to see whether the same pattern holds up more widely.

Ecologist at Harvard University agrees that the cross-species fighting is an interesting and surprising result. But she says that fighting is not limited to males. Her team found last year that in some pollinating fig-wasp species, the females do the fighting. “For these females the scarce resource is not mating partners, but egg-laying sites,” she says.

Thankfully, this war is not raging in the figs we eat. The fruit farmed by humans is a different species of fig that has separate wasp-producing and seed-producing trees. We only eat figs from the seed-producing trees, which do not contain any wasps – apart from, perhaps, the disintegrated bodies of the few females that originally pollinated them.

Journal reference: Ecological Entomology, DOI:

Wall paintings in Grotta Paglicci, Italy (Image: Stefano Ricci)

Going on the palaeo diet? Don’t put down your porridge just yet. Hunter-gatherers ate oats as far back as 32,000 years ago – way before farming took root.

This is the earliest known human consumption of oats, say Marta Mariotti Lippi at the University of Florence in Italy and her colleagues, who made the discovery after analysing starch grains on an ancient stone grinding tool from southern Italy.

The Palaeolithic people ground up the wild oats to form flour, which they may have boiled or baked into a simple flatbread, says Mariotti Lippi.

They also seem to have heated the grains before grinding them, perhaps to dry them out in the colder climate of the time. Mariotti Lippi notes that this would also have made the grain easier to grind and longer-lasting.

This multi-stage process would have been time consuming, but beneficial. The grain is nutritionally valuable, and turning it into flour would have been a good way to transport it, which was important for Palaeolithic nomads, she says.

Cereal fuel

To see the benefits of a plant-based diet, you only need to know that society has been largely fuelled by processed grains for the last 10,000 years, says archaeologist of University College London. “There is a relationship there to be explored between diet, experimentation with processing plant food and cultural sophistication.”

This is another example of the advances made by Europe’s Gravettian culture, which produced technology, artwork and elaborate burial systems during the Upper Palaeolithic era, says at Washington University in St Louis, Missouri. “These people were described 15 years ago as ‘Hunters of the Golden Age’, and the details of that are still being filled out.”

Mariotti Lippi’s team hopes to continue studying ancient grinding stones to find out more about the Palaeolithic plant diet. Grinding stones go back a long way, says Trinkaus, and people may well have been pounding and eating various wild grains even earlier than 32,000 years ago.

“We’ve had evidence of the processing of roots and cattails,” but here we’ve got a grain, and a grain that we’re very familiar with,” says Pope. “If we were to look more systematically for ground stone technology we would find this is a more widespread phenomenon.”

Journal reference: PNAS, DOI:

Grinding stone from Grotta Paglicci, Italy (Image: Stefano Ricci)

Philae has not phoned home for a long time and its parents are getting worried. The lander on comet 67P/Churyumov-Gerasimenko has not made contact with its team since 9 July. It seems to have a faulty transmitter and may have moved slightly, blocking its antennae from Rosetta, the orbiter that relays commands between Philae and Earth.

“We do not fully understand what’s going on with Philae,” says Stephan Ulamec, the Philae lander project leader at the .

It seems that one of the craft’s two transmitters has a problem. Philae is programmed to alternate between transmitters, so the team has now instructed it to only use the working one. This command is blind, meaning it doesn’t require a response from the lander, so Philae will hopefully receive it when it is next woken up by solar energy.

But that doesn’t explain the whole problem. The pattern of sunlight on Philae’s solar panels changed between June and July, in a way that is not explained by changing seasons on the comet. This could mean that Philae has shifted position, possibly pushed by gas expelled by the comet, and so its antennae could be more covered or pointing in a different direction. Alternatively, it could simply mean that material previously shading Philae has disintegrated, says Ulamec.

Cosmic frustration

The comet’s increasing activity is not helping the situation. The livelier it gets, the more dust it generates, which confuses Rosetta’s star-tracking navigation system. Rosetta is therefore orbiting further from the comet than before, which will make contact harder, although not impossible.

Luckily, the team has already extracted all scientific data from Philae, although there is some housekeeping information about Philae’s internal workings that they haven’t been able to access. Until they connect to Philae, they cannot do more science. It is frustrating to have a working lander on a comet, without being able to use it, says Ulamec.

If the team does re-connect to Philae they will use its simpler instruments such as the camera and temperature sensors, which don’t require much instruction from Earth. If they can establish a long, steady connection, they may have a second attempt at using the drill to extract samples from the comet’s surface.

From next week, Rosetta will start using its own instruments to focus on the southern hemisphere of the comet. At this point communication with Philae will be harder, but Ulamec hopes the team can find a good compromise between Rosetta’s investigation and contacting Philae.

Despite the situation, the team remains optimistic. For a start, in its sheltered location Philae will not overheat as the comet approaches perihelion, the point closest to the sun in its orbit. Ulamec believes the window of opportunity to re-establish a connection with the lander will last until September or October. After this time, the comet will be moving further away from the Sun, and it will become too dark for Philae to function.

Video: Shimmery sea sapphires disappear in a flash

Red and blue and green and violet and
 Invisible. Sea sapphires have been described as “the most beautiful animal you’ve never seen”. Even when you do see them, they can vanish in an instant (see video, above). But how do they pull off their trick?

This tiny crustacean has alternating layers of hexagonal guanine crystals and cytoplasm on its back that reflect light in a sparkling array of hues. Different species shimmer in different colours, ranging from gold to blue.

The colour is determined by the distance between the crystals and the angle at which light hits them.

In blue sea sapphires, the distance between the crystals is about the same as the wavelength of blue light, so the animals appear blue.

The angle of light hitting the sea sapphire also affects the colour and lets it perform its disappearing act. For the species in the video, for example, the animal’s tilt of 45 degrees causes the reflected light to slip into the ultraviolet spectrum, and the animal becomes invisible to our eyes.

Only the males have these amazing colours, the females are completely translucent. Males swim in spirals, probably to show off their shimmering hues to potential mates, says at the Weizmann Institute of Science in Rehovot, Israel.

“An intriguing question that still remains is whether the differences in colour are genetic and each male is born with a defined colour, or whether they can control the reflected colour,” says Addadi.

Understanding how the light reflection trick works could inspire new reflective or anti-reflective coatings in glasses, mirrors and optical display systems, says Addadi.

Journal reference:

Time could be running out for the polar bear (Image: Roberta Olenick/Getty)

One of the last hopes that polar bears may be able to weather the changing climate and break-up of their icy habitat has just been dashed.

The bears are facing longer periods without the sea ice on which they depend for hunting seals, and some spend the months between August and October on shore.

The hope was that during ice-free months, , the bears could slow down their metabolism to winter hibernation levels without going to sleep – so-called “walking hibernation”.

But a new analysis of 30 polar bears in the Beaufort Sea near Canada now shows that although the bears do slightly reduce their activity and body temperature in the summer, they do not reduce it enough to maintain body weight and improve their chances of survival.

This reduction in activity and body temperature is probably an emergency response to lack of food rather than a form of hibernation.

“It definitely is not good news,” says at the University of Wyoming in Laramie.

Challenging conditions

His team fixed movement-measuring devices to 26 polar bears and implanted temperature loggers into 17 bears in the Beaufort Sea.

Tracking the bears on the sea ice was not easy. The research required 200 people, several helicopters and a month-long stint on an icebreaker to complete.

“Logistics were so challenging and so all-encompassing that I really doubt that anyone will be going to the sea ice to measure these bears again,” says Whiteman.

However, there are a lot data still to be analysed from this project, which should tell us more about the relatively unknown physiology of polar bears and how adaptable they may be to the warming Arctic.

Whiteman’s team has already found that between August and October, the bears were less active than during their hunting season, which runs from May to July, but were still much more active than during hibernation. They were active for 25 per cent of the time during the hunting season and for 12–22 per cent of the time between August and October – compared with just 1–2 per cent of the time during winter hibernation.

Also, animals stranded on shore and those left on retreating ice showed similar patterns of activity and body temperature. The response of their bodies was similar to that of food-deprived mammals, not hibernating bears.

Reason for concern

This suggests that polar bears will not be able to adapt to melting sea ice simply by saving energy – which is something to factor in to future models of polar bear numbers. Current models do a lot of “guesstimating” about bears’ summer metabolism, says Whiteman.

at the University of Alberta in Edmonton, Canada, says that this “is one more reason why we should be very concerned about the long-term conservation of polar bears”.

“In many areas, polar bears are already close to their fasting limits, and other studies show that declines in reproduction, survival and population size will follow.”

Journal reference: Science, DOI:

Direct route to fear

The makings of a scream

Journal reference: Current Biology, DOI:

(Image: Rimba Group)

A leopard may not be able to change its spots, but it can hide them. The trick involved is simply black fur. Now an easy camera hack can reveal them again.

from James Cook University in Queensland, Australia, and his colleagues came up with the technique while studying the peculiar leopard population on the Malay Peninsula, where almost all the animals are pitch black.

Although there are often black-furred individuals in many species of mammals, it is very rare for this colouring, linked to the pigment melanin, to dominate an entire population.

Efforts to count and monitor the population were hindered by the impossibility of telling individuals apart until the team came up with a way of bringing defining marks to light. By simply blocking the light sensor on a consumer automatic camera, they were able to activate its flash in daylight to produce infrared images of spots (see top image).

(Image: Rimba Group)

The trick has helped the team identify 94% of the black leopards in the north-east of the Malaysian part of the peninsula. The team plans to use it for population counts in other parts of the region, too, especially in areas where poaching is being blamed for declining numbers.

Habitat loss is also affecting the population as forests are cut down for timber. Leopards on the island of Java are facing similar problems, but this recent portrait of a carefree male doesn’t capture any signs of stress.

Journal reference:

The size of a woman’s grey matter could depend on her dependence (Image: Piotr Powietrzynski/Getty)

Don’t do drugs, kids. Especially if you’re female. Women dependent on stimulants like cocaine and methamphetamine appear to have less grey matter, even after they stop using them. Weirdly, men’s brains don’t show this difference.

The brain regions most affected are those involved in reward, emotion and learning – although it isn’t clear yet whether the smaller than average size of these brain areas could be a cause or effect of addiction. , at the University of Colorado Hospital in Aurora, hopes these results will help lead to a better understanding of sex differences in substance abuse, and better, more distinct treatments for women.

Tanabe’s team used MRI scans to measure the brain volumes of 59 people previously dependent on stimulants and compared them with people who have never been dependent on these kinds of drugs. On average, the 28 women who had formerly been dependent on a stimulant drug had a smaller volume of grey matter in their prefrontal cortices, temporal lobes, insulae and other regions. This effect was not seen in men.

Shrinking brains

The women who had been addicted also differed in their personalities – on average, they were more impulsive and more reward-driven. We already know that women respond differently to stimulants: they start taking the drugs earlier, and may have more difficulty quitting. It’s possible that this pattern of female addiction could be linked to the brain size difference.

However, it’s unclear whether less grey matter causes female addictive behaviours, or if addiction might shrink these brain regions. “The question of causality is complex. There is evidence for both pre-existing and post-drug changes in brain structure and function,” says Tanabe.

from King’s College London says longitudinal studies, which follow the same people over time, are necessary to untangle the causes and effects before any treatment decisions could be based on this research.

Currently, men and women receive the same treatment for stimulant dependence. from Yale University suggests that the female brain may be more vulnerable to toxic effects of drugs and this study “would suggest extended treatment is necessary – perhaps more so for women”.

Journal reference: Radiology, DOI:

(Image: Sagehen Creek Field Station)

And for my next trick I will make a whole building vanish. This invisible barn seems to melt into the forest, confusing passers-by.

Built at the University of California’s it was designed by Seung Teak Lee and Mi Jung Lim from design firm , who wanted to create a structure with an understated shape that emphasises its surroundings. “Many architects and designers consider nature as just a background,” says Lee. “We thought it could be interesting to flip this.”

(Image: Sagehen Creek Field Station)

The whole barn, which measures just a metre at its widest point, is wrapped with reflective panelling to make it blend into the background, while the angled reflections of tree trunks hint at its true shape.

Judging by how confusing the structure looks to human eyes, you might expect it to baffle birds as well. However, it has been specifically designed with avian sight in mind. The mirrored film reflects wavelengths visible to birds more intensely so they can see it and avoid it.

Novel materials can also be used to make things invisible by bending light around objects. Two devices that cloak objects by bending light in the range visible to humans were able to conceal tiny microphones placed on a wall.

(Image: NASA/JPL-Caltech)

This is what the sun would look like if you had X-ray vision. The portrait, which combines images captured by three telescopes earlier this year, highlights active regions of the star that give off high-energy radiation.

NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, captured high-energy X-rays which are present in the most energetic spots, represented in bluish-white. Japan’s Hinode spacecraft picked up low-energy X-rays, depicted in green, while NASA’s Solar Dynamics Observatory imaged areas with extreme ultraviolet light, shown in yellow and red.

In active regions, where temperatures can reach millions of degrees, massive eruptions on the surface called flares spew out charged particles and high-energy radiation. NuSTAR’s high sensitivity means it can only view smaller flares that are less energetic. Its observations could be useful to help measure the energy they produce, as well as detecting nanoflares – even less energetic eruptions.

It’s rare for NuSTAR to pick a subject so close to home. Most of the time, it peers into deep space, producing super-sharp snaps.

In 2013, it captured the first images of the high-energy cosmos, revealing two black holes and a supernova remnant.