A butterfly’s wings can have many jobs besides keeping the insect high up in the air. They may be used to attract mates, or to warn potential attackers to stay away. All of these roles, though, depend on their unchanging colouration. This plays into the idea that butterfly wings are dead tissue, like a bird’s feathers. In fact, that’s not true. For example, in some species males’ wings have special cells releasing some chemicals which attract females.

Nanfang Yu, a physicist at Columbia University, in New York, has been looking into the matter. Together with Naomi Pierce, a butterfly specialist at Harvard University, he has now shown, in a paper published in Nature Communications in February, 2020, that butterfly wings are, indeed, very much alive.

In their experiments, the two researchers used a laser(激光) to heat up spots on the wings of dozens of butterfly species. When the temperature of the area under the laser reached 40°C or so, the insects responded within seconds by doing things that stopped their wings heating up further. These actions included a butterfly turning around to minimize its profile to the laser, moving its wings up and down or simply walking away.

Butterflies engaged in all of these heat-minimising activities even when the researchers blindfolded them. That suggested the relevant sensors were on the wings themselves. Dr Yu and Dr Pierce therefore searched those wings for likely looking sensory cells. They found some, in the form of neurons(神经元) that were similar to heat detectors known from other insects. They also uncovered disc-shaped cells that appeared to be similar to pressure-sensitive neurons. They guess that these are there to detect deformation of the wing—information an insect could use to control its flight pattern.

The third discovery they made to contradict the “dead wing” idea was that some butterfly wings have a heartbeat. A butterfly’s wings have veins(静脉). These carry a bloodlike liquid which, researchers have now found in males, shows a pulse(脉搏) of several dozen beats per minute. The source of this pulse appears to be the scent(气味) pad, a dark spot on the wings that produces the female-attracting chemicals. Apparently, this “wing heart” acts as a pump that helps bloodlike liquid through the scent pad.

In all their experiments simulating different environmental conditions, Dr Yu and Dr Pierce consistently found that, different parts of the wing are covered by different sorts of scales(鳞屑). In particular, tubes pass through scales over the scent pads. This improves their ability to spread heat away and helps keep the living parts of a butterfly’s wings alive.

The world’s largest iceberg, named A68a, broke away from Antarctica’s Larsen C ice shelf in July, 2017. It has since floated(漂浮)toward the island of South Georgia in the southern Atlantic Ocean. Satellite pictures show the iceberg has remained in one piece. It is about 150 kilometers long and 48 kilometers wide. It is traveling at one kilometer an hour and is on a path to hit South Georgia in around 30 days.

Right now is the time of year when seals and penguins spend a lot of time caring for their young. This means the distance that parents have to travel to find food is important. Scientists fear that if the iceberg hits the island, it could prevent the penguins and seals from reaching food supplies. That means they have to go a lot further. They have to go around the iceberg, or to actually go further to find food. And that time is quite important at this particular period of their life cycle.

Ecologists say an iceberg crash(碰撞)would also disturb materials settled on the seabed, possibly polluting the surrounding seas. As the iceberg melts(融化), it would also send large amounts of fresh water into the ocean. This could affect krill populations that are a major source of food for the island's wildlife. Besides, the iceberg could remain for 10 years and change the area’s whole ecosystem. If some rare species fail in this area, their numbers globally are going to go down quite sharply.

The breaking-off of icebergs from Antarctica is a natural process. But the process is changing with climate change. What we’re seeing now is that the speed at which this is happening is increasing. And so, this might become more of a usual thing into the future. Right now, officials are hoping that changing weather patterns could direct the iceberg out into the open ocean, where it would, in time, break up and melt.

From the moa in New Zealand to the dodo in Mauritius (both of these two flightless birds have died out), the arrival of humans has often spelled extinction for tasty but previously isolated animals. Many scientists had assumed that the woolly rhinos (长毛犀牛) suffered the same thing. But Love Dalén, a professor at the Centre for Palaeogenetics in Stockholm. and Edana Lord, one of Dr Dalén's PhD students, are not so sure.

Until recently, information on the story of this great ice-age animal had been limited to the fossilized bones (骨骼化石). In the past couple of decades, however, scientists have learned to use a richer source of information： ancient genomes (基因组). By itself, DNA breaks down quickly, attacked by water and sunlight. But DNA covered in bones and teeth can survive longer, especially if those bones and teeth are themselves in permanent frozen land. It was this sort of DNA that enabled Dr Dalén and Ms Lord to investigate the woolly rhinos' disappearance.

Working with a team of colleagues, the researchers obtained DNA from 12 woolly rhino bones collected from permafrost in Siberia. Analyzing the genetic diversity of the bones, the researchers found that rather than declining as humans arrived, the population of rhinos remained stable from 29,000 years ago to 18,500 years ago, a few thousand years before they died out. Perhaps the people who met the animals found them distasteful. Or perhaps the rhinos were simply too dangerous to hunt with their simple weapons.

On the other hand, the animals' decline lines up suggestively with a rapid period of global warming that began around 14,700 years ago. The researchers argue that this was the more likely cause of the animals' disappearance. This time, it seems, it was Mother Nature who did it.