Back in the 1860s, a British scientist named Henry Walter Bates noticed something interesting in the animal world: a kind of butterfly, Common Mormon, can change the pattern on its wings so that it looks like another butterfly species, the Common Rose, which is poisonous for birds to eat.

    Bates argued that animals develop this ability to protect themselves from being eaten. This theory had been widely accepted by scientists. But one question remains: how do these animals manage to do that?

    After more than 150 years, scientists are finally able to answer that question-it is all down to a gene(基因) called “doublesex", according to a study published on March 6 in the journal Nature.

    In fact, scientists have long known that genes are responsible for this useful ability. But until the new study, scientists hadn't been able to find out which genes in particular were responsible.

    Scientists at the University of Chicago compared the genetic structures of the Common Mormons that changed their wing patterns with those of ones that did not. And all the results pointed to a single gene, “doublesex”.

    This was much to the scientists' surprise. They used to expect that something as complex as this would be controlled by many different genes. For example, one gene would control the color of the upper part of the wing, one would do so for the lower part.

    However, the “doublesex” gene doesn't quite do everything by itself. Instead, it acts like a switch-it “tells” other genes to change the wing patterns. Isn't that clever?

    Scientists believe that this special ability of the “doublesex” gene on Common Mormon was developed throughout the long history of evolution. “The harmless species gains an advantage by resembling something predators(捕食者) avoid,” Sean Carroll, a scientist told Nature. “it was obvious evidence for natural selection.”

    ARCHAEOLOGISTS (考古学家) GUIDED BY laser images of a remote region of northern Guatemala have discovered 20-foot-high walls, watchtowers, and other evidence that ancient Maya societies had been annoyed by warfare threat over many years. The finds have upended long-established impressions of a civilization that it tamed the jungle and built thriving cities, then declined and disappeared quietly beneath the dense tropical forest.

    Among the most surprising discoveries was a large stone complex now called La Cuemavilla. Built on a steep ridge, the heavily fortified site included high walls. Moats which serves as the largest defensive system ever discovered in the region.

    This was surprising says an archaeologist, because we had a tendency to romanticize Maya warfare as something that was largely ritualized. But the fortifications were seeing suggest an elevated level of antagonism over centuries. Rulers were so deeply alarmed that they felt the need to invest in all these hilltop fortifications. There is an almost visible sense of fear in this landscape.

    All these findings owe credit to PACUNAM LIDAR Initiative, a laser survey of some 800 square miles of the Maya Biosphere Reserve in northern Guatemala. Using revolutionary Laser technology, the survey revealed the long-hidden ruins of a sprawling pre-Columbian civilization that was far more complex and interconnected than most Maya specialists had supposed.

    Guided by the new Laser treasure maps, the LIDAR team deployed through the jungle over the past year to conduct hands-on investigations of more than a dozen of the most promising sites-most of which would have been imperceptible without LIDAR.

    "You could walk over the top of a major ruin and miss it, "says an archaeologist who's part of the PACUNA project. But LIDAR picks up the patterns and makes the features pop out with surprising clarity.

    Three-dimensional maps generated by the survey yielded surprises even at Tikal, the largest and most extensively explored archaeological site in Guatemala. The ancient city was at least four times bigger than previously thought, and surrounded by a massive ditch and fortified base stretching for miles.

    Archaeologists stress that LIDAR, for all its utility, will never see below the ground or yield direct dates of occupation. "We still need to dig and hack our way through the jungle, but now we have a very accurate map to guide us."

    Some spiders hunt on the ground, others build webs to trap their food, but the grass water spider catches its prey by running along the surface of the water.

    This special water spider lives on the grassy banks of streams where mosquitoes, damsel flies and other insects come to feed and breed.

    Although it is one of the largest spiders in New Zealand, it has an unusual ability. It doesn't disturb the water as it waits for its meal, and there is barely a ripple(波纹) when it skims(掠过) across the surface at lightning speed to catch its prey.

    Grass water spiders deal swiftly with larger insects like damsel flies by pulling their heads under the water and holding them there until they drown.

    After a meal, the grass water spider spends up to half an hour grooming(修饰) itself. It wipes its eight eyes, brushes its antennae(触角), and takes special care to clean the hairs on its body.

    It is the hairs that trap tiny bubbles(泡沫) of air so that the spider can run down a blade(叶片) of grass and stay underwater for up to an hour when it is frightened. The hairs also keep the spider dry, even underwater.

    It is only when the female spider is caring for the young that she does not hunt on the water. After mating, she produces a large egg sac(囊), which she carries around for five weeks. Once the eggs start to hatch, she attaches the sac to some blades of grass or a thistle. She then tears the sac open and releases the tiny spiders into the nursery web.

    NAIROBI­Tin Tin, a Chinese restaurant located in central Nairobi, has been serving local Kenyans for nearly four decades with its delicious dishes and unique cultural background.

   "This is a restaurant definitely worth a try," said Steven, a local resident in his 30s. "It has provided Chinese food since my grandfather's time."

    According to Henry Tin, the restaurant owner, Tin Tin was established in 1978 at the heart of the Nairobi Central Business District, upholding Chinese cuisines while adapting to Kenyan preferences.

    For years, it has become a defining part of the city's landmark­Kenya International Conference Center­attracting lots of office workers nearby and even presidential customers.

   "The former president of Kenya, Moi, was a very good customer for us. He came almost always in cash. Then former president Mwai Kibaki and now president Uhuru. They all like to enjoy our food," Tin said.

    Danis, an office worker of an insurance company near the KICC says he is a frequenter of the restaurant.

   "It is the only Chinese restaurant in the highly competitive downtown area. Besides, its food has been adapted to our taste," Danis said, "My favorite dishes are fried shrimp and fried pork, which you can also find in a Kenyan restaurant."

   "High­quality food consistently served over the decades has helped maintain loyal customers," Enoch Kivunaga said, at Tin Tin.

   "My experience depends on the customers. If I cook good food, they always come back, whether they are presidents or ministers," he said.

    Tin said he speaks Swahili well and perfectly pronounces local names, which shows the Chinese culture and its Kenyan counterpart are quickly combining. "I am a Kenyan Chinese. I love both great countries."

    Get top tips from an expert photographer while you are taking digital photographs in the Garden at Kew.

Event details

    Wednesday 13 – Thursday 14 February, 2019

    Time: 10:30 am – 4 pm

    Place: Kew Gardens

    Course Fee: £160

About the course

    This course is designed for camera-owners who would like to know the basics. It will explain some of the basic principles of photography such as focus and exposure as well as many of the practical aspects such as how to download and store images.

    The great part of the time will be spent practicing techniques by actually using cameras out in the beautiful gardens at Kew. There will be many opportunities to ask questions, review your own images and learn some top tips.

    This course is suitable for people with any sort of camera. It is useful to bring along instructions books, and you'll need to make sure your batteries are fully charged and your memory card has some free space on it.

About the tutor

    Edward Parker is an expert tree and forest photographer who, over the last 20 years, has worked in more than 40 countries around the world. He has written more than 30 educational books and his photographs have been on exhibition at Kew Gardens, Downing Street and the Horniman Museum. Photographing Trees is his latest book.

How to book

    Email adulated@kew.org with a contact number, or call at 020 8332 5641.

    Along the river banks of the Amazon and the Orinoco there lives a bird that swims before it can fly, flies like a fat chicken, eats green leaves, has the stomach of a cow and has claw s ( 爪) on its wings when young. They build their homes about 4.6m above the river, an important feature for the safety of the young. It is called the hoatzin.

    In appearance, the birds of both sexes look very much alike with brown on the back and cream and red on the underside. The head is small, with a large set of feathers on the top, bright red eyes, and blue skin. Its nearest relatives are the common birds, cuckoos. Its most striking feature, though, is only found in the young.

    Baby hoatzins have a claw on the leading edge of each wing and another at the end of each wing tip. Using these four claws, together with the beak (喙), they can climb about in the bushes, looking very much like primitive (远古的) birds must have done. When the young hoatzins have learned to fly, they lose their claws.

    During the drier months between December and March hoatzins fly about the forest in groups of 20 to 30 birds, but in April, when the rainy season begins, they collect together in smaller living units of two to seven birds for producing purposes.