In October, Medflies (地中海果蝇) were discovered in an area of Los Angeles. California is a big farming state, and this was serious news for farmers. The solution to the problem may seem a little unusual; releasing (释放) millions more of the Medflies. Medflies lay their eggs in over 300 kinds of fruits and vegetables. When the eggs hatch (孵化), they can ruin these fruits and vegetables. The problem is that it can be hard to know that the Medflies are there until it’s too late. That’s because the fruits and vegetables still look normal even after the eggs are laid inside. So the damaged fruits and vegetables can be sent to other places allowing the Medflies to spread.

Three Medflies were discovered in a Los Angeles neighborhood called Leimert Park in October. The government set up a large quarantine (隔离) area, which means that no produce can be moved out of that area. That may seen extreme, since only three Medflies were found. but experts believe there are probably more out there.

Luckily, California has developed a program to control Medflies, and it has been working well for 30 years, The plan is to use planes to drop millions of male Medflies over the area. That may sound like a bad idea, but it’s actually a good way to make sure that Medfly numbers go down. Those Medflies are treated so that they can’t help produce new Medflies. This means that even though they can mate with female Medflies, the eggs produced will never grow or hatch.

The government says that the number of infestations (times when Medflies are found) has been cut by over 90%. To deal with the problem in Leimert Park, the government will be dropping two airplane loads of such Medflies every week.

Paired up in the right setting, dogs and horses can have their fair share of fun—at times even playing together and mimicking each other's facial expressions, new research suggests. These findings, published in the journal Behavioural Processes, mark the first example of so-called rapid facial mimicry occurring between play partners of different species, and indicate the existence of a universal language of play. Though the purpose behind play remains unclear, scientists believe the behavior arises to help animals improve hunting and social skills, relieve stress or develop relationship with each other, study author Elisabetta Palagi says, an animal behaviorist at the University of Pisa in Italy.

Learning more about the contexts in which different animals play around—especially across branches of the tree of life—could tell researchers a lot about play's origins and evolution. But apart from a handful of studies featuring humans and their pets, scientists haven't had many chances to analyze examples of interspecies play.

In 2018, when someone sent Palagi a YouTube video featuring a dog and a horse playing together, she took the chance to research further. The two species, she noted early on, were especially good research objects of interspecies friendship, because they had both been shown to recognize facial expressions in other animals.

Putting together a team of research students, Palagi began to collect and analyze hundreds of other videos with dogs and horses partnering in play. Only 20 videos ended up meeting the team's requirements: showing animals freely playing on their own, without human interference, for at least30 seconds.

Several common themes quickly arose. When playing, dogs and horses often mirrored each other's moves, jumping and pushing at each other. They also rolled on their backs and showed their throats and stomachs—a strong sign that they were at ease and even communicating their friendly intentions. Despite millions of years of evolution between them, the two species had found common ground for the only purpose of fun, said Palagi.

The two animals also frequently copied each other's facial expressions, both using the relaxed, open mouths—behayior that had never been noted between a pair of animals of different species. Horses and dogs may look and behave in extremely different ways, says Barbara Smuts, a behavioral ecologist at the University of Michigan who wasn't involved in the study. But fun is perhaps a language that doesn't need to be taught. Two very dissimilar animals, Smuts says, can still discuss how to play in a way that's comfortable for both.

Scientists have long debated how the bird ancestors evolved the ability to fly. The ground-up theory assumes they were ground animals moving fast by jumping and flapping（ 振 翅 ）their wings. The tree-down theory assumes they were tree climbers that glided（滑行）among branches.

At field sites Ken Dial saw a pattern in young ground birds. They flapped their half-formed wings, making short jumps into the air like popcorn. So to come up with new data on the age-old debate. Ken Dial designed a project to see what clues might lie in how baby birds learned to fly.

He settled on the Chukar as a model species，and brought in some hay bales（千草团）for the Chukars to rest on as a local farmer suggested. To his surprise, instead of lying up, the baby Chukars were using their legs. They run right up the side of a hay bale, flapping all the while. For Ken, this was the“aha” moment, which opened a world of possibilities.

Ken conducted more experiments, filming the birds as they raced up inclines（纤）tipped at increasing angles. As the incline increased, the birds began to lap, but they angled their wings differently from birds in flight. They aimed heir flapping down and backward, using the force not for lift but to keep their feet firmly pressed against the incline. It's exactly like the spoiler on the back of a race car. In Formula One, spoilers are the big aerodynamic（空气动力）fins that push the cars downward as they speed along, increasing power and handling

Ken called the technique WAIR, for wing-assisted incline running. It not only allowed young birds to climb vertical surfaces but also gave adults an energy-efficient alternative to lying In an evolutionary context, WAIR takes on surprising explanatory powers. Ken came up with a reasonable origin for the flapping strokes of birds (something gliding animals don't do and thus a shortcoming of the tree-down assumption) and an aerodynamic function for half-formed wings (one of the main drawbacks to the ground-up theory).