During summer days, warmer temperatures bring pests like mosquitoes. Mosquitoes can cause lots of trouble for people.【小题1】. They even can spread many serious diseases.

An easy way to protect yourself against mosquitoes is using repellents (驱虫剂). Joseph Conlon, an advisor of the American Mosquito Control Association, recommends using repellents that are registered with the Environmental Protection Agency, which ensures that they actually do no harm to humans. 【小题2】. But some repellents can provide 4-6 hours of protection if the quality of them is excellent.

Mosquitoes are also very weak. A slight wind from a fan can help keep them away from you. It turns out that many mosquitoes are not very good fliers. 【小题3】.

Another way is to clear all the standing water (积水) every five days. Conlon explains that mosquitoes can produce young in water collected in areas as small as bottle caps. But they have a limited flight range, which means they can’t travel far. “The best way to avoid them is to not have them around in the first place.” he says. If you’ve got them in your backyard, it’s because you’re raising them in your backyard. 【小题4】. “If you can’t avoid the standing water around your house, I suggest raising fish that will eat mosquito larvae (幼虫).”

【小题5】. They’ve experimented with male mosquitoes containing some materials that stop females from producing larvae. “There are not a lot of companies producing new chemicals or treatments that we can use,” a researcher of the experiment adds. “We need new technologies and products to get rid of mosquitoes.”

After years of heated debate, gray wolves were reintroduced to Yellowstone National Park. Fourteen wolves were caught in Canada and transported to the park. By last year, the Yellowstone wolf population had grown to more than 170 wolves.

Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

The disappearance of the wolves had many unexpected results. Deer and elk populations — major food sources (来源) for the wolf — grew rapidly. These animals consumed large amounts of vegetation (植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park’s red foxes, and completely drove away the park’s beavers.

As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

The government spent nearly 30 years coming up with a plan to reintroduce the wolves. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

It’s been a hard time for rhinos (犀牛) lately. Recently the International Union for Conservation announced the western black rhinos had died out in the wild. It was last seen in western Africa in 2006. Now, those who work to protect the animals are trying to make sure that won’t happen to other rhinos.

19 south-central black rhinos in South Africa were driven to an area nearly 1,000 miles away, which was said to be the gentlest and quickest way to transport the animals. They were taken to a new home that would keep them safe from hunters.

Though it is not allowed to hunt rhinos, many are still killed for their horns, which can sell for as much as $30,000 each. Most of them are used to make drugs as traditional medicines in Asian countries. Some people believe that the horns work well in treating pain, fever and even cancer. However, there is no medical evidence yet.

Black rhino population began falling rapidly in the second half of the 1900s because of poaching. In fact, some people still hunt the animals at the risk of being put into prison. And many of the places where the animals used to live in were destroyed when people started building farms on the grasslands. Until the 1960s, about 65,000 black rhinos lived throughout most of Africa. Today, fewer than 5,000 are left — most of them in zoos and wildlife reserves.

South Africa has the largest population of rhinos in the world. Poaching is an especially big problem in that country. So far, more than 340 rhinos have been killed there. Since 2003, the Black Rhino Expansion Project has been helping the south-central black rhinos in South Africa. The group works with landowners to find areas where rhinos can live safely away from hunters.

So far, the group has successfully saved about 120 rhinos. Leaders of the project say the south-central black rhinos have seen a rise in numbers. It is hoped that, with continued support, these rhinos can escape the unfortunate result of the western black rhinos.