Have you ever heard of an insect called the cicada(蝉)? 【小题1】 But they have an interesting internal clock that tells them when to go aboveground.

Every 17 years, billions of the noisy Brood V cicadas(十七年蝉) will swarm(成群出现) to northeastern parts of the US, including New York, Ohio and Pennsylvania. 【小题2】But there are usually a lot less of them compared to the Brood V cicadas.

【小题3】 According to Discovery News, these insects started their lives in 1999. And as their 17-year life cycle comes to an end, they go aboveground when their underground homes get warmer 64 degrees Fahrenheit (about 18℃) to be exact.

Then the females will lay hundreds of eggs in trees, and after about four to six weeks, the mother and father cicadas will die. 【小题4】

While they can be kind of annoying, these insects don’t harm humans, but they do make a lot of noise during their time aboveground. 【小题5】

However, since there are so many of the 17-year cicadas, the amount of laid eggs can sometimes harm small trees and bushes. But after this summer, these insects will mostly mind their own business until 2033.

Throughout history, humans have assigned names to objects and each other as a means of efficient communication. Additionally, we often give names to animals that are close to us, such as our pets. To date, evidence has been scarce to indicate that animals engage in naming each other. However, an exciting new study indicates that elephants use unique sounds as a way to identify one another. Isn’t that fascinating?

A few animals, including parrots and dolphins, have been known to use sounds that are similar to names. Each dolphin invents a signature whistle that is unique to it, and other members of its species communicate with it by simulating this special call. The new study, led by Michael Pardo of Colorado State University, shows that wild African elephants use names in a way that is not just copying sounds and is much closer to the way humans use names.

For the study, the researchers recorded 625 sounds made by wild African elephants in Kenya that they called “rumbles (隆隆声)”. This is the most common type of call produced by elephants, and it can travel long distances — as far as 3.7 miles. It takes place at a very low frequency, which means humans can’t hear it.

The researchers analyzed the sounds using computers and found that certain rumbles were directed at specific elephants to get their attention They found that all the elephants in the herd used the identical call to get a particular elephant’s attention — these calls were not just nicknames used by one of the elephant’s friends. Also, unlike the way dolphins communicate, the rumbles were not just imitations of the elephant they were trying to communicate with.

The researchers then played back some of the recorded rumbles to the elephants. They found that elephants responded more to their own name than to other calls, coming toward it more quickly or calling back faster. Cartlin O’Connell-Rodwell, an elephant expert, said, “The study shows that elephants can still keep in touch with one another even across a large area.” She told Live Science, “The rumbles were magical, which allow them to spread out much further and still keep a watchful eye on individuals.”

Despite these efforts to prevent the spread of invasive (入侵的) species, they keep increasing across the planet. For example, the International Union for the Conservation of Nature (IUCN) has identified a list of the 100 “world’s worst” invaders that have spread across the planet, with little hope of controlling them. The list includes eight species of fish. They are highly valued by people for food or entertainment, and thus not only are they difficult to control, but people may not wish to control them. An example would be rainbow trout (虹鳟鱼). Although rainbow trout has demonstrated impacts on native species and ecosystems, this species is unlikely to be controlled soon.

The example highlights the difficult task in controlling biological invasions.Although control can work sometimes, this often can’t completely remove the invader. Furthermore, control isn’t always an option when invaders are species people desire, or control efforts harm native species.

Given the difficulty of preventing or controlling biological invasions, what should we do? One way is to focus on the impacts of invasions rather than the invaders themselves. For example, it may be possible to manage the undesirable impacts without fully controlling them. This approach is like managing undesirable symptoms of a disease that cannot be cured. For invasive species, undesirable symptoms are the negative impacts on native species or ecosystems.

Managing the impacts of invaders needn’t be the only method. It can be combined with more conventional measures of prevention and control to design more effective strategies. Adding the option of managing impacts without the need for control opens up new opportunities for dealing with the challenges of managing biological invasions. We hope this will inspire people to work more closely to understand ways to minimize the threat posed by invaders as there seems no choice but to learn how to live with them.