Perhaps some of our readers will remember our article about the benefits of walking in the parks. Did we mention that walking surrounded by nature man has a rest from the urban noise of cars, trains, aircraft and construction work. Prolonged exposure to high noise levels, people can often encounter aggression, to increase blood pressure and, of course, to deteriorate the hearing. Harmful effects of noise feel even insects, but some of them, the noise of the city is vital, as it protects them from deadly parasites.
We are talking about inhabiting the territory of North America crickets of the species Gryllus lineaticeps. They, like many other insects to attract females to mate with loud sounds. Unfortunately, published their wings chirping attracts the attention of not only females, but also parasitic flies of the species Ormia ochracea. These creatures are drawn to the sound and planted larvae either directly into the body of the cricket — a week later, the larvae hatch into small flies and the insect dies. Sometimes thus destroyed more than 60% of the population of the North American crickets.
How to multiply the insects?
However, the chirring of insects, over time, found at least two ways to disguise themselves from parasites. In 2004, American biologists have observed that some crickets of the species Teleogryllus oceanicus does no longer make sounds. They were very tricky to find a female, they began to move closer to their “singing” dogs, and to wait the approach of several individuals of the opposite sex. Thus, helping each other to breed crickets almost negated the contagiousness of parasitic flies.
Scientists still not exactly sure, but the second method of protection of crickets from the deadly fly can be masking in the urban environment. The fact that the background noise of the city traffic, the chirping of crickets is almost inaudible for parasites. Scientists have found that in the experiment conducted in the mountains of the Californian city of Santa Monica.
By the way, here's an article on the subject: Like mushrooms-parasites turn ants into zombies?
Pros the noise of the city
The essence of the experiment was that the researchers found in the mountains two speakers. One of them is reproduced the recording with the chirping of crickets and the second recording moving on urban roads cars or the sound of the ocean. As the parasitic flies are usually active at night, 20 minutes after sunset on the way to the speakers had placed traps in the form of wood applied with glue. Changing the volume on different speakers, scientists have discovered how urban noise interferes with the flies to detect victims.
The video below shows how from the body of an infected cricket larvae hatch. Note: frames can be very unpleasant.
Having studied 60 traps the researchers found that increasing the speaker volume with the city noise flies really pay for the sound of crickets less attention. Because of this, scientists have suggested that urban noise has a positive effect on survival of crickets. But the question remains — how ambient noise affects their reproduction? Scientists were left to conduct another study to find out and prevents noise pollution the females find the males.
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Harm city noise for people
Perhaps scientists have found the first and only positive effects from the city noise. Otherwise it brings only harm, hurting our ears and irritating the nervous system that may ultimately cause more serious diseases. According to statistics for the year 2017, the most bustling cities in the world are Istanbul, Barcelona and Paris. In fourth place was Moscow, so many of us should at least more walk through the parks and give your ears a break.