How is city noise good for insects?

Some of our readers probably remember ourmaterial about the benefits of walking in the parks. We mentioned that while walking surrounded by nature, a person rests from the city noise emitted by cars, trains, airplanes and construction works. With prolonged exposure to high noise levels, people can often experience aggression, increase blood pressure and, of course, deteriorate hearing. Even insects feel the harmful effects of noise, but for some of them urban noise is vital because it protects them from deadly parasites.

In the photo - a grasshopper. They should not be confused with crickets

It's about living on the territory of NorthAmerican crickets species of Gryllus lineaticeps. They, like many other insects, attract females to mating with the help of loud sounds. Unfortunately, the chatter published by their wings attracts the attention of not only females, but also parasitic flies of the species Ormia ochracea. These creatures fly to the sound and plant larvae either directly on the body of a cricket - in a week small flies hatch from the larvae and the insect dies. Sometimes this way destroys more than 60% of the population of North American crickets.

Crickets of the species Gryllus lineaticeps

How do insects breed?

However, stinging insects eventually foundat least two ways to disguise themselves from parasites. In 2004, American biologists noticed that some crickets of the species Teleogryllus oceanicus completely stopped making sounds. They became very cunning - to find a female, they began to move closer to their "singing" relatives and wait for the approach of several individuals of the opposite sex. Thus, helping each other multiply, crickets practically nullified the infestation by parasitic flies.

Cricket and parasitic fly Ormia ochracea

Scientists are not exactly sure yet, but in a second wayProtecting crickets from deadly flies can be a disguise in an urban setting. The fact is that, against the background of the noise of urban transport, the crickets chirps are almost inaudible for parasites. Scientists found this out during an experiment in the mountains of the California city of Santa Monica.

By the way, here's an article on the topic: How do parasitic mushrooms turn ants into zombies?

Pros of city noise

The essence of the experiment was thatResearchers found two speakers in the mountains. One of them played a recording with the sound of crickets, and the second - a recording of cars moving along city roads or the sound of the ocean. Since parasitic flies are usually active at night, 20 minutes after sunset, traps in the form of wooden planks with glue applied to them were placed on the way to the speakers. By changing the volume of sound in different dynamics, scientists found out how much city noise prevents flies from detecting victims.

The video below shows how larvae hatch from the body of an infected cricket. Warning: frames can be very unpleasant.

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After examining 60 traps, the researchers found thatwhen the volume of the speakers with city noise rises, the flies really pay less attention to cricket singing. It is because of this that scientists have suggested that city noise has a positive effect on the survival of crickets. But the question remains - how does ambient noise affect their reproduction? Scientists are left to conduct another study and find out if noise pollution does not prevent females from finding males.

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Harm of city noise for people

Perhaps scientists have found the first and onlypositive effect of city noise. Otherwise, it does only harm, worsening our hearing and irritating the nervous system, which ultimately can cause more serious diseases. According to statistics for 2017, the noisiest cities in the world are Istanbul, Barcelona and Paris. Moscow was in fourth place, so many of us should at least walk more in the parks and give our ears a rest.

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