Arkansas scientists examine mosquito listening to; can assist scale back their populations

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According to the U.S. Department of Agriculture, mosquitoes are among the deadliest living things when it comes to human death. Since the beginning of time, these arthropods have spread diseases such as malaria, West Nile, dengue, yellow fever and others. It is estimated that 1 million people worldwide die from mosquito-borne diseases each year.

Hordes of blood-sucking creatures can devastate livestock and animals can become sick, lose weight, or even die from blood-borne diseases. Estimating the damage caused by arthropods can be difficult, but the USDA estimates that at least $ 100 billion in damage is caused by these insects worldwide each year.

Arkansas, like many other southern states, has a long history of fighting mosquitoes, and this problem only worsened decades ago when the state became the leading rice producer in the U.S. Rice fields are typically covered with water for long periods of time, making it an ideal growing environment for mosquitoes.

Scientists have tried to come up with pesticides and other measures to curb mosquito growth in the state, and now they are trying to find other ways to deal with it. Part of this process is understanding how these insects behave.

Researchers have found that mosquitos’ ability to hear and respond to sounds is more complex than previously thought, said Emily McDermott, assistant professor of entomology at the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.

McDermott’s research assistant Cassie Steele, a Ph.D. Student at Dale Bumpers College of Agricultural, Food and Life Sciences, authored a research paper examining numerous studies examining the biology of mosquitoes’ hearing and how they use what they hear.

Steele and McDermott began the survey two years ago when they were both working at the Walter Reed Army Institute of Research in Maryland. It was published by the Entomological Society of America this summer.

According to Steeles and McDermott’s paper, mosquitoes have antennae ears that vibrate in response to sound. The vibration is transmitted to a biomechanical structure, the Johnston organ, and from there to the central nervous system, through which the mosquito perceives sounds.

There are differences in the structure of the hearing of male and female mosquitoes, which suggest that the antennae of the males are more sensitive.

Female mosquitoes might locate other animals, including humans, by sound, McDermott said, but the evidence is not clear. Although research shows that mosquitoes react to sounds in the range of human speech, the bigger pull is likely the carbon dioxide that humans emit when they speak. Mosquitoes are also attracted to people by heat and smell.

While at Walter Reed, Steele said she was planning a study that would use recorded human voices to see if sound alone attracts mosquitoes. But she and McDermott left to come to Arkansas before the study started.

Steele hopes to resume this project next summer.

Mosquitoes primarily use their hearing to find partners, McDermott said. You can differentiate between species and gender based on the flapping of their wings. That opens the door to research applications.

Much of the ongoing research on mosquito hearing is focused on how entomologists can use it to monitor populations, McDermott said.

Mosquito-borne disease reduction programs have used sterile males, males that only give birth to non-viable offspring, and a bacterium that prevents Aedes Egypti mosquitoes from transmitting dengue fever. McDermott said audible traps could help scientists monitor these particular males to determine their survival in the wild.

“Trapping and monitoring is the greatest benefit to understanding and harnessing mosquito hearing,” said McDermott. “What we want to know is whether we will survive … does the trait survive in the population?”

The researchers cited in their investigation paper used live footage and synthesized versions of certain species’ flapping female wings to test their usefulness in monitoring males, Steele said.

Audible traps offer advantages over other types of mosquito traps, according to Steele. Using the flaps of certain female mosquitoes’ wings allows researchers to target males of certain species. The reverse is also true for studies in which females of certain species are desired.

Testing the use of recorded and synthesized mosquito sounds presents some challenges, Steele said. Research requires that the sounds be played in areas where the mosquito populations exist, which are often where people live.

“People don’t want to hear the mosquitoes buzzing all the time,” said McDermott. “It limits places and times we can use them.”

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