A couple of hormones work together to the desire of to activate or suppress mosquitoes according to blood , according to a study published today 1 .

The results reveal a possible mechanism that the attraction of mosquitoes on humans and other animals that have so far been a mystery. "The discovery could provide new pesticide goals to prevent the reproduction of mosquitoes and the transfer of diseases," says Zhen Zou, an entomologist at the Institute of Zoology of the Chinese Academy of Sciences in Beijing.

The females of most mosquito species-including aedes aegypti , the carrier of the viruses, the Dengue fever , yellow fever and Zika-diet to develop their eggs. But as soon as you have consumed a blood meal, your desire for blood ends until you have laid your eggs.

Michael Strand, an entomologist at the University of Georgia in Athens, wanted to understand the mechanism that controls this cycle of attraction more precisely. He noticed that the values ​​of a hormone that is produced in the intestine of the insect and is called neuropeptide f (NPF) rose when the mosquitoes were looking for a landlord and after they had drunk blood. "This has motivated us to check whether the presence of this hormone was a driving factor when looking for a blood meal," says Strand.

Together with his colleagues, mosquito-enthusiastic cells analyzed with his colleagues that produce hormones in the gastrointestinal tract. As expected, the NPF values ​​rose before the mosquitoes had a blood meal and fell six hours after they had eaten. The attraction of the mosquitoes on humans fit this hormonal swing: they showed no interest in a human hand on the day of their meal, but headed for it after they had laid their eggs. "There was an almost perfect reflection," says Strand.

Next, the researchers switched off the gene that NPF produces in female mosquitoes, and found that it reduced their attraction to people. When they injected the hormone into these mutied mosquitoes, their interest in people was restored, but it had little influence on mosquitoes that had eggs.

The team also found that certain neurons that range into the intestine produced another hormone called Ryamid that regulates the feeding behavior of insects. Just like NPF values ​​after a blood meal, the Ryamide values ​​rose. In the case of mosquitoes without eggs, an injection of Ryamid reduced their NPF values ​​and suppressed their attraction to human hosts, while the control mosquitoes-with natural hormone levels-were straight into a human hand. This indicates that NPF and Ryamid work together to stimulate and suppress the attraction of hosts in mosquitoes.

beach and his colleagues plan to examine other molecular factors involved in the attraction of hosts in order to create a more comprehensive picture. "Life is never easy," he says.