We know that Colony Collapse Disorder is the result of bees being stressed to death by a number of factors, but contagious illnesses transmitted by insects (and communicable by other means) can likewise be pressured out of existence if enough of the disease’s agents are countered until the system crashes. From “The Calculus of Contagion,” Adam Kucharski’s excellent Aeon essay about a mathematical approach to preventing potential pandemics like Ebola, a passage about Ronald Ross’ plan of attack for outmaneuvering malaria:

“To prove the connection between mosquitoes and malaria, Ross experimented with birds. He allowed mosquitoes to feed on the blood of an infected bird then bite healthy ones. Not long afterwards, the healthy birds came down with the disease, too. To verify his theory, Ross dissected the infected mosquitoes, and found malaria parasites in their saliva glands. Those parasites turned out to be Plasmodium, identified by a French military doctor who had discovered the bug in the blood cells of infected patients just a few years before.

Next, Ross wanted to show how the disease could be stopped, and his experiment with the water tank pointed the way. Get rid of enough insects, he reasoned, and malaria would cease to spread. To prove his theory, Ross, a keen amateur mathematician, constructed a theoretical model – a ‘mosquito theorem’ – outlining how mosquitoes might spread malaria in a human population. He split people into two groups – healthy or infected – and wrote down a set of equations to describe how mosquito numbers would affect the level of infection in each.

The human and mosquito populations formed a cycle of interactions: the rate at which people got infected depended on the number of times they were bitten by infected mosquitos, which depended on how many such mosquitos there were, which depended on how many humans had the parasite to pass back to those mosquitos, and so on. Ross found that for the disease to simmer along steadily in a population, as it did in India, the number of new infections per month would need to be equal to the number of people recovering from the disease.

Using his model, Ross showed that it wasn’t necessary to remove every mosquito to bring the disease under control. Destroy enough mosquitoes, and people infected with the parasite would recover before they were bitten enough times for the infection to continue at the same level. Therefore, over time, the disease would fall into decline. In other words, the infection had a threshold, with outbreaks on one side and elimination on the other.”