IT'S now commonplace to see train seats infested with bed bugs that cannot be killed by insect sprays and tube-dwelling mosquitoes that don't need to eat blood to produce babies.
Our sprawling cities are now home to these super strong nasties along with disease-laden rats and all manners of other disgusting creatures, reports The Sun.
Urbanisation is having some unfortunate consequences that could literally end up coming back to bite us, according to Marc Johnson, an associate professor of biology at the University of Toronto.
Using London as an example, he warned that disease-spreading mini-beasts might cause serious harm as they evolve in our cramped capital cities.
There are now mosquitoes that have evolved to live in the London Underground stations that no longer need to feed on blood to produce babies.
The critters, which can be found in New York and Los Angeles, have no need to become dormant during the winter.
Johnson said: "As we build cities, we have little understanding of how they are influencing organisms that live there."
Another itch-inducing example is bedbugs, which were scarce two decades ago but have adapted to become immune to insecticides and subsequently "exploded in abundance worldwide".
"It's good news that some organisms are able to adapt, such as native species that have important ecological functions in the environment," he told Phys.org.
"But it can also be bad news that the ability of some of these organisms to adapt to our cities might increase the transmission of disease."
In the first comprehensive study to look how organisms adapt to urban life Johnson, along with Jason Munshi-South, an associate professor of biological sciences at Fordham University, found that humans and cities are the largest drivers of evolution on the planet.
The research, which was published in journal Science, suggests that we need to think carefully about how we are encouraging the spread of species that may influence our lives for the worse such as rats, lizards, cockroaches and pigeons.
Update your news preferences and get the latest news delivered to your inbox.