In an article in the Journal of Medical Entomology in March 2023, mosquito researchers in Florida report the presence of in the state of Culex lactator, a species previously known from Central and South America. The arrival adds to the growing list of non-native mosquito species finding their way into Florida—a worrying trend for public-health entomologists. (Photos courtesy of Lawrence Reeves, Ph.D.)

By Ed Ricciuti

Ed Ricciuti

The news media have been abuzz about giant pythons slithering around Florida, the nation’s hotbed of invasive species, but tiny mosquito newcomers could pose perhaps a much more serious problem there. The recent discovery of another species added to the bevy of nonnative mosquito species established in the state—as many as 17—and highlights “the possibility that the introduced species will facilitate the transmission of a mosquito-transmitted disease,” says Lawrence Reeves, Ph.D., an entomologist at the University of Florida.

Reeves is lead author of a study published in March in the Journal of Medical Entomology on the discovery in Florida of Culex lactator, a tropical American species belonging to a group that includes important disease vectors. Although the species has not been tagged as a vector of any human diseases, Reeves says the discovery of its presence in Florida highlights the “need to be vigilant for introductions of new mosquito species, because each introduction comes with the possibility that the introduced species will facilitate the transmission of a mosquito-transmitted disease.”

Despite a study in Mexico that found Zika virus nucleic acid in Culex lactator, Reeves says, “if it is a vector of anything, it is most likely to be a vector for pathogens transmitted by other Culex species, like West Nile virus or St. Louis encephalitis virus. But, it’s important to emphasize that we currently don’t have any evidence that Culex lactator is a vector for anything—most mosquito species are not vectors of human pathogens.”

In an article in the Journal of Medical Entomology in March 2023, mosquito researchers in Florida report the presence of in the state of Culex lactator, a species previously known from Central and South America. Shown here are specimens of Culex lactator and two other related species that are highly similar in appearance. Note: Images not to scale. (Photos courtesy of Lawrence Reeves, Ph.D.)

Reeves and his team first collected C. lactator specimens in 2018 from rural sites in southern Miami-Dade County while looking for other recently introduced mosquitoes. They identified it using DNA analysis and other laboratory tools. Last year, scientists with the Collier Mosquito Control District and Lee County Mosquito Control District found Culex lactator in their counties, indicating that it is spreading.

Reeves doubts it will range much further north because of its tropical origins.

“It’s likely going to be limited by temperatures, particularly winter temperatures. It remains to be seen how far north it will go and how much cold it will be able to tolerate,” he says. “It’s possible that it could get up into more temperate regions in northern Florida or even beyond Florida, but we don’t have any reason to expect that it will.”

Because they are implicated in so many serious diseases, mosquitoes have been studied extensively. Even so, many gaps exist in knowledge of tropical mosquitoes, some of which are vectors of the worse diseases carried by these insects.

Lawrence Reeves, Ph.D., is an entomologist and research assistant scientist at the University of Florida’s Florida Medical Entomology Laboratory. Researchers and mosquito management professionals like Reeves collect samples of mosquitoes across the state to monitor where mosquito species are present and whether new species are entering the state. Here, Reeves uses a large device called an aspirator—”much like a vacuum,” he says—to collect mosquitoes from a wetland habitat. (Photo courtesy of Lawrence Reeves, Ph.D.)

Lawrence Reeves, Ph.D., is an entomologist and research assistant scientist at the University of Florida’s Florida Medical Entomology Laboratory. Researchers and mosquito management professionals like Reeves collect samples of mosquitoes across the state to monitor where mosquito species are present and whether new species are entering the state. Here, Reeves checks for mosquitoes in a trap. (Photo courtesy of Lawrence Reeves, Ph.D.)

Says Reeves, “We need to work toward identifying the pathways by which these mosquitoes are arriving in Florida, do what we can to prevent new establishments, and learn what we can about the poorly known mosquitoes of the American tropics, where the majority of our nonnatives originate.”

Invasive mosquitoes use myriad travel options. Adults hitchhike on vehicles and aircraft. Some have desiccation-resistant eggs that travel very well after being laid on the ground or in a container, like a tire. If soil or containers holding eggs are moved, the eggs have a good chance of surviving and hatching in a new home. However, says Reeves, “The curious thing about Culex lactator, and several of the other recent Florida invaders, is that we don’t expect them to have eggs that travel well. Likely, the eggs of these mosquitoes cannot survive periods of dryness. So, we don’t have any ideas that jump out as likely introduction pathways for Culex lactator and these others.”

The Culex lactator discovery came on the heels of the revelation by Reeves and his colleagues in 2020 that Aedes scapularis, a mosquito that can spread pathogens causing yellow fever, Venezuelan equine encephalitis virus, and other illnesses, is established in Florida. Previously, it was known from a specimen collected in 1945.

Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.