Culex antillummagnorum, a little-studied mosquito species found across the Caribbean, doesn’t lay its eggs in a tightly packed group like fellow Culex species. Instead, as a new study details, female Cx. antillummagnorum hover or perch above small pools of water in plants and drop in their eggs one at a time. They can be found where Heliconia caribaea bracts (left) collect rainwater. Cx. antillummagnorum females (right) hover over the bracts while launching eggs into the water—a first for the Culex genus. (Images originally published in Wynne et al 2025, Scientific Reports)

By Liz Wynne

Liz Wynne

In 1975, prolific mosquito systematist Peter F. Mattingly, Ph.D., received an unusual package in the mail. It was sent from his colleague, the entomologist J.N. Belkin, Ph.D., and contained mosquito eggs hastily stuck to a paper strip, along with the female that had laid them. The species was Culex antillummagnorum, an understudied member of the subgenus Micraedes found on islands across the Caribbean.

Belkin had encountered the species while sampling mosquitoes in Puerto Rico for the “Mosquitoes of Middle America” project. He recognized that there was something strange about this female Culex and her eggs, something that would cause Mattingly, an expert in the field, to re-evaluate his understanding of mosquito diversity entirely.

As Mattingly carefully unfurled the paper strip, he noticed that the Cx. antillummagnorum eggs were, as he wrote in his note, “quite unlike any other Culex” he had ever seen. From scientific literature to widely used college textbooks, all Culex mosquitoes are largely defined by their distinctive egg-laying behavior, where females glue elongated, cigar-shaped eggs together into floating “rafts” on the water’s surface.

Culex antillummagnorum eggs (top) are drastically different in appearance than the characteristic floating egg raft of other species in the genus (bottom). Cx. antillummagnorum eggs are white when first laid (top left) but turn dark brown after a few hours (top right). (Culex antillummagnorum eggs image originally published in Wynne et al 2025, Scientific Reports; egg raft image via CDC Public Health Image Library)

For decades, Mattingly had meticulously catalogued variation in mosquito eggs, mostly in medically important species like Cx. quinquefasciatus and Cx. pipiens, all of which lay the textbook-standard egg rafts. But the eggs from Cx. antillummagnorum were not glued together. They were not cigar-shaped either. Instead, the eggs were bright white, oval, and—even more fascinating—laid separately.

Their aerodynamic shape (similar to a rugby ball) reminded Mattingly of the eggs of Toxorhynchites, more commonly known as “elephant mosquitoes,” which the female launches from her abdomen in looping flight patterns above the water. But why would a Culex lay eggs like a Toxorhynchites?

In his note, published in the 1975 issue of Mosquito Systematics, Mattingly hypothesized: “If they [the eggs] are indeed those of a Culex, then this must be a most remarkable case of convergent adaptation to the toxorhynchitine mode of oviposition on the wing.”

The eggs suggested two things that had never been observed in the genus: egg-laying in flight and skip-oviposition (a “bet hedging” strategy in which females disperse eggs across various locations). Both behaviors exist in other mosquitoes, but never in Culex. Confirming either would challenge well-established beliefs about the genus.

Culex antillummagnorum has been a little-studied species of mosquito, but it is receiving new attention as the putative vector of lizard malaria circulating among anole communities in Puerto Rico. (Images originally published in Wynne et al 2025, Scientific Reports)

A Decades-Old Mosquito Mystery

Liz Wynne, a research technician at the University of Southern Mississippi, spent several weeks in Puerto Rico’s Luquillo Experimental Forest observing the unique egg-laying behavior of  instead began hiking out at dusk, night after night, to sit and observe the same cluster of Culex antillummagnorum mosquitoes. After initial failures, she found them in periods shortly after dusk near an old, partially buried, concrete septic tank that served as a daytime resting spot for female mosquitoes. Shortly after dusk, a buzzing cloud of mosquitoes would emerge from the small opening of the tank and fly toward the nearby Heliconia plants. (Photo courtesy of Liz Wynne)

More than 50 years later, I found Mattingly’s note buried under dust-covered stacks of Mosquito Systematics in the library of my advisor, Don Yee, Ph.D. Culex antillummagnorum had received new attention as the putative vector of lizard malaria circulating among anole communities in Puerto Rico, and I had planned to study the species’ life history for my undergraduate thesis, focusing primarily on its preference for ovipositing in the water-filled bracts of Heliconia caribaea, a large, evergreen plant common in both forests and gardens in the Caribbean.

After combing the literature, I found that Mattingly’s anecdote remained the only publication on the species’ egg-laying behavior. Modern phylogenetic analyses corroborate that Micraedes is firmly nested within Culex, not a separate lineage. What Mattingly described could not be dismissed as taxonomic misplacement. Like him, I was perplexed.

To record Cx. antillummagnorum laying eggs in the field, I went to Puerto Rico’s Luquillo Experimental Forest, where larvae had been previously found in phytotelmata (small pools of water that collect in plants). I surveyed Heliconia throughout the forest, searching for patches of sunlight where the flowers grow in broad-leafed clumps. I collected Cx. antillummagnorum specimens in vials and recorded environmental variables at each site.

Three weeks before my flight home, with eggs and larvae but no concrete observations, I worried that my methodology was fatally flawed in some way, that I had failed. After a month of unsuccessful daily treks to sampling locations, I instead began hiking out at dusk, night after night, to sit and observe the same cluster of Heliconia inflorescences. This cluster was adjacent to an old, partially buried, concrete septic tank that served as a daytime resting spot for female mosquitoes. Shortly after dusk, a buzzing cloud of mosquitoes would emerge from the small opening of the tank and fly toward the nearby Heliconia.

With my headlamp fixed on the bracts, I captured dozens of videos of Cx. antillummagnorum laying eggs. Just as Mattingly had predicted half a century earlier, females flew in bouncing, elliptical loops—like a Toxorhynchites—while flicking single, oval eggs into the water, before flying to another bract to repeat the sequence.

These videos, along with detailed descriptions of the behavior, were published in August in Scientific Reports. Also included in the article is the recording of an entirely new egg-laying method not just in Culex but in any known mosquito species. We call it “barrage oviposition”: females perch just above the water’s surface and fire eggs directly from the abdomen into the bract below.

The discovery of Cx. antillummagnorum‘s unusual egg-laying behavior reveals how much of mosquito biology is still a mystery, especially beyond the handful of well-studied species. By paying attention to overlooked species, mosquitoes or otherwise, we can uncover surprising adaptations that may upend long-standing assumptions about entire groups. Future studies should extend research attention to these species. Ideally, this would not only expand our understanding of biodiversity but also, to be optimistic, help us resist collapsing ecological complexity into easy categories.

Liz Wynne, B.S., is a research technician at the University of Southern Mississippi in Hattiesburg, Mississippi. Email: [email protected].