Female mosquitoes have strong proboscises that can puncture the skin of animals, allowing the insects to suck their blood. Male mosquitoes, on the other hand, do not—with their weaker mouth anatomy, they only feed on plant juices.
But in a study published Monday in the journal Current Biology, researchers report finding two prehistoric male mosquitoes, trapped in amber, with piercing mouthparts similar to those of modern females. The findings suggest that male mosquitoes may have once fed on animal blood, too.
“Clearly they were hematophagous,” or blood-feeders, lead author Dany Azar, a paleontologist at the Nanjing Institute of Geology and Paleontology in China and Lebanese University, tells Reuters’ Will Dunham. “This discovery is a major one in the evolutionary history of mosquitoes.”
The theory that male mosquitoes were bloodsuckers long ago is “interesting and fascinating and controversial,” Dale Greenwalt, a paleobiologist at the Smithsonian’s National Museum of Natural History who did not contribute to the findings, tells the New York Times’ Kate Golembiewski.
Today, both male and female mosquitoes eat flower nectar and fruit juices. But females also need to drink protein-rich blood to produce eggs.
Researchers have theorized that blood-sucking insects like mosquitoes and fleas used to eat only plant fluids, before they shifted to blood. But a lack of insect fossils from that period makes it difficult to pin down when and why the animals may have added blood to their diets, the study authors write.
For the new study, the researchers looked at two male mosquitoes preserved in amber from Lebanon that date to the early Cretaceous epoch, which lasted from around 100 million to 145 million years ago. These are the oldest known fossils of mosquitoes, and the species is thought to date back to the Jurassic period, between around 146 million and 200 million years ago.
Azar first collected the amber specimen containing the mosquitoes some 15 years ago, but he didn’t look at them until more recently, per the New York Times. Examining the prehistoric insects revealed they had sharp, triangular mandibles and elongated structures with small, tooth-like projections, according to a press release. These parts suggest the two mosquitoes fed on blood.
The finding “means that originally the first mosquitoes were all hematophagous—no matter whether they were males or females—and hematophagy was later lost in males, maybe due to the appearance of flowering plants, which are contemporaneous with the formation of Lebanese amber,” Azar tells Reuters.
The researchers write in the study that male mosquitoes could have fed on blood during the early Cretaceous to make them better fliers and more likely to successfully mate, but if so, it’s unclear why they stopped this behavior.
The New York Times notes that it’s possible that the two insects in the study are actually not mosquitoes, or that they didn’t use their sharp mouths to suck blood.
Fossils in recently discovered outcrops of amber from Lebanon that hardened during the early Cretaceous can help scientists to better understand biodiversity during this time, the study authors write.