Millions of years ago, male mosquitoes may have been blood suckers too

Male descendants of the insects do not have the mouthparts strong enough to pierce skin.
A mosquito encased in yellow-hued amber.
A mosquito encased in amber. Deposits of this tree resin can provide clues into insects and flowering plants co-evolved over time. Dany Azar

If you’ve ever been bitten by a mosquito, it was a female insect that chomped on your skin. Female mosquitoes are hematophagous, which means that they feast on animal blood. They then use the blood to produce their eggs. Male mosquitoes living today are not hematophagous. Instead, they survive on plant nectar because their piercing mouthparts–the proboscis–aren’t strong enough to pierce skin.

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However, male mosquitoes may have been blood suckers hundreds of millions of years ago. A team of paleontologists found two male mosquito fossils from the Lower Cretaceous period with intact piercing proboscis and sharp mandibles needed to suck blood. The specimens are described in a study published December 4 in the journal Current Biology and help to narrow a “ghost-lineage gap” for mosquitoes.

Hematophagy is the ability for insects to suck on the blood of other animals. It’s believed to have evolved from a shift to using piercing-sucking mouthparts to extract fluids from plants instead of animals. Fleas that currently suck animal blood possibly arose from earlier species of the insects that primarily fed on plant nectar. The evolution of hematophagy has been more difficult to trace, partially due to gaps in the insect fossil record.

The fossils examined for this study were found preserved in amber in Lebanon and date back about 130 to 125 million years. Amber is a fossilized tree resin and deposits in Lebanon are some of the oldest known amber samples that contain traces of living things including insects. Studying this material can close “ghost-lineage gaps,” or a chain of ancestors that does not usually appear in the fossil record. Coelacanths are a famous example of a ghost-lineage gap. These lobe-finned have a long fossil record from the Devonian to the Cretaceous–or a period of about 300 million years. However, they were not found in sediments younger than the Cretaceous, so scientists assumed that they had been extinct 80 million years. A living coelacanth was caught off the coast of South Africa in 1938 and another population lives in Indonesia. Coelacanths have just not left any fossils over the past 80 million years. 

Amber deposits can also offer scientists clues into how pollinating bugs and flowering plants co-evolved over time. The pollinators include some members of the Culicidae family of arthropods which has over 3,000 species of mosquitoes. 

“Molecular dating suggested that the family Culicidae arose during the Jurassic, but previously the oldest record was mid-Cretaceous,” study co-author and entomologist at the National Museum of Natural History of Paris André Nel said in a statement. “Here we have one from the early Cretaceous, about 30 million years before.”

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In the new study, the team describes the fossils of two male mosquitoes from the Cretaceous period that have piercing mouthparts. The parts include a very sharp triangular mandible and elongated structure with small, tooth-like denticles. The presence of these parts suggest that male mosquitoes living during the Late Cretaceous could have been strong enough to pierce the skin and feed on animal blood like their modern female descendents. 

The team also reports that the mosquitoes’ preservation in amber stretches the family tree of insects further back into the Cretaceous period. The fossils also suggest that the evolution of blood-sucking behavior was more complicated than they had previously suspected. According to Nel, the team hopes to investigate why being hematophagous was advantageous to Cretaceous male mosquitoes and why it no longer exists in future studies.