Oldest mosquito fossils upend blood-sucking evolution theory

Two mosquito fossils, preserved in Lebanese amber, are challenging scientists’ understanding about how blood feeding developed in the insects.

Scientists have described two fossilised male mosquitoes, well-kept in Lebanese amber from the early-Cretaceous (a period lasting from about 145 million years ago to 100 million years ago), publishing their findings in Current Biology.

The fossils are significant for two reasons: their age, and their mouthparts.

Based on molecular dating, scientists believe mosquitoes date back to the Jurassic, about 197.5 million years ago. 

However, the early fossil record is sparse. Previously, the earliest mosquito fossil was from the mid-Cretaceous. This makes the newly-described mosquito fossils (from the genus Libanoculex) the oldest known specimens, some 30 million years earlier.

Also significant is the unexpected presence of piercing-sucking mouthparts in the fossilised specimens, suggesting these males were likely blood feeders. That’s important because modern male mosquitos don’t drink blood, they mostly feed on nectar. 

Blood sucking was previously thought to arise as a shift from nectar feeding in the insects. But the revelation that male mosquitoes fed on blood in the past suggests the evolution of feeding behaviours may be more complicated.

While only female mosquitoes today feed on blood, both males and females are known to feed on nectar.

The authors write: “The benefit for Cretaceous male mosquitoes to feed on blood could have been to increase their capacity to fly and successfully mate, as is the case in extant females, but a reason for why this behavior was subsequently lost in males remains unknown.”

Amber from Lebanon was formed in the early Cretaceous, under an equatorial tropical forest in northeastern Gondwana. According to the paper, discoveries in the amber often represent “missing links” between the Jurassic and later flora and fauna.

“Lebanese amber is, to date, the oldest amber with intensive biological inclusions, and it is a very important material as its formation is contemporaneous with the appearance and beginning of radiation of flowering plants, with all what follows of co-evolution between pollinators and flowering plants,” says author Dany Azar of the Nanjing Institute of Geology and Palaeontology at the Chinese Academy of Sciences and the Lebanese University.