Encased in a cage of golden amber appears a prehistoric mosquito, completely intact, as if about to spread its wings and take to the skies. This insect died some hundreds of millions of years ago, trapped in the amber that preserved it. On Dec. 5, palaeontologist and geologist Dany Azar announced the discovery of this mosquito, marking a major development as it is the oldest to date. The fossilised specimen belongs to a sub-family that has never been identified before, and its characteristics provide new insights into the evolution of insects.

The story began around fifteen years ago when Azar found two specimens of mosquitoes and many other insects trapped in amber in the Hammana region. "At first, we thought they belonged to another insect family, the Chaoboridae (a family of Diptera in the Culicoidea superfamily, to which mosquitoes also belong)," he explained. As they were not initially considered a priority, it took some time before these two specimens were selected, cleaned, cut, polished, mounted between two slides and studied under the microscope.

"That's when we realized that they were mosquitoes and not chaoborids," continued Azar. This new species has been identified for the first time and only in Lebanon hence its new name, Libanoculex.

When males stung

This momentous discovery is the subject of a scientific article in the journal "Current Biology", recently published by the Lebanese palaeontologist and other French, Chinese and American researchers.

It is a remarkable discovery for various reasons, the first being “the age of these fossils, which we have been able to date at around 130 million years. Until then, the oldest mosquito fossils had been discovered in Burma, and dated at 99 million years," explained Azar.

The other surprising finding came from studying the specific characteristics of these male insects. "In modern mosquitoes, it is only the female that bites, particularly when she is fertilized, because she needs the proteins contained in the blood to develop her eggs," Azar noted. However, these two Cretaceous specimens have characteristics that have never been seen in male mosquitoes: haematophagous mouthparts, i.e. hard, pointed structures with lots of small denticles that are used to pierce the skin. This is very intriguing and surprising in terms of the evolutionary history of insects," he commented. It means that these insects were essentially haematophagous, both male and female and that they abandoned this source of food in the course of their evolution.

Plants, more nutritious than blood

So why did these 130 million-year-old male mosquitoes drink the blood of other living creatures? Part of the answer can be found in the environment of their time. The Lower Cretaceous period saw the appearance of flowering plants, a major ecological evolution. "We might say that, with the arrival of new sources of food, these insects gave up feeding on the blood of others," he explained. The life of a haematophagous insect is not an easy one: it risks a great deal by getting close to creatures much larger than itself. Not to mention the fact that blood is mainly a source of protein, and it takes a lot of energy to extract nutrients from it. Plants, on the other hand, are a safer and quicker source of energy, consisting mainly of nectars and sugars.

"We hope to find more specimens of this same subfamily, preferably females so that we can complete our study," said Azar.

Lebanese amber, linked to flowering plants

The significance of this discovery highlights the unique characteristics of Lebanese amber, one of the oldest in the world, dating back to the era of flowering plants. "A lot of researchers go to Burma to study amber, but ours is older and the deposits richer because of the tropical climate that prevailed at that time in the north-east of Gondwana (the ancient supercontinent), on the shores of the palaeo-ocean Tethys," said Azar. "The proof is that to date we have been able to identify more than 400 species in less than five kilos of amber!”

However, he deplored the lack of regional stability, which is detrimental to the study of the country's remarkable scientific potential. "When the southern front opened up following the outbreak of war between Israel and Gaza in October, we had scheduled an international expedition to excavate fossils in the Jezzine region. Although its work proved to be very fruitful and will give rise to at least twenty scientific publications, the experts had to leave the country in a hurry. It's a shame... "