Fossilised mosquitoes suggest male mozzies also once sucked blood

Fossilised mosquitoes suggest male mozzies also once sucked blood

It is a fact often trotted out at summer barbecues when mosquitoes are buzzing around — only female mozzies drink blood.

The modern male mozzie doesn't have the mouthparts to cause those irritating — and potentially very dangerous — itchy bites.

But that was not always the case, according to new research.

Closer inspection of two 130-year-old male mosquitoes fossilised in amber has revealed that they too had the mouthparts to suck blood.

What is the difference between male and female mosquitoes?

Female mosquitoes drink blood and live for about a month.

Male mosquitoes feed on nectar and only live for about a week.

Males have bushier antennae than females, which the CSIRO says helps them detect the scent and specific wing beats of females.

You can see that difference in this CSIRO image of a mozzie species called Aedes aegypti below, with a male on the left and a female on the right.

A male mosquito with a set of fluffy antennae and a female, with less hairs on her antennae. Both have long mouth parts
Male mosquitoes have bushier antennae than their female counterparts. (Supplied: CSRIO)

You can see they both have a proboscis — which is a word used to describe the long, straw-like biting organ attached to their heads.

But the females have more of a "needle-like" proboscis than males, as demonstrated in this image from a Singaporean government fact sheet:

Close up images of a male mosquito proboscis, which has a moustache-like appendage compared to a needle-like female proboscis
Here is a close-up demonstrating the differences between male and female mosquitoes.(Singapore Ministry of Health)

So what is different about the old mozzies?

The two mosquitoes that were the subject of the study are the earliest-known preserved mosquitoes, but the specific species is now extinct.

They are similar to modern mosquitoes, though the mouthparts are shorter than those of today's female mosquitoes.

These mosquitoes were found in amber discovered in central Lebanon.

Because the fossilised amber perfectly preserved their bodies, experts were able to zoom in on their "exceptionally sharp", serrated mouthparts.

They weren't expecting that.

A close up of a mosquito head in a yellow substance.
In the report, the mosquitoes' mouthparts are described as "piercing" and "exceptionally sharp".(Reuters: Dany Azar/Supplied by third party)

Researchers, led by palaeontologist Dany Azar of the Chinese Academy of Sciences' Nanjing Institute of Geology and Paleontology, say these "piercing" parts suggest these male mosquitoes sucked blood.

"Such behaviour would be surprising for a male mosquito, given that the extant males feed on nectar, plant sap, or honeydew," they wrote.

It's thought that hematophagy — which means feeding on blood — in modern insects came about in a shift from "plant sucking to bloodsucking", Dr Azar said.

But these results suggest that originally the first mosquitoes all sucked blood, no matter their sex.

Do male mosquitoes bite people?

No — well, not the modern ones.

However, the 130-million-year-old mosquitoes used in the amber study wouldn't have bitten people either … because human beings weren't around back then.

Because modern male mosquitoes don't bite, they don't transmit disease like females do.

Why do only female mosquitoes suck blood?

"They need proteins to make their eggs develop," Dr Azar said.

Before they're fertilised, they'll eat nectar like males do.

"A few days after a blood meal, female mosquitoes lay about 200 eggs on any water surface — even small water bodies such as bottom trays of potplants are suitable," an Australian Museum fact sheet says.

"Most species produce egg 'rafts' where many eggs are cemented together, floating until they hatch after two to three days."

A female Aedes aegypti mosquito
A female Aedes aegypti mosquito sucks blood from a human. (AP)

Why did males lose the ability to suck blood?

"A reason for why this behaviour was subsequently lost in males remains unknown," the report said.

But experts have their theories.

Dr Azar says it might have been due to the emergence of flowering plants offering alternative food sources.

Research from the University of Melbourne two years ago showed that male mosquitoes were still attracted to people.

However, because males aren't trying to feast on blood, researchers suggest they swarm to people because they know that's where the females hang out — and they're looking to reproduce.

Why do mosquitoes flock to some people?

There are a few theories, such as a person's diet, their temperature or how active they've been.

Research from last year suggests it could have something to do with people's smells.

A study found mosquitoes were drawn to people who secrete an odour on their skin caused by a mix of naturally occurring acids.

The study tested human forearm odour and was able to identify "people who are exceptionally attractive or unattractive to mosquitoes".

Those who were attractive to mosquitoes had higher levels of carboxylic acids in their skin, with researchers suggesting this came down to genetics.

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15th Dec 2023 Dannielle Maguire with wires. ABC News

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