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Mosquitoes are a nuisance because of their buzzing and biting, but they are also the most deadly animals for humans, due to the transmission of different viruses and parasites.

Some species of these flying killing machines feed exclusively on humans, but to be such a successful feeder, they must have evolved precise targeting mechanisms to distinguish between human and animal scents. Now researchers are finally figuring out how they do it.

A new study published in Nature could answer the question: What do mosquitoes detect and how do they detect it?

The team created genetically modified Aedes aegypti mosquitoes, vectors of Zika virus, dengue virus, yellow fever virus, and chikungunya virus, using CRISPR-Cas9. These transgenic insects had brains that lit up when active, allowing scientists to image the brains in high resolution. The researchers then fed human- and animal-scented air to the mosquitoes through a wind tunnel to determine what attracted the insect's attention.

Human odour is made up of many different compounds, and these same compounds are also present in most mammalian odours, but in different proportions. Previous research has found that the compounds alone are not attractive to mosquitoes, so determining the exact ratios of the attractive compounds is a challenge.

The team used the scent of 16 humans, two rats, two guinea pigs, two quail, one sheep and four dogs to stimulate the mosquito's appetite. The way they collected these samples was quite interesting. For the sheep, they had a farm donate several fleeces, and for the dogs, they visited a grooming salon and collected clipped dog hair.

For the human samples, they had a lot of great volunteers according to study author Jessica Zung. They asked them not to bathe for a few days, and then they undressed and lay down in a Teflon bag.

Once they recovered all of these odours, they designed a clever system to inject the genetically modified mosquitoes with odours into the imaging setup area.

The mosquito brain has 60 nerve centres called glomeruli, and the team originally hypothesized that most of these centres would be involved in helping the mosquito find its next meal and distinguish human from animal scents, but it turned out to be all that contrary.

"When I first saw the brain activity, I couldn't believe it, only two glomeruli were involved," said Zhilei Zhao, a member of the research team. "That contradicted everything we expected, so I repeated the experiment several times, with more humans, and more animals. I just couldn't believe it. It's so simple," Zhao added.

Through experiments, it was determined that mosquitoes detect two chemicals (decanal and undecanal), which are enriched by human odour and likely originate from unique human skin lipids rather than sweat.

Overall, this collaborative research can help the development of new repellents, allowing us all to enjoy the nice outside air without the fear of these nasty bugs stealing our blood.

But in the meantime, there is, however, a natural remedy that can keep insects at bay in our home. A basil plant on our window sill will drive away mosquitoes.

On more than one occasion, when looking for a parking space in the street you will have come across a person without a vehicle standing in a space and 'saving' that space for some other car - or maybe that was even you standing there!

This is a situation that tends to generate conflict and many times arguments as to who should occupy the parking space. So where does the law stand with this? Is it legal or not?

The Law on Traffic and Road Safety specifies that "as long as there is a safe area, a pedestrian area or some other suitable space, pedestrians may not remain immobile on a hard shoulder or on a road, not even while waiting for a vehicle, they must remain in this safe area until the vehicle reaches their position."

Therefore, what the law is saying is that this is an action that is not permitted.  Although it is common and many people do it, blocking a site for a friend or family member is not allowed and the vehicle that wants to park can do so legally. The problem arises if the person occupying the parking space is not willing to move away.

The solution may be to call the police, since invading the road or crossing it in an inappropriate manner carries a fine of 80 euros.

Another less frequent 'trick' but also carried out by some people is to park the vehicle incorrectly, occupying two spaces by exceeding the line that delimits each space. In this case, if a person reports what happened, the tow truck can proceed to remove the vehicle and impose a fine of 80 euros up to 200.

Something to think about...

A part of one of the oldest towers in Madrid is nestled among the cars in a nondescript underground car park. Stumbling upon it is a treat for those looking for a place to park before heading to the Royal Palace in Madrid.

The Tower of Bones (la Torre de los Huesos) was built in the 11th century by the area’s Muslim inhabitants. It received its name because it was near Huesa del Raf, the ancient Islamic cemetery. The tower was built two centuries after the 9th-century construction of the walls of Mayrit, the medieval Muslim city that predates the Spanish one.

The looming structure was situated outside the citadel, where it functioned as a surveillance post over the old Arenal stream. When King Alfonso VI of Castile conquered Madrid in the early 11th century, the watchtower was incorporated into the Christian wall.

The Royal Palace now occupies the space the tower was built to guard. Bits of its base were discovered in 1996 during renovation work on the Plaza de Oriente by workers constructing an underground parking lot. The partially preserved remains are on display where they were found.

The carpark is situated in front of the Royal Palace in the heart of Madrid. The nearest tube station is "Opera."