bit of science

Today, Prof. Leslie Vosshall from the Laboratory of Neurogenetics and Behavior at Rockefeller University stopped by Imperial to give a talk on mosquitoes, sweat and smell. It wasn't the first time that mosquitoes had taken center stage. There is in fact a solid research effort going on in house. The world's first transgenic malaria mosquito was created at Imperial and work is underway to genetically manipulate mosquitoes to render them immune to the parasite that causes malaria in humans. It's science fiction stuff.

Leslie Vosshall's talk was more exploration than science fiction. She discovered the receptors that allow insects to react to smell and taste (A member of the same family of receptors is responsive to UV radiation – these bugs can smell light.) and is now working to design inhibitors to confuse insects or maybe even actively repel them. The gold standard in insect repellents is DEET, which does the job but you need a lot and apply it frequently. Her inhibitors, pharmaceuticals with a new career perspective, aren't quite up to the task yet but show promise.

Repelling insects is only one side of the story. The other is the question of how insects identify their victims. It turns out that they are very picky. They don't just bite anyone. He or she has to smell good from a distance and then taste good when the insect's proboscis scans the human surface it has landed on.

Back in the fall of 2000, when I traveled Mexico's Pacific coast with my sister, I realized this clearly. After seeing the spectacular little island of Mexcaltitán – two pairs of parallel roads that intersected at a square half a meter higher than the surrounding sea – we drove to San Blas to spend the night. According to my Moon Guide, San Blas was the gateway to tropical mangrove marshes, tunnels of lush vegetation alive with orchids, egrets, turtles and fish. This we wanted to see the next day, but first we had to survive another dweller of the mangroves, the invisible biting gnat that comes out at night in large swarms and terrorizes the town.

For the sake of scientific accuracy, it's worth mentioning that the guidebook's gnats were in fact Phlebotomus, sandflies also known as jejenes. Neither gnats nor sandflies are mosquitoes, but the bites hurt the same and the physiology is probably similar given that all three of them are diptera, insects with two pairs of wings.

We went to bed with apprehension. The room in the little guest house we were staying at were grouped around a central courtyard and open to most of the elements. The windows didn't close properly – nor would we have wanted to close them given the heat that burned through the night. There was no air conditioning and the ceiling fan whirled only feebly.

The next morning I awoke, stretched myself, rolled from one side to the other and patted my arms to check for damage. There was nothing. I woke my sister; the jungle beckoned: "I don't know what they're talking about. There's no mosquitoes here." "Oh, shut up," she replied with suffering in her voice. "I'm bitten to pieces." The mosquitoes has feasted on her all night, while I got away unscathed.

How to explain that? That's something Leslie Vosshall is also interested in. What constitutes the smells they're attracted to? Epidermal bacteria, body odor, components of the sweat? If you're in New York, give them a ring and they'll let you stick a hand into a long tubular contraption full of mosquitoes. With this, they'll count the percentage of bugs that find you attractive. I'd love to give it a try – in the hope of setting a new global low and help science in the process.