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Researchers look at how fog affects mosquitoes
Josh Pennell - The Telegram
Campers take note: When the fog is thick the flies are down. That's the preliminary findings of Tom Chapman, an entomologist at Memorial University.

With the help of two student researchers - master's student, Andrew Chaulk and honours student Miles Fielden - Chapman is looking at how the weather event that grounds so many flights in the capital city also affects that black mark on any camping expedition - the mosquito.

The idea to look at the behaviour came about when another of Chapman's students found an interesting YouTube video that showed a research group in the United States looking at how raindrops affect the flight of a mosquito.

"I think anyone including that group would have thought that mosquitoes would have been knocked out of the air by something so large compared to their body size," says Chapman.

Not so. The slowed-down video shows a mosquito flying through a narrow tank as artificially made raindrops fall from above.

"The droplet will come into contact with the mosquito and the mosquito will go right into the droplet and might drop with the droplet only a few centimeters and then come right out of it," says Chapman.

"So it's really fascinating."

Another video out of the Georgia Institute of Technology, where researchers had mosquitoes flying through a chamber full of homemade fog got Chapman thinking.

"How much fog do they get in Georgia? Maybe more than I think, but it can't be as much as we get here," he muses.

Chapman and his students started to wonder how the weather - specifically the prevalence of fog - might affect mosquito numbers and variety in different parts of the province.

As horrific as it sounds, there are actually more than 30 species of mosquitoes in the province, but before anybody duct tapes the ends of their clothes shut, keep in mind that they're not all out for human blood. The females of the species are the only ones that bite because they need a blood meal to produce eggs and only some target mammals.

The researchers needed mosquitoes and they needed fog, a task not as easy as it sounds despite the abundance of both in the immediate vicinity.

Chaulk says they collected standing water from different locales that had mosquito eggs, larvae and pupae. That's the order of the life cycle the fly goes through and from the pupae stage comes the adult.

In various samples in their lab, different species of mosquito are maturing. They also collected adult samples through various traps and nets. So with a kind of mosquito farm going, they needed the fog and collecting that wasn't an option. It had to be made.

Using a humidifier and a glass chamber, they were able to recreate the setup they saw on YouTube.

"Our lab, because of the exposure to the sun, can heat up quite a bit so our fog was getting thinner. So we moved the setup into a beer fridge," says Chapman.

So they had the mosquitoes, they had the poor weather and they had the beer fridge. The mad camping experiment was all set. They're still accumulating data at the moment, but one thing is clear.

"What we can say definitively is that in heavy fog, we haven't found a mosquito that can fly in it," says Chapman.

As soon as a mosquito is put in the fog chamber, it drops right to the bottom. The team is working on a protocol whereby they let the fog they've created dissipate and watch how the mosquito recovers.

As odd as scientists can sometimes be, this crowd isn't deranged enough to be locked away in their lab all summer hatching mosquitoes and making fog just because they've figured out they can. There is a method to their madness. Using a humidifier and a beer fridge, they're actually looking at a bigger picture of how the movement and abundance of certain species of mosquitoes could affect people's health.

Chapman says one species known to carry the West Nile virus - Culex Pipiens - was known to be on the west coast of the island for some time, but it was thought conditions on the Avalon were too dry for that species. That's an assumption that Chapman and his team have proven wrong.

"We're finding it here. So we're wondering if it's just an accident where we have the conditions one year where we're getting them and the next year we're not," says Chapman.

"We want to know that to assess the health risks for the people in the most populace part of the island."

Determining how well that species is established in various parts of the island has become a moving target due to climate change, says Chapman, and looking at how they exist in fog is one way of determining its prevalence in different parts of the province.

"So the fog thing is silly in one regard. I think that's why it's going to attract attention, but it's serious in the other which (asks) are foggy areas going to have different propensities for hosting these vectors than other parts of the island."

As for why the mosquitoes can fly through raindrops but not fog, there are already two lines of thought.

Chapman says the group out of Georgia thinks the fog might affect sensors on the mosquitoes used for keeping track of body orientation. He and his team are thinking it might have to do with the surface structures of the flies that might collect condensation quickly in fog.

Mosquitoes are covered in hairs. The males have feathery antennae that could trap more moisture and there are also differences in structures between species.

"So one of our predictions is that males will have more difficulty in the fog than females," says Chapman.

They're hoping to have some definitive answers by Christmas. In the meantime, they're well aware that making fog and hatching mosquitoes is setting them up for a few jokes. Chaulk has already felt the sting of humour that could match the bite of any of the mosquitoes he's fathering in the lab.

"When we had the guys building the fog chamber, one looked at me and said 'why do you need this?' And I told them and he said 'so you're definitely from town, right? Leave it to a townie to find a use for all the fog.'"

Jul 4th, 2013

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