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Canadian backyards are glowing this summer.

Across Southeastern Ontario there have been numerous reports on social media of higher-than-usual firefly numbers, ranging from Ottawa to London, Ont. While no formal tracking system can confirm the uptick, experts say it may be linked to a damp and rainy spring, which would have increased slug and worm populations – a larval firefly’s favourite food.

The luminous insects spend almost two years underground as larvae, before the final weeks of their lives when they grow wings, flashing their bright green abdomens in search of a mate – typically in June and July.

“Since there was more food for the firefly [larvae], they were able to survive in higher numbers,” said Aaron Fairweather, an entomologist at the University of Guelph, who prefers the gender-neutral pronoun “they." “As we see them becoming adults now, there’s just a lot more of them than in previous years when it’s been a lot drier.”

The surge in firefly sightings is encouraging to scientists who have seen their population fluctuate.

“We haven’t collected data long enough to know for sure that they’re disappearing,” said Don Salvatore, co-founder of Firefly Watch, an organization that tracks firefly sightings in the United States and Canada. “But you just look and you see fireflies in fewer and fewer places.”

The theory makes sense, because fireflies are affected by light pollution and many prefer to live in marshes, a type of habitat that’s often infringed upon by human development, Mr. Salvatore said. As cities expand, and illuminate the night sky, it could interfere with the fireflies’ ability to communicate with each other.

Part of the reason there are so many unknowns when it comes to fireflies, is they aren’t a popular research subject, said Hume Douglas, a beetle expert and research scientist who works for the Canadian government.

“The question of ‘Are fireflies disappearing?’ is an important one and nobody, to my knowledge, really is working on it in a systematic way,” he said.

Governments and private companies are less likely to fund research into fireflies because the insects aren’t seen as an important pest by farmers and it’s unclear what critical role they play in the ecosystem, Dr. Douglas said. In 2011, a handful of researchers published one of the few North American papers about fireflies: The Fireflies of Ontario. During the course of their research, they discovered six species not previously recorded in Ontario.

“[The new species] weren’t rare or uncommon, they were common species that we just didn’t know anything about because nobody had looked for them before in Canada,” Fairweather said. “You’d think these insects would get more attention because they are so beautiful and charismatic.”

Soon, Mr. Salvatore hopes to train Firefly Watch volunteers to differentiate species of fireflies by their unique flash patterns.

Fireflies use their bioluminescence for communication; they flash when they’re looking for a mate. Their light also serves as a warning to deter potential predators.

Mr. Salvatore wants to help understand which species are more widespread and how they’re affected by climate, temperature, light pollution and other factors.

For Kristen Ungar, that would be a good thing. She’s noticed hundreds of the insects in her backyard in London, Ont., this summer. So many, they look like flickering stars. Like many Canadians, she remembers them from her childhood but hasn’t seen many in recent years.

“I remember it being a rare sighting,” she said. "But this summer I can just open up onto my backyard and there’s all these glimmering lights.”

To Fairweather, the luminous beetles have a sense of wonder about them that makes them more interesting than other bugs to the average person. They warned, though, that while this year may have been a good one for fireflies in some parts of North America, the species is vulnerable to human behaviour.

“Maybe in 30 years time, if we keep up the same habits we have now, our kids or our kids’ kids might not see the beautiful flickering lights that we see in our back fields," they said.

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