Ditching flowers and chocolates as gifts for China's "Valentine's Day," some lovers have instead gone online to buy insects glowing in the dark.

Fireflies are widely available on the country's booming e-trade sites, marketed as symbols of love and beauty.

The trend is igniting anger among conservationists, who say the business is harming China's already dwindling firefly population.

Online firefly sales traditionally jump ahead of the Qixi festival, also known as China's Valentine's Day. It falls on the seventh day of the seventh month of the Chinese calendar - this year on Thursday.

The number of fireflies traded online so far in 2015 has exceeded 10 million, a tenfold increase compared with the same period last year, a report by Qinghuan Volunteer Service Centre, an environmental protection group, revealed.

More than 30 shops on Taobao.com advertise live fireflies, with prices starting from 3 yuan ($0.5) per insect.

Jars of 55 fireflies, supposedly meaning "I love you," were part of promotions ahead of Qixi. With many of the insects not surviving shipping, extra fireflies are often added to the sets for free.

Glowing mating process

A chemical reaction inside the fireflies' bodies allow them to light up. They glow to lure prey, discourage predators, and most importantly, to attract mates.

Fu Xinhua, a professor at Huazhong Agricultural University, warned that by disrupting this process, fireflies in China could go extinct.

"Firefly adults will appear only one month per year and their life span is about one week," Fu told Al Jazeera.

"If we capture them during their most important stage, there will be no next generations."

He said firefly populations in China are decreasing "very quickly".

Urban development is threatening firefly habitats, and light pollution in the cities is severely disrupting mating.

Firefly populations are also dwindling in the countryside, due to the use of pesticides and pollution.

In mountain areas, where fireflies have been "hiding," they are now under threat of being captured and sold, Fu said.

Exhibits stopped

To promote the business as sustainable, many online sellers claim their fireflies are bred in captivity. But experts say the low price of the insects gives away that they are actually captured in the wild.

Zhou Canying, director of the Changsha Wildlife Conservation Association, told the Global Times Sunday that the cost of breeding each firefly ranges from 15 to 20 yuan ($2.3-3.1), compared to 0.5 yuan each for each insect caught in the wild.

It is not only online sales of fireflies that are controversial.

A firefly exhibit at a theme park in Hunan Province's capital city Changsha was stopped last week after authorities found that it illegally captured fireflies in the wild.

Another exhibit set to open in July in Shanghai, featuring thousands of live fireflies, was cancelled after an online petition and warnings from environmentalists that it could lead to ecological damage.

Such displays are hugely popular among Chinese, who flock to firefly-viewing events during the summer months.

Fu said fireflies are indicators of ecological balance, as they live and breed in areas also healthy for humans.

"If they disappear, our ecosystem will fall apart," he warned.

Qixi celebrates an ancient legend of the love story between a cowherd and a weaver girl.

Traditional celebrations include young women demonstrating domestic skills such as threading a needle and carving fruits.

But many urban Chinese have abandoned these kind of events, instead going to restaurants or cinemas.