Wet springs in the Yukon are usually followed by bug-filled summers, making dragonflies a welcome sight. These tiny, jewel-like helicopters of the insect world are voracious predators, eating plenty of mosquitoes and midges as well as yellowjackets and even smaller dragonflies.

The Yukon's 33 species of dragonflies come in a range of vivid colours, from the cherry-faced meadowhawk with its bright scarlet body and face to the whitefaces with their chalky heads and black bodies covered in red or yellow spots.

But despite popular conception they're not the most efficient mosquito predator, says entomologist Syd Cannings of the B.C. Ministry of Sustainable Resource Management's Conservation Data Centre in Victoria.

"When dragonflies are really common, between 10 a.m. and two p.m. on sunny days, mosquitoes are hiding in the bushes. And when mosquitoes come out at suppertime, dragonflies are going into the bushes to go to bed, so they don't overlap a lot in their daily routines."

However, it's not only the adult dragonflies who prey on mosquitoes but also the developing larvae, which hatch out of the eggs within one to three weeks. Dragonfly larvae take up to six years to mature, depending on the species, and will go through 12 or 13 stages of development during that time, moulting or shedding their outer casings at each stage.

And during all this time they are feeding on the larvae of smaller insects, including mosquitoes.

In the Yukon, dragonfly larvae have developed the ability to overwinter in frozen ponds because of special antifreeze in their bodies.

"Dragonflies by and large are a tropical group, so what you're seeing are a very odd bunch here that can live up north," says Cannings.

Cannings carried out research into Yukon dragonflies during the 1980s as part of a team sponsored by the Biological Survey of Canada to do an insect survey of the Yukon.

"I'm standing on permafrost two or three feet beneath the surface of a timberline pond in the Richardson Mountains, and there are larvae emerging as adults out of the moss over my toes that have been there for five years," explains Cannings.

During the winter larval metabolism slows down so much they don't need to feed, but they resume their growth in spring, using daylight and body size as cues to tell them when to shed their skins. In the Yukon the first adult dragonflies, such as the subarctic bluet, the taiga bluet, and the four-spotted skimmer, emerge during the first warm days at the end of May.

By mid to late June the ringed emeralds and the Hudsonian emeralds emerge, followed by the biggest dragonflies -- the blue darners -- at the height of summer in July.

"Then they come out in great numbers, and when people say 'Wow, all of a sudden there's lots of dragonflies around,' it really means there's lots of darners around," says Cannings.

In fact, if you're standing at a pond and seeing hundreds of dragonflies, 95 percent of them are males, hanging around the waterholes looking to mate. A female may choose not to accept a male, but if she does they will spend up to an hour linked together in the trees, where the male will spend most of that time removing all the sperm deposited in her genital tract by other males.

Male meadowhawks will even hover beside the female as she lays her eggs to make sure nobody else mates with her. Perhaps that fierce competition is due to their short lifespan, with the whitefaces dying off by late July and the darners lasting until the first September frosts.

"They have a much longer life as larvae than as adults," says Cannings, who's travelled as far north as Herschel Island looking for dragonflies.

Although he found no larvae, "there were certainly adults there, so they do have the ability to travel long distances," says Cannings. One of his favourites is the treeline emerald, first discovered almost 100 years ago in Finland but since largely unknown in Europe.

" We found it at Old Crow and along the Dempster Highway in the Ogilvie River valley -- it's one of the common dragonflies there, a far northwest specialty," says Cannings.

The treeline emerald is named for its brilliant green eyes, which like those of other dragonflies have up to 30,000 facets, giving them excellent vision as well as the ability to see in colour.

"They're looking for mates and they're using their eyes, just like we would, so they live in this visual world that we can appreciate," says Cannings.

Perhaps that's why dragonfly watching is one of the fastest growing hobbies among natural history buffs in North America and Europe. A whole world, Cannings points out, is being enacted around a pond, where "territories are set up and defended and lost, and everything happens in one day."