Many Yukoners figure that they know all that they need to know about insects in the territory. They bite and swarm. The first wave of mosquitoes attacks in June and black flies take their turn in August.

But there is much more to appreciate about the bugs in this part of the world. The Yukon has a surprisingly diverse and interesting population of insects for such a northern area. And enough is now known about them to fill a book that weighs in at about two kilograms.

"Insects of the Yukon," published in 1997 by the Biological Survey of Canada, is the largest publication to date ever put out by this organization. More than a thousand pages long, the book reflects 20 years worth of research, and brings together information on more than 2700 species of insects. They include 913 species of beetles, 297 species of spiders, 159 species of mites and 88 species of butterflies.

The Survey chose the Yukon as the first area for an extensive study of the insect population because less was known about insects here than of any other major region of Canada. And Yukon insects also give clues to how animals dispersed over North American and Asia after the end of the last Ice Age.

"About 10% of the insects of the Yukon are Beringian survivors," says H.V. Danks, a co-editor of the book.

Beringia once stretched from eastern Siberia across Alaska and the northern Yukon. This northern region was never covered by glaciers during the last Ice Age, so it served as a refuge for many species of plants, animals and insects.

The Beringian insects never dispersed to other areas even after the ice sheets melted. They refined their abilities to cope with arctic conditions, often in interesting ways. For example, the Yukon has a relatively large number of insects that have reduced wings but don't fly. Six types of butterflies have been identified in the northern Yukon with this characteristic.

Danks, an entomologist with the Canadian Museum of Nature, says this adaptation could have occurred because there was no place better to which these bugs could fly. By reducing their wings the insects could save energy and use it for other priorities -- like making eggs.

Another adaptation involves our endearing biting insects. About 25% of Yukon black flies and some of our mosquitoes are "autogenous," meaning they don't feed on blood. These insects probably evolved away from the biting habit during the long periods when there was not much on which to feed.

Instead these high-latitude vegetarians filter food out of the water while still in their larval stages. Female blackflies can use this stored food later in life to produce eggs, while blood-feeders are not capable of building up such reserves.

Only 3% of the blackflies in the rest of Canada have this habit. And rest assured. The autogenous blackflies cannot suddenly change their menus if you happen to wander into range. Their mouth parts are not capable of cutting through flesh.

But there is always a balance in nature, and we have our short northern summers to thank for the clouds of biting insects that can be the bane of northerners. Insects tend to emerge rapidly and en masse early in the summer here since they have little time in which to feed, reproduce and lay eggs.

Danks says that the next time we're swatting at a swarm of mosquitoes, we should remember that they are one of the linchpins for all life in the north. Insects are the main food source for northern fishes. They also give young birds a huge boost.

"These clouds of insects, particularly midges, are the reason that many migrating birds go north," he says. This abundant food supply helps the chicks develop rapidly. Even some vegetarian birds such as ducks eat insects when they are young.

Surprisingly enough, there is only one passing reference to Culicidae, the family that includes mosquitoes, in the entire book. Even though most Yukoners would no doubt put mosquitoes at the top of their lists of obvious Yukon insects, no expert chose to focus on this particular family of insects.

Many Yukon insects have not even been identified yet. Danks figures that the species list could double in size as more research is done. But even now, the number of Yukon insect species outnumbers the total number of Canadian mammal species by a factor of 30 to one.

Danks says we can gain a great deal of practical knowledge by studying insects. They are sensitive to changes in the environment, and can tell us more about how ecosystems work.

He favours more of a "bottom-up" approach to resource management, rather than always looking at the animals at the top of the food chain. "It doesn't work to manage only for bears," he says, "and then hope that everything else will be okay.

"Studying insects gives you the ability to find things out in detail. You have a wide variety of beasts doing a wide variety of things. If you're interested in a particular area of study, somewhere there will be an insect doing something in that area."

If the $95 price tag on Insects of the Yukon puts it out of range of your budget, you can always borrow it at the Whitehorse library. Winter can be the perfect season to contemplate the finer points of Yukon insects, knowing that they're all safely dormant for another few months.

For more information on Yukon insects, you can contact H.V. Danks at the Canadian Museum of Nature by e-mail at hdanks@mus-nature.ca.