Everyone has their own experience, but I found a wide variety of mosquitoes in Alaska when I was there a couple of years ago. It's not that they were big, but in lots of areas they were just so thick that you could hardly breathe without sucking them in. A mosquito head net was invaluable for me. Once in a while we were in a area where there were remarkably few mosquitoes. Someone posited that it depended on when the little monsters hatched.
In Wiseman, just north of Coldfoot, I woke one morning about 4:00 a.m. In the middle of the summer, the sun was shining brightly and the temperatures were moderate. It was stunningly beautiful...except that the mosquitoes were so thick that someone not used to them (me) found it to be almost impossible to stay outside.
Regarding Canadian maps for your GPS, I agree with DirtFlier...don't leave home without them. My old GPS is somewhat limited in its capacity for holding the current map sets, so I'll have to load the eastern half of the US and Canada or some other partial option. Then again, maybe that's another reason to have multiple GPS units...I can have different map sets loaded on each one.