Don't know if it's true or not, but I was told that in Canada bear spray is legal but pepper spray isn't. Bear spray comes in the large cans and pepper spray in the small ones. I did but bear spray last summer in Alaska and never had a problem with border crossings. I always told Canadian Customs I had it when asked and they never asked to see it or to see a receipt. I crossed back and forth going in Haines and Skagway on my return trip and I came back into the Lower 48 thru Montana.
My only "problem" with Canadian Customs is I'm flagged in their database for a work related situation a few years ago that I'd always have to explain. It was never a problem though. However I did notice that US and Canadian Customs are now sharing a lot more information and a couple of times US Customs asked me about the "incident". So whatever your story might be make sure it's the same story you tell on both sides of the border!
I did read someplace that placing a clothes dryer sheet in a shirt pocket can help ward off bugs but I never tried it. Growing up in Alaska I guess I just got used to them, although when it was really needed DEET seemed to work the best. Mosquito season is the latter part of the summer and they aren't out as much in force in May and early June.