We took the exact same itinerary, ship and time that you're taking in 2005, that we did in 2004. It was on the Island Princess, end of August, and we took the same cruise tour and cruise and it was our first time to Alaska and we brought mosquito repellant and spray and we did not see even one; not even in Denali. Maybe we were lucky. I don't know. Just go prepared, but we didn't need it when we went last August.
I would love to see Alaska again, but this year, we're taking another cruise to Hawaii in September, so I guess Alaska will have to wait awhile.
PS Of course I packed everything I owned; since everyone said you would be wearing layers of clothing as the temps changed so often, and they were right. Next time I'll know how to pack better for Alaska. One thing I'm glad we didn't forget, was our binocculars and be sure to take a camera.