Didn't get any responses in another forum, so posting here. I am thinking about going up to southeastern Maine (not too far from the coast) in mid-June. What can I expect in terms of black flies, mossies, and other pesky biting insects? Will I miss the worst of it? Mike

That depends on where.
Generally, by then they should be tapering off. Around water? You will see plenty, though. They vary by a week or two, depending on the spring. With all the wet from the snow, IFF we also have a wet spring, yeah, they will be bad.
Info:
http://www.mainenature.org/blackfly/blackflyinfo.html

I frequent the ADK's where there is a much more confined season. And more water conducive to breeding.

Movement is one thing that works. Keep hiking. DEET helps with immediate exposed skin. They are still attracted to you, but they don't like to land and bite. Warm evenings can be real anoying...fully enclosed tents are almost required. Smoke from a fire, cigar and ilk keeps them out of your face. Breezes and winds are good to disburse them, but you might still get a few bites. Towards the middle and end of the season, mosquitoes will mix in. Permethrin will usually prevent these from getting thrugh your clothing.

Enjoy! Fish love them. Small size 18 black flys are excelent fishing.