If we've been hiking long enough, there will be times when we have unwanted hiking partners, not the two legged variety but the biting insect kind. The basic biting insects that we have to contend with in Ontario are mosquitoes and black flies. Both are active by May and gradually become less of a problem as the summer goes on.
Mosquitoes breed in stagnate water and are the most active at dawn and dusk.
Black flies remain active all day. Mosquitoes and black flies are attracted to our body warmth and release of carbon dioxide, both pretty hard to turn off while we are hiking. There are a few strategies we can try such as wearing protective, lighter coloured clothing, and avoiding perfumed soaps and shampoos. Unfortunately, these have only limited success, so we should look at insect repellents. The most effective repellent is Deet.