What are you doing for insect control while trekking?

There's a lot to be said for Keith's method of drinking rum. If you self-medicate enough, you may not feel a thing. 

Depending on the species, insects detect humans and animals through CO2 and other chemical signatures in exhaled breath, body temperatures, sweat, etc. Their ability to detect can be masked, jammed, or diverted away from an individual by being tricked into going after a hotter, sweatier heat source they will go after instead of someone less tempting. Anything that helps reduce their ability to find us by washing up at the end of the day, staying cool, etc, will all help before applying natural compounds.

Military training frequently teaches the idea of not walking on trails, and not bunching up. That thinking can also be applied to being outdoors. Animals moving across game trails are a form of transportation for ticks, chiggers, and other parasites they encounter along trails. I suspect parasites have higher population densities along trails where they can find "food" and locate others of their species, than there is in dense brush where animals don't often live in/around/near or cross over. If that might be true, staying off game trails might mean heavier going through brush and rougher natural terrain, but possibly less troublesome in regards to the numbers of blood suckers....on the trails.

Not bunching up in military terms means the chances of being wounded or killed because people are close together translates into people not being close enough together that insects detect several "targets" that are relatively close together than a single one with a much smaller detection profile.

Personally, I'm more concerned about ticks and the possibility of Lyme's Disease. Whenever I'm in long grass, in the woods, etc, I always do a personal inspection to locate and remove any ticks I find. Deer populations in and around suburban housing areas in the eastern US means ticks hitching rides on deer are increasingly being found in backyards, and I routinely check pets these days. No one wants Lyme Disease, or for that matter the risk of a single pregnant tick laying eggs inside their house and a possible infestation....