The rayon bandana, 3'x2' - indispensable.
The Tilley hat - indispensable.
Sometimes, two bandanas - indispensable.
The headnet - indispensable.
(These bandanas with the headnet were earlier versions, too small to be properly effective.)
One of the biggest aggravations is dealing with bugs. Mosquitoes in the early and mid-summer, horse-flies mid-summer, wasps late summer, and worst of all blackflies late summer and all of autumn right up to permanent cold weather. Luckily in northern Canada these are annoyances but not generally health concerns.
Of all of these, I find mosquitoes to be the easiest to deal with and generally the least bothersome. The greatest annoyance is when one or more get inside your tent. They can also be annoying at meal times in the open, where I will use a bugnet tent for protection and comfort. I generally carry out a seek-and-destroy mission before going to sleep. For this I wouldn't be without a fly swatter. The other bugs generally don't bother in the tent. I don't use insect repellant, effective really only against mosquitoes, but depend on clothing for protection. I have had to occasionally wear a headnet when mosquitoes were especially bad.
Horse-flies are the larger flies including deer flies whose bite is quite painful. I have had them bite through two sweat-soaked shirts. Their buzzing, dive-bombing and fast flight are very annoying. One individual can follow persistently through thick bush for a long distance. They are quite agile and hard to hit. The worst time is when taking a shower. During the peak season, I will delay having a shower until evening to avoid these buggers.
Wasps are generally a problem only when you interfere with their nest, often underground and in trees as well as the easily recognized hanging paper nest. Every year I get stung a few times when portaging or cutting portage trails when I stumble upon a nest. Their bite is even more painful than the horse-fly. I walk away as quickly as possible when even a single wasp attacks, and detour around that area as I go back and forth on the portage. I have had to zig when cutting a portage trail when I wanted to zag, because of a wasp nest. (The only other animal I similarly avoid is a skunk, but for a very different reason.)
Blackflies are BAD. I lump gnats and sandflies (no-see-ums) in this group. I label the level of badness as "bothersome", when a hat, neck bandana and long sleeved shirt are adequate to deal with them. "Very bothersome", when an additional bandana under my hat and draped over and around my head makes them tolerable. "BAD" when the only effective way is to use a headnet, when there will be hundreds of the buggers around my head. They do crawl under clothes and bite in unmentionable places. They are especially bad when you are sweaty, flying into your face, eyes, nose, ears. The saving grace with blackflies is that smoke from a campfire will disperse them, so they don't generally bother at meal times. I can tell when the temperature reaches 10C as the blackflies will become bothersome. Even after a freeze at night, once the temperature comes back up they are mobile again, right up until temperature persistently stays below 10C. I have had to wear a headnet most of the day except for meals, when I will stand in the smoke of a campfire before I remove the headnet.
There are several items of clothing I would not be without. I have three headnets distributed in my gear, one in my "Emergency Belt-Bag" that I carry whenever away from camp. I have two Tilley hats. I have six hemmed rayon bandanas, 3'x2'. Long heavy socks, long pants, long-sleeved shirts.
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And the black flies, the little black flies
Always the black fly, no matter where you go
I'll die with the black fly a-picking my bones
Always the black fly, no matter where you go
I'll die with the black fly a-picking my bones
- From "The Blackfly Song" by Wade Hemsworth