Yeah, bugs also make SUL tougher. In Mallorca I didn't have any problem with bugs, come to think of it, which means I can ditch the head net in my gear list (I included it out of habit it seems). Bugs are pretty thick here in Sweden, and if can be downright torture if you end up camping in the wrong place without any anti-bug gear, like say next to a bog in the middle of summer. Not only mosquitoes, but midges too, plus horseflies, and on top of that lots of ticks. So long as you take a few precautions and have good planning it's really not a big deal, but your baseweight will take a hit. Bug oil/spray, head net, pants/long sleeves, and shelters with netting are all very good to have here.
I have traveled though Scotland several times and the midges are just as bad as Sweden, especially up in the highlands. I remember standing on a beautiful cliff in Tongue, way up north Scotland highlands. As soon as the sun went down, even with a sea breeze, the midges were thick.
I saw on a documentary just the other day that according to a study done in Canada, an exposed arm in the woods during the summertime can get up to 250 bug bites in an hour, if I remember correctly. It was the one where Ray Mears goes on a boat trip through Canadian wilderness.
The worse story I have of being eaten up by bugs was last summer while camping up near the Norwegian boarder next to a lake. I wanted to camp on a cliff above the lake, but my friends wanted to camp right next to the lake so we could swim easier. I wanted to swim too, so I didn't put up a fight, but I did count on getting lots of bugs. It blew my expectations away. We had bug spray and a fire going at sunset, and it made no difference. The midges came a cartoon-like cloud over our campsite and didn't give a hoot about spray or fire, and we were eaten alive. I even had a head net, but the nasty little buggers would crawl under it! They would even crawl up my pant and windbreaker sleeves to feast on me. We all ended up calling it a very early night and hiding out in our tents (thankfully I opted to go with my Big Agnes FCUL 1, which has great bug netting). Even opening and closing the door of the tent to get water or go to the bathroom would cause a mini-cloud of midges to swarm into the tent.
I vote midges worse than any other biting bug, because it's never just one or two or ten or even a hundred of them... it's millions and millions in clouds. And they are so small it makes it so hard to stop them from getting into everything and everywhere. I had a ton of bites on my thighs, and I wore pants, in the above example!