Violent Hippie
WKR
I've used a waterproof bivy as my only shelter in the Sierra a good bit primarily from 6500 -13000 ft and only experienced some mosquito's near water or marshy areas especially if the prior winter was wet. The wet areas can be REAL bad with mosquito's for months but no other creepy crawlies really . Some rattlesnakes in the lower elevations of the Sierra foothills and coastal ranges of So CA. In a fully enclosed bivy sleeping in heavy mosquito areas is no problem for me.In my experiences in AZ and UT I have seen a good amount of gnarly spiders and scorpions and some rattlesnakes . Ticks are all over the lower elevation (under 6k) in CA and the deer are infested . AZ and UT I've never seen a tick although I know others who have.Western rattlesnakes in my experience are not aggressive at all and I have no problem sleeping in the open in their territory . Nothing compared to the copperheads and water moccasins I've encountered in the SE US.