In a hammock no risk of scorpions those are a bit restricted to sonora desert region. What spiders, would be no problem, not even mosquitoes. I camped out around Mojave, sleeping bag right on the ground, what crawlies I never saw expecting maybe a sun spider or wolf spider. Snakes were my concern for sidewinder tracks and the Mojave rattler home, still none. Moths might be nuisance, even those are scarce.
One recent camping in central Idaho, rain had a couple grass spiders and Opiliones seeking refuge under the rain fly, no problem.