I use an integrated net.
I treat both the hammock body and net with permethrin so I don't deal with bugs biting through anything. Besides the reasons already stated by others, I use it all year round. I never have a time when I "don't need it". Even in winter it traps a significant amount of heat. In the fall/spring this is even more noticeable as when you unzip it, you can feel the rush of cooler air. This allows me to get by with a warmer rated quilt in colder temps. I also like to have my tarp flipped to one side so I can see the stars but ready to stake out at a moments notice when the weather changes. The net stops leaves, pinecones, sap, squirrel doodoo from landing on my face or quilt.