I found myself in a bit of a jamb last week because I forgot to bring a bug net with me for a three day mid Missouri Bush Whack. I had some spare material in my supply box and was able to whip this net together a few hours before setting off on our hike. I assembled an envelope measuring 90 inches by 36 inches. In the bottom I sewed in a cord channel that holds some mason line with a tiny cord-lock. There is a small gap in the top corners through which my whoopie slings are routed. The net snugs up against the gathered hammock ends to form a tight seal. The draw cord could easily by replaced with shock cord, but at the time I had to work with available materials. The net ends up as a soft seal type - the body of the hammock fills out to form the closure. I had no issues with bugs what so ever. Worked like a dream. If no bugs are around it is a simple matter of sliding the net off of the slings, and Bob's your uncle.
Also shown in these pics is my new DIY 4 Season Man Cave Tarp which was made specifically for this trip.