Henry Shires got there a long time ago. His whole business is designing tarps with netting sewn onto them. He gives away the pattern for his original homemade tarptent on his site.http://www.tarptent.com/projects/tarpdesign.html
Also, on this very website:http://www.backpacking.net/makegear/jones-tent/index.html
Also, on Quest Outfitters, one of many good sources of fabric and netting:
Seattle Fabrics has a bilgy pattern:http://www.seattlefabrics.com/bilgy.html
some premade options from backcountrygear.com at left in sidebar:http://www.backcountrygear.com/tent/Bug_Netting.cfm
some light examples of net tents designed to go with the SMD tarptents but could be used with a tarp:http://sixmoondesigns.com/nettents.html
Lots to study and possibly replicate. Quest, OWFINC or Seattle Fabrics all have noseeum netting to keep out the buggies smaller than skeeters.