If your good at wood working this site
http://edis.ifas.ufl.edu/uw290 has plans for a bat house, let nature take care of the insects for you and bats are very effective at controlling bugs, but yes seals in good condition also help, or you could swap out whatever type of light your running and go with a low pressure sodium light, they do attract the lowest amount of insects, but nothing is perfect in outside lighting bugs still seem to find a way in so you just clean them out every so often..