the best way to get large firm bugs is to feed them their food of choice.....
but do you really want bugs in your grow room? You don't want bugs in your pants.........therefore you should not want them in your grow.
Poking fun aside. Ducting and a filter are a must in my book. Your plants need co2. If you are not drawing in fresh air to replenish their supply, you will need to provide co2 via a tank, shrooms, or other means. You will also want a filter even if you do not pull in fresh air and vent out just to help contain or eliminate the smell. Even though you are in a legal state, and may love the smell of your plants, your loved ones or neighbors may not.