Another alternative to rearing gray hairstreaks in closed containers is to use the twin cup method.  The advantage of this method is that the stalks of the host are in water and it stays fresher longer where you don't have to change it out once or twice a day.  To set it up, simply place host cuttings through the hole of one cup to rest in another cup of water.  Last, place a screen lid on top.  This video demonstrates how this is accomplished.