Because gray hairstreak caterpillars can be cannibalistic, it becomes practical to rear them in separate containers such as storage containers, squat tubs, or restaurant supply condiment containers (i.e, solo cups.) Using closed containers is advantageous over using terrariums or buckets in that it lowers the setup time; but also is more time consuming because you generally need to change out caterpillar frass and host plant every day.  Make sure you puncture holes in these closed container to allow caterpillar frass to dry.