a wide variety of pygmies could work for that, easiest probably being the pygmaea, pulchella, scorpiodes, etc.
Yes, if the appropriate conditions are given to them during the summer- i.e. dry soil, high heat, etc.- then they will go into dormancy by themselves.
I have heard you can prevent this by always keeping the soil wet and not letting it dry out, but I haven't had any personal experience with this.
good luck w/ your bog.