Dear Rabbi Simon
I bought moth stickers, or whatever they are called, not exactly moth balls, but the effect is that they kill moths and their larvae. Having already bought them, I am now wondering if that is halakhically permissible since you are killing an insect? If so, must one remove these devices on Shabbat?
The reason I bought them is that so many if my skirts and sweaters have holes in them and I thought that moths might be part of the problem. (Or am I passing up an obvious excuse to update my wardrobe?) But a living thing is a living thing…
TY for your interesting and sensitive Q. Killing insects is permitted (not on Shabbat or Yom Tov) if they are a menace to you or your property. In general, while wanton destruction or taking of life in any form should be avoided, where human wellbeing is advanced thereby, it is allowed. BTW, I am not sure if a moth larva has the status of a fully formed creature in halachic terms. Note also that the moth deterrent you describe probably keeps moths away as well as killing those already in its vicinity. The first property is certainly allowed. No need to remove them on Shabbos as their work is subtle and automatic.
So live and let live, but not at the cost of your wardrobe becoming a moth colony.
Rabbi Rashi Simon