Q&A from the Bais HaVaad Halacha Hotline

Flee, Fly!

September 7, 2023

Q My outdoor garbage bin is inundated with flies and bees. When I deposit a garbage bag and close the lid, I’m trapping insects inside. May I do so on Shabbos?

A Tzad (trapping a live creature) is one of the 39 melachos of Shabbos. The Rama (O.C. 316:3) rules that it is therefore forbidden to close a box that has flies inside. Even though the user doesn’t intend to trap the flies—he just wants the box closed—this is a case of psik reisha (“cut off the head,” i.e., the unintended outcome is inevitable), because the flies will surely be trapped.

Mide’Oreisa, the melacha of tzad only applies to a species that is commonly trapped (bemino nitzod), e.g., livestock animals, which are useful for work, meat, and hides (Shulchan Aruch O.C. ibid. 1). Most insects are of no use to people and so are not b’mino nitzod. Because this case is only forbidden mideRabanan, certain leniencies apply:

• If the garbage bin is very large, and the flies inside have enough free space to fly around to avert a trapping attempt, it is permitted to close the lid (Mishnah Brurah ibid. 15). While usually tzad applies (mideRabanan) even in a large enclosure, here it is permitted because the quarry is not bemino nitzod.
• If you are unsure whether there are flies in the bin, you may close it. Because trapping flies is asur only mideRabanan, the rule of safeik deRabanan lekula applies (Mishnah Brurah ibid. 16).
• If the bin has a hole, even a fly-sized one, you may close the lid. Because the flies could potentially find the hole and escape, their trapping is not inevitable, so there is no psik reisha (Mishnah Brurah ibid. 14). If there is no hole, you may close it if you leave the lid slightly open to allow egress.

Some say that bees are bemino nitzod because they produce honey, so the above leniencies don’t apply. But most poskim equate bees with other insects (Mishnah Brurah ibid. 13).