672. Spontaneous Generation

Shabbos 11:2

One is as liable for killing insects and worms that reproduce through sexual reproduction, or fleas (which were believed to spontaneously generate), as for killing an animal. Conversely, one was not considered liable for killing other insects and worms that were believed to spontaneously generate. [Editor’s note: There is a difference of opinion as to the status of this halacha now that science has disproven the concept of spontaneous generation.]

Shabbos 11:3

One who checks his clothes for lice on Shabbos may rub them off and throw them away. It was considered permissible to kill lice on Shabbos because they were believed to spontaneously generate. [Editor’s note: the practical application of this halacha in our post-spontaneous generation worldview is beyond the scope of these emails. Please consult your rabbi.]