No wounding, killing or trapping any living creatures on Shabbos! Here we must draw a careful distinction between the biblical prohibition, for which one becomes liable to bring a sin offering if the transgression is unwitting, and the rabbinic prohibition, for which there is no punishment, but we obey in order to distance ourselves from sin. Both constitute halacha, the law. Eight creeeping things may not be trapped or wounded by Biblical prohibition. Lice were thought to be a special category, but one of the sages was ahead of his time in understanding that they procreate like all other animals. Rambam teaches, when you find a contradiction between Scripture and science, you have misunderstood one or the other or both.