Yes, another Star Trek episode. This one was striking for its explicit Malthusianism (!). The tribbles increase “arithmetically,” to use Malthus’s term — Spock notes that one tribble (bisexually) breeds on average ten tribbles a mere twelve hours later. And what is it that the tribbles end up doing? Trying to eat away a fixed supply of grain. Yes, grain. Might the tribbles exercise Malthusian moral restraint? No, they are born pregnant. Again, as Malthus suggests, a plague (poisoning) intervenes.