Intimate Relations

S1 E4: Ever since they came onto land, the tiny creatures of the undergrowth have been forming alliances and partnerships with each other and with plants. Many of these relationships are staggeringly complex. While some clearly benefit both partners, others most certainly do not. Meet the bot fly which uses smaller house flies as unwitting couriers to carry its eggs to cows, where they hatch and bore into the unsuspecting animal's flesh.