In this month’s episode of Field Notes , Susan Knight explains how a tiny relative of our mosquito holds the key to all that chocolate you plan to eat tomorrow on Valentine’s Day. Valentine’s Day is coming up, and with it, a celebration of chocolate. Almost everyone loves chocolate, but you may not realize that the hero of the chocolate story is a tiny biting midge, a relative of our friends the mosquito and black fly. Chocolate comes from the cacao tree, a small evergreen tree native to