The Encarsia formosa is a parasite of the greenhouse whitefly, Trialeurodes vaporariorum, a pest of many plants in indoor and outdoor gardens. Greenhouse whiteflies are typically found on poinsettias, tomatoes, peppers, cucumbers and other plants that grow fairly close to the ground. Each container includes 1,000 eggs. Gardeners simply mail in the postcards or register online to have their insect orders shipped to their doors at no extra cost.