1. The developing time of the mealybug from catalpa exceeded that of the mealybug from apple. 2. In no experiment did cross-breeding of the mealybug from apple and from catalpa take place. 3. Each mealybug was able to live successfully on both hosts. 4. The parasites, Clausenua purpurea Ishii, from the mealybugs from catalpa parasitized the mealybugs from apply failed to parasitize mealybugs from catalpa. 5. Some female mealybugs may overwinter in the adult form if fully protected from the weather and if the temperature does not drop below 45 °F. 6. Under optimum conditions, several mealybugs lived exceptionally long lives, passing a maximum of 145 days. 7. A color differentiation of the females of the two mealybugs was noticeable. / Master of Science