Workers in biological control are often confronted with a complex consisting of the host insect in the country where control is being undertaken and in other parts of the world, the series of natural enemies occurring in the country of origin, and the several pest insects that may serve as alternate hosts of certain of these natural enemies. All of these must be detd. correctly if satisfactory progress is to be made in biol. control. Taxonomic papers and insect collections often yield information of direct value in the soln. of biol. control problems. Much of the progress that has been made in the projects for the control of the red and yellow scales (Aonidiella spp.) and the black scale (Saissetia oleae) in California, the sugarcane leaf-hopper (Perkinsiella saccha-racida) in Hawaii, and of several species of mealybugs (Pseudococcus spp.), in various parts of the world, has been due to the taxonomic studies that were conducted concurrently with the field work. Much of the work on Trichogramma in the control of a series of crop pests is of questionable value because of uncertainty regarding the identity of the races or strains that were released.