Abstract
While engaged In work on truck crop and deciduous fruit insects in Southern California the authors have had an opportunity to make many observations on predaceous insects among which the Syrphidae are of first rank, particularly in their relation to the aphid fauna. Although many observations have been made in all parts of Southern California, most of the data contained herein are from studies made in Los Angeles, Orange and Imperial Counties. While an attempt has been made to study all the species of aphid-feeding Syrphidae, it has been impossible to thoroughly cover all the territory, particularly the mountain and desert regions. The data have necessarily been largely confined to observations made on the Syrphidae which attack aphids on crops commercially grown.
