부산대학교 도서관

The alfalfa caterpillar, Colias eurytheme Boisduval, is one of the principal pests of alfalfa in California. In the past decade this insect has been of minor importance in southern California but can still be a ravaging menace in central California if insecticides are not used to suppress populations. Alfalfa culture has changed in the past decade in southern California and this may have favorably altered the environment so that this alfalfa pest is now of secondary importance in this area. Data were collected in 1959 and 1960 showing that the egg parasite Trichogramma semifumatum (Perkins) is one of the major biological control agents suppressing populations of C. eurytheme in southern California, but it is not nearly as effective in central California. The distribution of this parasite in California was determined by crosses and reciprocal crosses of field populations collected from various areas in the State. Field and laboratory studies of hosts, sex ratio, number of parasites per egg, and rates of development of T. semifumatum in C. eurytheme eggs are presented. The data clearly show this egg parasite to be one of the key biological control agents maintaining the general equilibrium position of C. eurytheme at a very low level in southern California. Data relating to attacks of Apanteles medicaginis Muesebeck on the larval populations of C. eurytheme in southern California are also presented.