Ecology of Toxoptera Graminum, Especially as to Factors Affecting Importance in the Northern United States.*

The unexpected and severe outbreak of Toxoptera graminum Rondani, a grain aphid often called the “green bug,” in Minnesota in 1926, has led to an investigation of factors governing such outbreaks. Such a study seems desirable because of the light it may throw on its capacity for injury, especially in the north. It is also of interest because of the need for more information on the life economy of the aphid group in general.