A Physiological Interpretation of the Marching of Hoppers of the African Migratory Locust (Locusta Migratoria Migratorioides R. & F.)

Abstract

1. Hoppers of the locust Locusta migratoria migratorioides R. & F., which have been reared crowded, exhibit characteristic marching behaviour in the laboratory in foodless cages under standard conditions. 2. The rate of attainment of maximum marching by a given group of hoppers is greatest following a short period of starvation immediately preceding transfer to these conditions. 3. A meal of filter-paper soaked in sugar solution only, exerts no retarding effect on the rate of attainment of full marching, whilst if an adequate concentration of potassium salt is added in addition a definite retardation is observed. 4. In locusts actively feeding on grass the potassium content of the blood is relatively high, and it is suggested that this causes a reduced muscular efficiency which may explain retardation in attainment of full marching. 5. The marching pattern is the result of the activity of particular nerve centres which require a period of activation by a combination of factors before full expression is achieved. Two final factors are essential for the maintenance of the marching state, a low concentration of blood potassium and mutual stimulation by other marching hoppers.