An intrinsic factor influencing alate production by two strains of the pea aphid, Acyrthosiphon pisum

Abstract

Alate virginoparae of a pink and a green strain of pea aphid and both first-born and last-born representatives of several successive generations of their apterous descendants were exposed to a standard crowding treatment in order to determine whether or not they could be induced to give birth to alate offspring. Alatae of the pink strain which were crowded shortly after the onset of parturition subsequently produced very few alate progeny. Their first-born apterous daughters, however, when similarly tested were highly responsive to this stimulus as were all apterae of the next two generations. Crowded alatae of the green strain produced no alate offspring. The ability to respond to such tactile stimulation returned after a period of time to some of their descendants, was lost in females born later, but was found still later to return again. The existence of some sort of timing mechanism is suggested by the present results since representatives of various generations of this strain regained simulataneously and later lost the ability to respond to a crowding stimulus.