Control of gamic and parthenogenetic reproduction in winged aphids by temperature and light

Abstract

That temperature has a strong influence on the inauguration of gamic reproduction in aphids has long been believed. The ground for this belief has been chiefly the fact that gamic forms, in those species which have them at all, appear usually in the fall. Very little evidence from controlled experiments has ever been obtained. Within tile last few years there has been a suggestion that the duration of light also influences gamic reproduction, but the experimental evidence of this is likewise slight. The previous work on both temperature and light as agents affecting the mode of reproduction has been reviewed recently (SHULT, 1929a), and is therefore not discussed here. The existence of intermediate aphids, repeatedly mentioned in the literature, indicates that differentiation between parthenogenetic and gamic reproduction not be a single sharply defined event. It may be either a gTadual process or a series of events occurring at different times. An understanding Of the precise nature of intermediates might reasonably be sought if the environmental agents producing them were exactly known. With this object in view, the effects of temperature and light have been intensively studied in one aphid, Macrosiphum solanifolii. Since all of the known intermediates relating to the mode of reproduction appear to be those between gamic and parthenogenetic females, and since gamic females are regularly produced by winged mothers, this study has been limited to t h e effect of temperature and light on reproduction in winged females.