Polymorphism in Aphididae

Abstract

Thanks especially to the studies by Bonnemaison, Lees, and Johnson, it is possible to understand more clearly the mechanism of polymorphism in the annual cycle of a great many species of Aphididae. In a great number of species, polymorphism phenomena in nature are bound to a certain generation or certain generations. So, in Mindarus Koch, the second generation is alate and sexuparous, and in a great many host-alternating Aphididae the second generation is completely alate and virginoparous. This might be the result of crowding of young larvae, but if such is the case, it is remarkable that second generation apterae viviparse in many such species are not at all known. An autonomous mechanism comparable to the "facteur fondatrice" has not been disproved in such cases. Whether changes in the symbionts play a role in aphid polymorphism or are a result of polymorphism is not known, but according to a personal communication from Dr. P. Buchner they may be absent in some morphs and present in others of the same species.