Effects of population density on alienicolae of Aphis fabae Scop.

Abstract

SUMMARYA wide range of morphological differences, from apterae to alatae, and of differences in the behaviour of alatae were produced by isolating alatiform nymphs of Aphis fabae on successive days after their birth. Alatiform. nymphs isolated soon after birth developed into the extreme apterous form, whereas when kept in a crowd until shortly before their final ecdysis a large proportion became alatae that flew before depositing young (migrants). Alatiform nymphs isolated on successive days after birth developed either into alatae that flew after depositing nymphs (flyers) or did not fly (non‐flyers). Aphids thus show a continuous polymorphism, comparable to that of locusts, and possibly related to concentrations of juvenile hormone present in the aphid during larval development.

THE EFFECT OF LIGHT ON THE RELATIONSHIP BETWEEN APHIS FABAE SCOP. AND ITS HOST PLANT, VICIA FABA L.

“…Groups of five matched plants were selected for the treatments as described above. Plants were infested by placing clip-cages containing 10 alate A. fabae (from a culture maintained on V.faba stipules; see Shaw, 1970) on the underside of each leaf of the first pair. Empty cages were placed on control plants.…”

“…The cotyledons had little infiuence on the response of the plants to tbe aphids, which in turn hardly affected tbe rate of depletion of the cotyledons. This is a little surprising, since large aphid colonies can be cultured on single stipules of decapitated V.faba plants, for which the cotyledons provide virtually the sole food source (Shaw, 1970). The main factor affecting the rate of use of the cotyledon reserves was, in fact, ligbt.…”

Aphid Polymorphism and “Darwin's Demon”

“…These developed into adults with reduced and deformed wings and a soft, partially unsclerotized thorax. However, when synthetic JH mimics Aphis fabae is of this type (Shaw, 1970).…”

A model of temporal distribution of Aphis gossypii (Glover) (Hem., Aphididae) on cotton

“…A colony is composed of first to third instars, apterous fourth instars, alatiform fourth instars, apterous adults and alate adults. The alates appear in the colonies in response to certain factors such as the crowding effect and the modification of the physiology of the host plants ( Shaw , 1970; Bonnemaison , 1951; Dixon and Glen , 1971). This stinging insect causes considerable damage to the cotton plant, while stinging for feeding.…”