Two temps. (24P and 14[degree]), 2 light conditions (continuous and intermittent), and 3 antecedent temps. (24[degree], 14[degree], and alternating) from which parents were drawn for the experiments, were combined with 2 types of individual (winged and wingless Macrosiphum solanijolii) in 24 different groups of experiments. Without any change of conditions there was a decline in the proportion of winged offspring with increasing age of the parents. At either high or low temp. and in continuous light, this age effect was not much modified, even if the conditions prevailing represented a change. Of the external conditions, light was most important in this strain of aphids, continuous light inducing many more winged offspring than did intermittent light. Temp. was next most important, high temp. inducing more winged offspring than low. Wingless parents produced more winged offspring than did winged parents if the parents came from low temp., but the reverse was usually (though not markedly) true if the parents came from high or fluctuating temps. High temp. with intermittent light caused at first a decline and later in the same families a rise in wing-production in the offspring, regardless of the other conditions. Some of the above responses directly reverse those given by the same line before 1929.