It was shown that the fecundity of aphids may be altered on plants treated with plant growth stimulators and retardants. There was evidence that the reduced fecundity and smaller size of Aphis fabae on broad beans treated with ethylene bisnitrourethane was related to the reduced nutritional value of the plants to the aphids, levels of soluble nitrogen being reduced. The reduced fecundity of A . fabae on broad beans treated with gibberellic acid may be related to the apparent toxicity of the compound when fed directly to the aphid. CCC (chlormequat chloride) seemed toxic to both A . fabae and Brevicoryne brussicae, and the number of embryos per adult A . fabae reared on CCC-treated beans was reduced, although this did not reduce fecundity. Apart from any direct action of CCC on the aphids, there is evidence that the substance may reduce the availability of nutrients from the phloem of treated plants to the insects by reducing translocation, and there is further evidence that amino acid content of the sap may be reduced. IntroductionChanges in aphid performance resulting from applications of growth regulators to host plants were first reported for compounds used as herbicides. Maxwell & Harwoodl showed that the reproduction rate of Acyrthosiphon pisum was increased on broad beans treated with sub-lethal doses of 2,4-D, and Robinson2 found that, of 30 herbicides screened for an effect on this aphid, only maleic hydrazide, amitrole and zytron were active, and these increased mortality of adults and nymphs within the five-day observation period following application. Growth retardants were first shown to affect aphids by van Emden,3s4 who found that the population increase of both Brevicoryne brassicae and Myzus persicae was reduced on Brussels sprouts treated with CCC (chlormequat chloride). Tahori et al.5 showed that there was a similar fall in the rate of population increase of Aphis nerii on oleander leaves standing in solutions of Phosphon, CCC and B995, and B. D. Smith (unpublished) found the same effect on Aphis pomi on apple shoots growing in solutions of CCC and B995. Although there is no published record of growth stimulators affecting aphids, Carlisle et aZ.6 have shown that injections of gibberellin affect the rate of maturation of locusts, and Ellis et aL7 showed that gibberellin-

Aphis fabae reared on broad bean plants treated with the experimental growth stimulator ethylene‐bis‐nitrourethane were extremely pale in colour and this persisted for the life of the individual, even when first instar nymphs were transferred from treated to untreated plants. Pale aphids had less than half the amounts of the pigments protoaphin and aphinin that were present in normal aphids. It is concluded that the aphids probably received a compound which inhibited pigment formation from the treated plants; the chelating properties of the metabolite of the compound in plants are consistent with this conclusion.