It is more or less generally accepted that most of the so-called secondary products are important for the fitness of plants. They may either serve to attract pollinating or seed-dispersing animals or, more relevantly, to inhibit the growth of microorganisms and of other plants or to repel the feeding of herbivorous animals [1]. However, nearly all plants, irrespective to the chemical or mechanical defence they have evolved, possess a few pathogens or predators. Compared to the number of potential enemies, the number of the specialized pest species is exceedingly small. The specialization of these species usually consists in their capacity to overcome the plant's defence system [2]. Lupins and other Leguminosae produce quinolizidine alkaloids which are assumed to be important as chemical defence compounds in plant-plant, plant-microorganism, and plant-herbivore interrelationships [3]. In this communication we report on an aphid species, (Macrosiphon albifrons), which has specialized on alkaloid-rich lupins. We show that this aphid accumulates lupin alkaloids and can use them for its own defence.