When pea aphids, Acyrthosiphon pisum, were raised on an artificial diet which mimics the amino acid composition of the total tissue of aphids, their intracellular symbionts in the bacteriocyte gradually decreased in number as the host generation proceeded, accompanied with a decrease of the host's fecundity. It is possible that host sacrificed its symbionts to supplement the artificial diet that is nutritionally deficient. This inevitably incurs aposymbiosis, which will, in turn, lead to the host's sterility, as observed repeatedly.