Abstract
There is a difference in the pattern of protein feeding by the 2 sexes of the blowfly Phormia regina Males, whether mated or not, gradually increase their intake from the time of emergence until the 4th to 8th day. Thereafter little protein is taken. The pattern is similar for virgin females, but the volume ingested is greater. Mated females increase their protein intake after each batch of eggs is laid. If females are denied protein at times when the intake would normally be great, they show a decided preference for protein over carbohydrate in a choice situation. Choice is mediated by the contact chemoreceptors; odor is not a factor. The peak in protein ingestion that occurs after emergence is not altered by removal of the ovaries, corpus allatum, or medial neurosecretory cells. Subsequent peaks are abolished by any procedure that prevents egg development. Changes in feeding behavior are correlated with changes in protein levels which in turn are related to hormonal and reproductive cycles. It appears unlikely that hormones are directly concerned with nervous activity leading to protein ingestion.