Carlson, C. W. and R. W. Brosemer (Dept. of Chemistry and Graduate Program in Biochemistry, Washington State University, Pullman, Washington 99163) 1973. Amino Acid Compositions of Cytochromes c from Four Hymenopteran Species: Evolutionary Significance. Syst. Zool., 22:77–82.—The amino acid compositions of cytochrome c isolated from honeybees, bumblebees, leaf-cutting bees, and yellow jackets have been determined. The composition of the honeybee protein is less related to that of the other insects than is expected from the accepted phylogeny and constant rates of cytochrome c evolution. This suggests that cytochrome c may have evolved faster in the lineage leading to honeybees than in the lineage leading to other insects.