SummaryProteins homologous to vertebrate immunoglobulins have been reported absent from the blood of several insect species. An investigation was made of the possible presence, in larval honeybee blood, of proteins migrating in the globulin region in immunoelectrophoresis. Blood of larvae 5 days old, either whole or fractionated with ethanol or ammonium sulphate, was analysed by Polyacrylamide gel electrophoresis and immunoelec-trophoresis using rabbit blood antiserum. One protein was found that appeared to be comparable to mammalian blood globulins; precipitation arcs associated with this protein migrated in the globulin region during immunoelectrophoresis of whole larval blood or of the globulin-like antigenic solution precipitated by ammonium sulphate. Other globulin-like or albumin-like proteins separated on acrylamide gel do not necessarily have the nature of mammalian globulins or albumins, since they migrated in both the albumin and globulin regions during immunoelectrophoresis.