Electrophoresis and immunodiffusion of proteins from the hemolymph of the large milkweed bug, Oncopeltus fasciatus (Dallas) (Hemiptera, lygaeidae)

1. 1. Starch gel electrophoresis of hemolymph from fifth instar nymph and adult milkweed bugs may give four anodic and eight cathodic protein fractions. The anodic band closest to the origin is the predominant fraction in hemolymph from insects of both stadia and either sex. The two cathodic bands closest to the origin stained for protein with an intensity slightly less than that of the predominant anodic band. 2. 2. All the protein fractions of hemolymph from fifth instar nymphs and adults of either sex contained antigens which reacted with antiserum to fifth instar nymph hemolymph. Protein fractions taken from corresponding portions of the starch gel block gave reactions of identity. One antigen was common to all fractions. At least four different antigens were detected. 3. 3. The presence of the major nymphal proteins in the adult hemolymph is discussed with regard to the feeding behavior and life cycle of the insect. 4. 4. Some of the hemolymph proteins bound Evans Blue, but dye bound to hemolymph protein did not have the mobility observed when it was bound to human serum albumin.