DISTRIBUTION, STABILITY AND BINDING-SPECIFICITY OF A HEMAGGLUTININ INTHE CORN-EARWORM, HELICOVERPA-ZEA (LEPIDOPTERA, NOCTUIDAE)

A hemagglutinin (HA) was detected during all developmental stages of t he corn earworm Helicoverpa ten. The HA titer was relatively low at th e onset of each developmental stage; it increased very rapidly during each stage and declined considerably just before the onset of the next . The highest HA titer of 4,096 was attained during days 3-5 of fifth- instar larvae. In contrast, the lowest titer of 8 was obtained in adul t insects. Female pupal and adult H. zea had higher HA titers than the ir male cohorts. The hemagglutinin agglutinated red blood cells (RBCs) from a broad range of animals. Its binding specificity was unusual in that the hemagglutination was inhibited by sucrose, N-acetylneuramini c acid, lactose, galactose, maltose, galactosamine and N-acetyl-galact osamine in that order of decreasing effect. The midgut fluid of H. zea larvae contained agglutinins with a specificity that suggests that th ey were exogenously derived from dietary ingredients. Unlike H. zea he magglutinin, which failed to agglutinate flesh mouse erythrocytes, hem agglutinins found in the diet and midgut fluid caused strong agglutina tion of mouse erythrocytes. HA titer fluctuated between and within the various life stages. Unlike many insect lectins, H. zea hemagglutinin is relatively stable after being subjected to repeated cycles of free zing and thawing. Although it is rapidly inactivated at greater than o r equal to 40 degrees C, this lectin is relatively stable at 20 degree s C. Since it is inhibited by 5 mM EDTA, it is probable that the bindi ng action of this lectin is dependent on the presence of divalent cati ons.