An HPLC analysis of hemolymph and accessory gland extracts followed by histological study of neurosecretory cells was undertaken to uncover differences between solitary and gregarious phases of migratory locusts, Locusta migratoria migratoria, reared under either isolated or crowded conditions respectively. Some differences in the chromatographic pattern could be detected. One of the major peaks in the hemolymph of isolated-reared adults was found to be a minor one in the crowd-reared individuals whereas two other peaks seemed to be more pronounced in the gregarious phase. The dominant chromatographic peak in accessory glands extracts of the crowd-reared animals was found to be a minor one in isolated-reared females. In the case of solitary accessory glands, the major peaks seem to be specific to the solitary phase. Histological analysis of the neurosecretory cells shows that solitary female was characterized by the presence of ‘A’ cell cluster in the postero-lateral median region of the pars intercerebralis and it seems that these cells are not active in the gregarious phase. The significance of these gregarious phase specific peptides with respect to neurosecretory cell activity has been discussed.
