The distribution of CREB mRNA was investigated by in situ hybridization in the brain of three castes of Polyrhachis vicina.Extensive expression of CREB mRNA was observed in the brain of all three castes.The prominent positive reaction was observed in the Keyron cells of mushroom body,the optic lobe and the olfactory lobe.Relatively higher expression was found in the olfactory lobe and mushroom body of workers' brain as well as in the optic lobe of males' brain.These results suggest that CREB may play a critical role in obtaining and integrating the visual and olfactory information in the nervous system,and may be relevant with social community behaviors.