The morphological and biological characteristics of Oligochroa cantonella Caradja, a leaf-eating pest of mangroves, were studied by laboratory rearing and field observations. In the laboratory, food consumption increased with age class. Mature larvae consumed the greatest amount of food, especially the 4th and 5th instars, which consumed most of the food supplied for the entire period of larval development. It was concluded that the 4th- and 5th-instar larvae were most harmful, and emphasis should be given to the prevention and treatment of larvae before the 4th-instar stage. populations had a regular distribution, which is very different.In Shatian county, the population density on the inner bar was significantly greater than on the beach. In addition, differences in density were found between populations with different orientations and at different sites of Avicennia marina. The density of O. cantonella was greatest in south-facing populations, and in the middle and upper sites. This may be a tidal effect with the lower site of A. marina being flooded for longer than the upper site, which was only submerged at high tide. By contrast, in Dongwei county, the population density in the crown of A. marina was higher than that at the tide line. The population density in the middle site of A. marina was greater than that in the upper site, and the population density in the upper leaves of A. marina was more than that in the lower leaves. These results may be explained as follows. First, the larvae in the upper site of A. marina were easier prey for wasps and hornets. Second, the larvae of O. cantonella feed in the crown in the evening and morning, moving to the inner and middle-lower site of the crown during the day. In addition, the older larvae were more resistant to flooding, with no mortality observed even after 6 hours' submergence. After 8 hours' submergence larval mortality increased significantly, with 100% mortality being recorded in those larvae submerged for 12 hours. The results indicated that the larvae of O. cantonella were resistant to submergence and adapted to the intertidal environment. Finally, the developmental progress of O. cantonella was found to be influenced by temperature in different regions. Pupae accounted for about 50% of all the worm stages in Shatian county Beihai city, while the pupa of O. cantonella accounted for about 47.1% of all worm states in Yuzhouping county Fangchenggang city. The overall developmental time of O. cantonella in Fangchengang city lagged 5-7 days behind that in Beihai city.