ABSTRACT
Two scorpion species of medical importance occur in the state of Säo Paulo the native brown scorpion Tityus bahiensis (Perty) and the highly toxic yellow scorpion Tityus serrulatus Lutz and Mello, which was brought into the state. The study of accident data of patients admitted to the Vital Brazil Hospital of the Butantan Institute from 1982 to 1993 revealed a gradual increase in stings by T. serrulatus in contrast to those by T. bahiensis which a variation from 5.2 per cent to 29.7 per cent. Also, an inventory of the scorpions sent to the Laboratory of Venomous Arthropods of the Butantan Institute over the same period showed an expressive growth in the number of T. serrulatus specimens in contrast to that of T. bahiensis. These data suggest a significative proliferation of T. serrulatus in the state of Säo Paulo over the past 12 years, and a probable interspecific competition between T. serrulatus and the endemic T. bahiensis. The analysis of scorpion accidents reported to the state of Säo Paulo Health Department (Secretaria de Estado da Saúde de Säo Paulo) corroborated the higher severity of T.serrulatus envenoming. The results pointed to the possibility of an increase in severe envenoming and deaths by scorpion stings in the state of Säo Paulo. Aiming to contribute to scorpion prevention and control programs, the present geographical distribution of both dangerous species was mapped, pointing to the areas of higher risk of scorpionism in the state.