Summary
The postmarsupial development of Atlantoscia floridana (van Name, 1940) was studied, with emphasis on the sexual differentiation and maturity. Samples were obtained in the Reserva Biológica do Lami, Porto Alegre, RS, Brazil, during 2000 and 2002. Collected animals were reared in the laboratory under temperatures of about 20±1°C and observed daily. Animals preserved in 70% ethanol were used to analyze sexual maturity. Growth was monitored as each animal moulted for evidence of sexual differentiation. The development of the male genitalia and the female genital pore was described across the different juvenile stages. Female sexual maturity was estimated to occur at a minimum size of 1.04 mm cephalothorax width. Male sexual maturity was estimated from the morphometric relationship between cephalothorax width and length of the genital papilla and indicated the puberal moult to occur at a minimum size of 0.77 mm cephalothorax width. Identification of the size at which sexual maturity occurs allows recognizing the postmarsupial juvenile stages of both males and females: JUI to JU III for males and JU I to JU VI for females. Males reach sexual maturity in approximately 1.5 months after leaving the marsupium, and females in about 3 months.