The size at first sexual maturity is described for females of the Scalloped spiny lobster Panulirus homarus homarus (Palinuridae) sampled from landings at Khadiyapatnam in Kanyakumari district of Tamilnadu, on the southwest coast of India, based on physiological and functional maturity indices. The size at 50% physiological maturity was estimated at 55.0 mm carapace length (CL), based on regression of percent of females with mature, maturing and spent - recovery ovary against carapace length. The smallest female with a mature ovary was 45.5 mm CL compared to the smallest female (46.5 mm CL) with external eggs. Logistic relationships between CL and percentage of females with external eggs (berried) and with ovigerous setae on endopod of pleopods indicated that 50% maturity was attained at 61.0 mm CL (berry method) and 54.0 mm CL (setal method), respectively. Size at maturity based upon appearance of well developed pairs of ‘windows’ on the last pair of sternal plates at the base of fifth pereiopods was estimated at 55.0 mm CL. The analyses show that the external secondary sexual characters may be useful as morphological measures of functional sexual maturity in the spiny lobster Panulirus homarus homarus from Indian waters, as these values are very close to the size at physiological maturity (55.0 mm CL) obtained based on the ovarian maturation. On the basis of this study, a minimum legal size (MLS) of 65.0 mm CL for fishing P. homarus homarus from Indian waters is recommended. 

size at maturity, secondary sexual characters, Panulirus homarus homarus, reproductive biology, spiny lobster.