This work deals with the bionomy of the population of Homalaspis plana (Milne Edwards, 1834) sampled in Coronel, Chile. Homalaspis plana share his biotope with: Paraxanthus barbiger (Poeppig, 1836) and Gaudichaudia gaudichaudi (Milne Edwards, 1834). A marked sexual dimorphism is apparent, the males are larger and heavier than the females; moreover, the volumes of the chelae of the first are also larger. The percentaje of the female population was significantly larger than the males population. The spawning extends from June to December. Each class of the ovigerous females, gives a different contribution, the maxima is done by the 5,74 cm class with 29,21%. The minimum size of ovigerous females is 49,3 mm L.C
