The differentiation of various ,morphotypes in female population of Mucrobruchium rosenbergii (de Man) identical with their male counterparts from the Vembnad lake has been established on the basis of colour pattern and pattern of spination of second cheliped, structure of dactylus, relative growth and allometric characterization. A sequential pattern of transformation obserbed in female-morphotypes of the Vembanad lake would also support the existence of various rnorphotypes in the population. Orange (OF) and Blue clawed (BF) females are easily distinguished by the presence of orange and blue colours respectively on merus, carpus and propodus while pretransformi,,sgt ages of the former such as weak orange clawed (WOF), strong orange clawed (SOF) and pre transforming orange clawed (T-SOF) female morphotypes are clearly diagnosed by noticing their distinct colour variations. 'Iko types of blue clawed females BF1 and despite having similar colour pattern, can be differentiated by observing the hairs on the dactylus. Information on pattern of spination, relative growth within the population and allometric relationships of various .morphometric characters are also given.

Macrobrachium resenbergii, morphotypes, female population, distribution