An invasion of the llanera locust Rhammatocerus schistocercoides occurred in 1994 in the Oriental Plains of Colombia, causing damages in agricultural and cattle production of the region. Previous studies of this species demonstrated that three biotypes: green, brown and red are present on individuals of a same population. The phase polymorphism theory express that Acrididae may change of a solitarious to a gregarious phase or viceversa, expressing changes in morphometric characteristics in colorations and in behaviour. These insects are considerated are true locusts. Although R. schistocercoides have a gregarious behaviour is not recognised as a locust, therefore the objective of the work was to verify the presence of phase polymorphism in this specie. Green nymphs were placed in cages individually and grouply and the changes of the coloration was observed in order to describe the morfological and coloration characteristics in females and males adults belonging to biotypes red, brown (gregarious) and green (solitarious).