monomorphism
From ZooTerms (Dictionary of Invertebrate Zoology)
population that exhibits a single form. See also polymorphism.
monomorphism (noun; Greek monos, one; morphe, form): 1. A
2. Species that contain only the female sex
See also: dimorphism. 3. (Arthropoda: Insecta) In social insects, having within a species or colony only a single worker subcaste.