Abstract: Tea mosquito bug [Helopeltis theivora Waterhouse (Hemiptera: Miridae)], one of the major pests of tea, have been studied in a randomly collected population sample from Badlabeta tea estate, upper Assam. DNA isolated from insects, separated on the basis of pronatum colour, show polymorphism using Randomly Amplified Polymorphic DNA primers-Polymerase Chain Reaction (RAPD-PCR) with seven primers. Phenograms on the basis of banding patterns were constructed using Numerical Taxonomy System (NTSYS-pc) version 2.02e. A similarity matrix based on the simple matching coefficient was generated by the SIMQUAL program and cluster analysis performed with the Unweighted Pair Group Method with Average (UPGMA) in the Sequential Agglomerative Hierarchal and Nonoverlapping (SAHN) program. The constructed phenogram shows that one colour variant is distinctly different from the rest three. The study indicates that the population consists of discontinuous phenotypes among individuals within a freely interbreeding population which has many of its hosts in the vicinity. Genetic variation among the phenotypes within a population focuses on some evolutionary mechanisms which may resist the effect of pesticide.