Cotton-cowpea intercropping system can be one of the most important practices for the increase of natural enemies and the reduction of pest numbers. This chapter was written aiming at the analysis of intercropping biomass, as well as arthropods relationship. Initially, a wide review was performed to give support to the development model in order to explain the biomass and the relationship between pest and natural enemies in sole or intercropping systems of cotton and cowpea. It was observed that several previously developed models as well as the model here proposed suggest that the increase in plant biomass and natural enemies depend on the pest number and cropping systems arrangement.