For many years now, biologists are studying the numbers of harmful species, and regulatory factors in the use of mathematical methods. Now researchers in the majority of the population dynamics of the pest determinant of the two factors - dependent (regulator) and independent (modified), their density in accordance with the denomination. The Independent factors uniformly act on the pests, regardless of their number. This is mainly climatic factors. In contrast, a number of factors, depending on the density (within Amount competition, predators, parasites, diseases) enhance the scope of its activities, with an increase in the number of population. The process is described by differential equations containing nonlinear connections. In particular, we relied on the equations of Volterra-Lotka and Kolmogorov. As is known, it is impossible to find an analytical solution of such an equation and to conduct a qualitative analysis using phase portraits.