The interaction of the Bernstein-Green-Kruskal (BGK) wave (N=1) with the Langmuir wave was studied in numerical experiments. It was shown that the interaction leads to the stochastic instability (the formation of the stochastic layers) or to the large scale stochasticity. The evolution of the large scale stochasticity is accompanied by the secondary nonlinear effects, which lead to the increase of the amplitude of the BGK and Langmuir waves and to the increase of the Chirikov parameter. The final stage of the large scale stochasticity evolution is the formation of a new quasistationary structure on the phase plane, which includes the region of stochastic motion. It was shown that the BGK wave itself is unstable due to the interaction with the Langmuir waves excited by the electric field of the electron density distribution in the BGK wave, which leads to the stochastic instability or the large scale stochasticity. 4 refs., 22 figs., 9 tabs.