Presents the design of the software simulator, VIFS, for insect flight. In particular, it is intended to estimate flight control algorithms and performance for a micromechanical flying insect (MFI), a 10-25 mm (wingtip-to-wingtip) device eventually capable of sustained autonomous flight. The VIFS is an end-to-end tool composed of several modular blocks which model actuator dynamics, wing aerodynamics, body motion, visual and inertial sensors, environment perception, and control algorithms. A 3D virtual environment simulation is also developed as a visualization tool. We present the current state of art of its implementation and preliminary results.