The germicidal wavelength is short. Wavelengths shorter than 300nm are generally most effective for killing bacteria. The peak emission of the GE Germicidal lamps is 254 nm. The fluorescent lighting is for plant life while the incandescent lamp is used to provide IR radiation for animals that need it such as lizards. Cautions need to be taken when lighting a terrarium.
Specific requirements depend on species being lighted.
Insects and humans have different visual perceptions. This allows for people to have better control of nocturnal insect nuisances by adjusting the color of lighting. The human visual system is activated by radiant energy in the color range from deep blue to dark red, which we call light. Sources which radiate ultraviolet energy and blue light are most attractive to flying insects, while those with a deficiency of ultraviolet and blue are less attractive. Insects see black light fluorescent, mercury, and metal halide best.