An incandescent lamp is provided with a phosphor coating on its lamp envelope. The phosphor coating alters the spectral distribution of radiation emitted by the lamp and acts as a diffuser. In one embodiment, the phosphor coating absorbs radiation at wavelengths below 500 nanometers and emits radiation at wavelengths above 500 nanometers to provide an improved bugfoiler lamp. In another embodiment, the phosphor coating absorbs radiation in the ultraviolet, violet and blue wavelength range and emits radiation at longer wavelengths that more effectively stimulate the human eye.