A developing device including a development part for developing latent images to toner images. Retaining wings are coupled to the anterior section. Further, one electrode which constitutes the capacitance is used in common by the pixels arranged adjacent to each other in the longitudinal direction, and another electrode which constitutes the capacitance is separated between the pixels arranged adjacent to each other in the longitudinal direction. A magnetic field is applied by a varying magnetic field generator to at least a portion of the drop merge area of the substrate, which includes at least the first location on the substrate. A drive assembly is engaged with the first fluid meter and the second fluid meter.