These are whiteflies. They come into the home on newly purchased plants or on plants moved inside from outdoors. Both the adult and larval stages of these insects suck plant juices. Their feeding turns a plant's leaves mottled and yellowed.
Whiteflies secrete a clear, sticky substance called honeydew.
Plants usually tolerate this pest, making control necessary only for cosmetic reasons. Yellow sticky traps will control small whitefly populations. You can buy these traps at garden centers or make your own by covering a yellow boardwith tanglefoot or motor oil. Resmethrin is the most effective insecticide. Make three applications five days apart.