The Lewis mite (Eotetranychus lewisi) and the two-spotted spider mite (Tetranychus urticae) are the two (2) kinds of spider mites that attack poinsettias (Euphorbia pulcherrima).
Specifically, the Lewis mite is a very small, yellow-colored insect. The two-spotted spider mite is very small too, but a bit bigger than the Lewis mite. It may be green, red or yellow in color. It is called two-spotted because of its two dark spots, one on each side.