aphid

Any of several species of sapsucking, soft-bodied insects (order Homoptera) that are about the size of a pinhead, with tubelike projections on the abdomen. Serious plant pests, they stunt plant growth, produce plant galls, transmit plant viral diseases, and deform leaves, buds, and flowers. Ants may take care of aphids, protecting them from weather and natural enemies and transferring them from wilted to healthy plants. The ants in turn obtain honeydew, a sweet product excreted by aphids, which the ants retrieve by “milking” the aphids (stroking their abdomens).