Aphids are parasitic on the foliage, stems, and roots of plants. Many are host specific, and various species are well-known agricultural pests. Slow-moving and soft-bodied, they are vulnerable to a host of predators, but make up for high attrition by their rapid reproductive rate and ability to produce winged adults to disperse to fresh feeding sites. Most aphids have paired abdominal tubes (siphunculi) for expelling honeydew--the sugary byproduct of their sappy diet--which is irresistible to many insects. Ants especially are known for tending aphids, offering protection in return for a sweet treat.