As the larvae of the butterflies and moths, most caterpillars possess highly terrestrial life histories. However, a rare few experience their larval lives underwater in the rocky substrates of streams and rivers or among the aquatic vascular plants of streams, lakes, or ponds. Here, herbaceous aquatic caterpillars often exhibit the same preference for host plants as their terrestrial counterparts, using their chewing mouthparts to graze microflora or feed on certain species of aquatic vascular plants. Like land-dwelling caterpillars, aquatic caterpillars are distinguished by their elongated, somewhat cylindrical bodies, distinctive heads with at most simple eye spots, three pairs of legs on the thorax, and short pairs of prolegs along the bottom of the abdomen.