have a very narrow acceptable temperature range. Their metabolisms have adapted to cold temperatures., and they are the only known worm to spend their entire life in temperatures near 0 C (32 °F), where they are most active and their ability to produce adenosine triphosphate (ATP) is at its peak. They freeze at around −6.8 °C (19.8 °F), and their bodies decompose after continuous exposure to temperatures above 5 °C (41 °F). This decomposition process, known as autolysis, occurs when the cells produce digestive enzymes and self-destruct. The body, figuratively, melts. Even if other places are equally cold, ice worms never venture onto any other terrain. They eat the abundant snow algae and pollen carried by the wind. Ice worms are most active in late spring. In the summer, they follow a diurnal cycle—at the first light in the morning, they sink into the glacier. A few hours before sunset, they poke out from the snow. In this respect they resemble some other oligochaetes that avoid strong radiation but are attracted to dim light. Little is known about the ice worm during the winter as the inaccessibility of glaciers prevents further study. Since in the winter the surface temperature on a glacier can reach −40 °C (−40 °F), the worms most likely remain below the surface. They may burrow as deep as several feet into the glacier in search of an area with a favorable temperature. The snowfall provides insulation, and the temperatures below remains a stable 0 C (32 °F). Ice worms can still find plenty of algae in the firn layer, the layer of packed snow in transition to ice. In glacial ponds or small streams, ice worms can be found in broad daylight. The freezing water provides the worms with a comfortable temperature, countering any heating of their dark bodies from the sun. In fast-flowing glacial streams, ice worms cling to the ice surface. Researchers have observed the worms gyrating their heads in the stream, possibly catching algae and pollen carried by the water. In still ponds, ice worms gather in bundles. Researchers speculate this is reproductive behavior. Ice worms do not graze in groups on the surface, so the contact in still ponds provides the rare opportunity for breeding. Ice worms move on the surface of ice at about 3 m/h (meters per hour) and move through snow by squeezing between the grains. Lateral movement is