on land seek out sites underground where temperatures consistently remain above freezing, although wood frogs and chorus frogs simply burrow in the leaf litter and depend on chemicals to make them freeze-tolerant; during hibernation, more than 40 percent of their body fluids can consist of ice. Other frogs and turtles hibernate at the bottom of ponds and lakes. Insects Insects are critical components of boreal food webs and play important ecological roles as pollinators and decomposers, yet as a group, they are among the most poorly understood organisms in the boreal region. Except for relatively few species, mainly those considered "pests" because of the economic losses they cause by damaging or killing trees, or highly conspicuous groups such as butterflies, little more than the names and general habitat preferences is known. It is estimated that 32 000 insect species inhabit Canada's boreal forest, although about one third of these species have yet to be described. Among the known species, several are particularly well adapted to their habitat. For example, black fire beetles have infrared sensing organs on their bodies that allow them to track the heat of forest fires as they search for freshly burned trees on which to lay their eggs. Other species, like the white-spotted sawyer beetle, use their long antennae to sense chemicals in smoke and charcoal to achieve the same goal. Like many other insect species, in addition to starting the decomposition of fire-killed trees, these two beetle species are an important part of the diet