Earth Almanac: May/June 2002

Part of the twilight magic of streams and ponds are caddis flies, mothlike insects that emerge from daylight retreats to hover and dip or skate over the surface, sometimes vanishing into silver craters made by rising trout. Throughout North America, 1,400 known species representing 26 families come in a variety of dimensions and colors--from the size of gnats to the size of dragonflies, and in most every shade of brown, yellow, and green. Spring is the best time for watching both adults and larvae. Get to the water when there's still plenty of light, then study the bottom. Eventually, you'll see little "sticks" and "pebbles" moving over logs and stones. Pick them up and you'll find they are aquatic "caterpillars" that have encased themselves in sand or bits of wood, shell, or other detritus. They feed on algae or carrion. A few forms don't build protective cases but hunt prey or catch it in tunnels or webs they weave with silk.

Barren-Land Bounder

Under the more arid regions of our Southwest, in dens lined with plant material, kangaroo rats are giving birth, usually to two to four young. The animals you see now, almost always at night, are likely to be males. There are 22 species, many of them threatened or endangered because so much of their habitat has been developed or tilled. Like their namesakes, kangaroo rats propel themselves with well-developed hind legs, balancing with long tails. In some species the tails are longer than the bodies, and by swinging them the animals can change directions in midleap. As they exhale, kangaroo rats are able to recover water vapor through their nasal passages, and they can metabolize the water they need from seeds. So powerful are their kidneys that they require only a quarter of the water used by humans to excrete the same amount of urea.