Earth Almanac: May/June 2001

Damsels and Dragons

Two hundred and fifty million years ago, even before the rise of dinosaurs, they patrolled steaming Carboniferous swamps on veined, translucent wings. As other life-forms vanished from our planet, these ancient predators prospered; today there are few places on earth where you can't find at least one of some of the 5,000 species of Odonata--damselflies and their close relatives, dragonflies. Dragonflies have enormous eyes, while the eyes of damselflies are smaller and set more widely apart. Unlike dragonflies, which keep their wings open while resting, damselflies hold their wings together over their backs. With the first warm days of spring, Odonata nymphs crawl out of still and flowing water, climb whatever's handy, and emerge as adults through splits in their skin. Look for them before they take flight as they rest beside their cast-off exoskeletons, pumping hardening fluid from their bloated bodies into veins in their still-soft wings. Soon they'll be hawking insects and, according to some sources, showing good boys where the pickerel are and sewing the lips of bad boys shut.

Underdogs

Remove the black-tailed prairie dog from its niche in our western plains and--as Americans have discovered over the past century--the whole biota collapses like the sides of a stone arch. This stocky ground squirrel, whose name derives from its bark, is called a keystone species because it provides food and/or habitat for at least 59 vertebrate species--29 birds, 21 mammals, 5 reptiles, and 4 amphibians. The elaborate subterranean design of a prairie-dog town includes bedrooms, latrines, birthing and nursing chambers, pantries, even cemeteries. In May look for youngsters as they stumble up into the sunlight for the first time in their six-week lives. Soon they'll be roughhousing, grooming each other, and greeting neighbors with chirps, hugs, and open-mouthed "kisses." Because prairie dogs eat forbs and grasses, they have been widely poisoned and shot in the mistaken belief that they compete with livestock. Studies, however, show that in aerating and turning over the soil they produce high-quality forage.