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Head, thorax, and abdomen; three pairs of legs; perhaps one or two developed pairs of wings. Those are the parts you would need to build an insect. But considering that insects can be found in almost every terrestrial and freshwater habitat and some in the marine environment, and can be found eating almost any substance imaginable with nutritional value, your insect could be one of millions of variations on a very successful theme.
Their lifestyles are as varied as their shapes. Some go through an almost magical metamorphosis from caterpillar to butterfly or from wingless, aquatic larva to winged, terrestrial insect. A few hatch from the egg in the form of tiny adults, and shed exoskeleton after exoskeleton as they grow to their full size. Some are carnivorous and control populations of invertebrates harmful to humans, including other insects. Others feed on nectar and pollen, and along the way they provide an essential pollination service to innumerable plant species. Some take part in the decomposition of organic materials, hollowing out rotten logs, churning up leaf litter, or, in the case of the dung beetle, whisking away the waste products left by vertebrates.
But a surprising number of these multi-talented creatures are in danger of extinction, and little information is available on the status of many species. Endangered species lists are biased towards vertebrates; only 4 percent of the threatened species listed by the IUCN are insects, yet insects account for around 72 percent of global biodiversity. Of the insect groups in the U.S. on which we have more information, the percentage of native species in peril (of those listed by NatureServe) is high: 22 percent of dragonflies and damselflies, 58 percent of mayflies, 83 percent of grasshoppers, 84 percent of stoneflies, 26 percent of butterflies and skippers, 35 percent of moths, 58 percent of tiger beetles, and 86 percent of caddisflies. Many of these, such as the Scott’s riffle beetle in Kansas, the unsilvered fritillary in California, or the Sacramento Mountains checkerspot butterfly in New Mexico, are known to be in trouble yet still lack legal safeguards. These high percentages are an indicator that ecosystem health may be failing in some places – protection for these small species, if granted, could act as a safety net for the larger environment.