![]() In 1996 scientists in Michigan and England reported in the Journal of Heredity (September/October 1996), that during the 1960s, darker-colored moths began to predominate over light, white-and-black-flecked moths in polluted areas. In southern Florida, for example, the sharp decline of swallowtail butterflies alerted biologists to the harm caused by mosquito sprays, as well as to the fact that pesticides had contaminated the water. Because many species are extremely sensitive to changing environmental conditions, the 20,000 known species of moths and butterflies are carefully monitored by scientists and conservationists around the world.īutterflies and moths have alerted scientists to numerous habitat changes. Consequently, healthy butterfly populations tend to occur in areas with healthy ecosystems. Butterflies can thrive only when intact habitats are available for both caterpillars and adults. Butterfly larvae are generally crawling, herbivorous caterpillars, whereas butterfly adults fly and are nectar-eating. Part of the reason butterflies are sensitive to many aspects of the environment is that these species undergo a drastic metamorphosis, or change, from larva to adult as a natural part of their life cycles. The decline of these species serves as a warning to human beings about the condition of the environment. Like amphibians, many butterflies and moths are considered by scientists to be "indicator species" because they are particularly sensitive to environmental degradation. Most of the IUCN-listed species are butterflies, dragonflies, and damselflies, which are among the better examined insect groups. There are also 553 threatened insect species and ten threatened arachnids listed in the 2003 IUCN Red List of Threatened Species from the World Conservation Union. threatened and endangered insects and spiders are shown in Table 9.1. ![]() ![]() species), a group related to insects that includes spiders, ticks, and mites. There are also 12 endangered arachnids (all U.S. Fish and Wildlife Service under the Endangered Species Act. In 2004 there were 39 endangered insects (35 U.S., four foreign) and nine threatened insects (all U.S.) listed with the U.S. Insects have not been nearly as thoroughly studied as the vertebrate groups, and so there are likely to be many endangered insects whose desperate state remains unrealized. Insects are the most diverse group in the animal kingdom, with close to a million named and described species and countless species yet to be discovered. ![]()
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