CHAPTER 9
ENDANGERED INSECTS AND SPIDERS

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. 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. In 2004 there were 39 endangered insects (35 U.S., four foreign) and nine threatened insects (all U.S.) listed with the U.S. Fish and Wildlife Service under the Endangered Species Act. There are also 12 endangered arachnids (all U.S. species), a group related to insects that includes spiders, ticks, and mites. Listed U.S. threatened and endangered insects and spiders are shown in Table 9.1.

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. Most of the IUCN-listed species are butterflies, dragonflies, and damselflies, which are among the better examined insect groups.

BUTTERFLIES

Like amphibians, many butterflies and moths are considered by scientists to be "indicator species" because they are particularly sensitive to environmental degradation. The decline of these species serves as a warning to human beings about the condition of the environment. 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. Butterfly larvae are generally crawling, herbivorous caterpillars, whereas butterfly adults fly and are nectar-eating. Butterflies can thrive only when intact habitats are available for both caterpillars and adults. Consequently, healthy butterfly populations tend to occur in areas with healthy ecosystems. 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.

Butterflies and moths have alerted scientists to numerous habitat changes. 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. 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. This was seen in both England and the United States and was probably due to the fact that darker moths were better able to "blend in" to the dingy environment and hide from predators. In both countries, clean air laws were passed and decreases in pollution resulted. Now, in both countries, lighter-colored moths are again predominant. Dr. Douglas Futuyma, a biologist at the State University of New York at Stony Brook, reported that other insect species have shown increases in the proportion of darker-colored individuals in industrialized areas, a phenomenon called "industrial melanism." In those species, as well, the proportion of dark specimens drops as air quality improves.

In many cases, butterflies also help conservationists decide where to locate parks and nature refuges. Generally, the more varieties of butterflies that exist in an area, the more species of other animals and plants will live there too. Unfortunately, many butterfly species are disappearing around the world.

Monarch Butterfly

Historically, monarch butterflies migrated by the millions on a 3,000-mile journey up and down the North American continent. Over time, monarch butterfly populations have also become established in Australia and on the Pacific islands of Samoa and Tahiti. Other monarch populations have appeared in Hawaii and New Zealand.

For many years, naturalists sought to pinpoint the location where monarchs hibernate in January and February in preparation for their mating season and northward migration in March. In 1975, following an arduous search, a serene monarch hibernation area was located in the high altitude forests of the Michoacán Mountains in Mexico. Mexico declared the impoverished region a protected area. The inhabitants of the area turned the site into an ecotourist attraction in order to generate income for the economy. However, ecotourism not only failed to generate sufficient money to support the people of the area, but also caused severe habitat disruption. The onslaught of tourists affected habitats by introducing excessive noise, tobacco smoke, fire, and pollution. Monarch butterflies are now considered endangered by the IUCN. The U.S. Fish and Wildlife Service and the Mexican government have since attempted to nurture a self-sustaining economy in the monarch hibernation area by introducing fish breeding and horticulture.

In January 2002 a massive die-off of monarch butterflies in their wintering grounds in Mexico became major news worldwide. An estimated 250 million butterflies froze to death following a winter storm. As many as 80 percent of monarch colonies may have succumbed. While the storm may have been directly responsible for the deaths, deforestation and logging near the butterfly habitat are believed to have played a significant role. In particular, a fuller and healthier forest canopy would have better protected individuals from extreme weather. Despite the fact that butterfly hibernation areas are in protected reserves, logging continued there until recently. Although the massive die-off was a huge blow to monarch populations, many individuals did survive and it is hoped that the population will bounce back.

MONARCHS AND THE BIOPESTICIDES DEBATE.

Monarch butterflies have also played an unwitting role in the recent debate regarding genetically modified foods. In an effort to reduce the amount of pesticides in the environment, plant geneticists have developed novel hybrid plants that are genetically altered to produce substances called biopesticides. These plants repel pests without additional application of pesticides. In order to create biopesticide-producing plants, scientists insert DNA for pesticidal proteins directly into plant genomes. The introduction of biopesticides generated continuing controversy in the 2000s. Proponents argued that biopesticides were much less toxic than chemical pesticides, and also claimed that biopesticides affected only targeted plant pests without affecting other consumer organisms. Opponents, however, feared that any genetically altered species posed potential and unknown threats.

These fears were substantiated when researchers discovered that one genetic hybrid of corn, called Bt corn, is poisonous to monarch butterflies. Bt corn is genetically modified to include genes from a known pesticidal bacterium, Bacillus thuringiensis. Pesticidal proteins were genetically spliced into the corn genome to create a hybrid that repelled an important pest, the European corn borer. Bt corn was believed to be safe for the environment because it lacked toxins. Researchers reported, for example, that Bt corn had no effect on honeybees, ladybugs, or other organisms that inhabit cornfields. However, a new study reported in 1999 that in laboratory tests involving monarch caterpillars, as many as 44 percent of the caterpillars died after exposure to Bt corn.

Sacramento Mountains Checkerspot Butterfly

The Sacramento Mountains checkerspot butterfly has a highly specialized habitat—it occurs only in meadows at elevations of between 8,000 and 9,000 feet in southern New Mexico. Furthermore, the species is only found where there are native flowering plants, and is absent from meadows where invasive species have taken over. This is because Sacramento Mountains checkerspot caterpillars feed solely on native plant species such as the New Mexico penstemon. The Sacramento Mountains checkerspot is characterized by brown, red, orange, and white checked wings.

The Sacramento Mountains checkerspot is currently proposed for listing as endangered in its entire range. The species was first petitioned for listing by the Center for Biodiversity in 1999. Surveys of population sizes took place between 1997 and 2000 and revealed that the species occurs only in fragmented populations within a 33-square-mile area in New Mexico. The butterfly was officially proposed for listing in 2001; it remained a proposed species as of 2004. It is threatened primarily by loss of habitat due to urban development and destruction of habitat by off-road vehicles and overgrazing. In addition, several invasive plant species are taking over meadows once occupied by native plant species used by Sacramento Mountains checkerspot caterpillars. Finally, over-collection of specimens has harmed populations. A critical habitat of 5,000 acres is being proposed for the species, half of which is on federal property and half of which lies on private property.

Karner Blue Butterfly

The Karner blue butterfly was listed as endangered in 1992. It once occupied habitats in the eastern United States from Minnesota to Maine as well as Ontario, Canada. At present, the species occurs in portions of Minnesota, Wisconsin, Indiana, Michigan, New York, New Hampshire, and Ohio. Most Karner blue butterfly populations are very small and in danger of extinction.

The caterpillars of the Karner blue butterfly rely for food on a species of lupine that is now found primarily on roadsides, military bases, and some forest areas. (See Figure 9.1 for a description of the Karner blue butterfly life cycle.) The primary reason for endangerment of the Karner blue butterfly is habitat loss due to land development for human use and forest maturation. Table 9.2 shows the recovery objectives, recovery criteria, recovery actions needed, total cost of recovery, and expected date of recovery as set out in the recovery plan for the species completed in September 2003. Figure 9.2 shows the recovery units, or populations, of the species, sites for potential recovery units, as well as other sites where the species has historically been found.

As is the case with other endangered species, conservation measures protecting the habitat of the Karner blue butterfly are expected to benefit numerous others rare species as well. Table 9.3 lists other rare species that overlap with the Karner blue butterfly in habitat in the state of Michigan. These include mammals, birds, reptiles, other insects and invertebrates, and a large number of plants. This is one of many examples of how the Endangered Species Act, despite focusing on individual species, contributes to the conservation of many species and to entire ecosystems.

Blackburn's Sphinx Moth

Blackburn's sphinx moth was first listed as an endangered species in February 2000 and is found exclusively in Hawaii. This moth species is threatened by factors such as urban development, conversion of land for agricultural use, invasive plant species, non-native ungulates (hoofed animals), and invasive predators and parasites. Figure 9.3 shows the estimated pre-human contact range of the species in Hawaii, current points of Blackburn sphinx moth occurrence, and current points of occurrence of the native host plant on which the moth depends. Some of the invasive predators and parasites that impact the species, and the islands on which they are found, are listed in Table 9.4. Conservation recommendations in the species recovery plan, which was drawn up by the Fish and Wildlife Service in October 2003, include habitat conservation and restoration, planting of the moth's host plant in new habitats, and a captive breeding and reintroduction program. The total cost for recovery of the species is estimated at $5.5 million.

OTHER ENDANGERED INSECTS

Santa Cruz Mountain Insects

Insects, like numerous other species, suffer from diminished habitat as a result of encroaching development,

industrialization, and changing land use patterns. In California's Santa Cruz Mountains, the tiny Zayante band-winged grasshopper, barely half an inch long, occupies areas containing abundant high-quality silica sand, known as Zayante or Santa Margarita sand. This sand is valuable for making glass and fiberglass products, and several businesses have entered the area in the hope of capitalizing on this. The Zayante band-winged grasshopper joined the ranks of listed endangered species in January 1997. In 2000, as a result of a lawsuit filed by the Center for Biological Diversity, the Fish and Wildlife Service proposed the establishment of critical habitat for the grasshopper.

The Ohlone tiger beetle was listed as endangered in October 2001. The species was discovered in 1987 and is found only in Santa Cruz County, California. The Ohlone tiger beetle is a small species, about half an inch long, with spotted metallic green wings and copper-green legs. Both adults and larvae hunt invertebrate prey. The Ohlone tiger beetle occupies a total of less than twenty acres of remnant native coastal prairie habitat on state land, private land, and property belonging to the University of California at Santa Cruz. The species declined due to habitat loss and habitat fragmentation resulting from urban development, as well as over-collection, pollution from pesticides, and the increasing encroachment of invasive plant species. The petition to list the Ohlone tiger beetle with the Fish and Wildlife Service was originally made by a private citizen in 1997.

In 1998 the Fish and Wildlife Service completed a recovery plan for the Zayante band-winged grasshopper, the Ohlone tiger beetle, as well as other insect and plant species found in the Santa Cruz Mountains. Table 9.5 summarizes a range of conditions that cause harm to a variety of Santa Cruz Mountain threatened and endangered species. Factors leading to endangerment include sand mining, urban development, conversion of land to agricultural uses, recreational use (such as hiking, horseback riding, off-road vehicle use, bicycling, and camping), competition with non-native species, fire suppression, pesticides, logging, and over-collection.

Hine's Emerald Dragonfly

The Hine's emerald dragonfly has been listed as an endangered species since 1995 and is found in federal and state preserves and National Forest lands in Illinois, Wisconsin, Michigan, and Missouri. In earlier times, its range extended through portions of Ohio, Alabama, and Indiana as well. The Hine's emerald dragonfly has a metallic-green body and emerald-green eyes. It is considered a biological indicator species because it is extremely sensitive to water pollution. The decline of this dragonfly species has resulted primarily from loss of suitable wetland habitat, such as wet prairies, marshes, sedge meadows, and fens occurring over dolomite rock. (The lakeside daisy is another species damaged by the decline of these habitats—it is listed as threatened.)

Wetland habitats support dragonflies during their aquatic larval period, which lasts some three to four years. Adult dragonflies occupy open areas and forest edges near wetland habitats, where they feed on invertebrate species such as mosquitoes. Hine's emerald dragonflies also serve as prey for a variety of bird and fish species. The recovery plan for the dragonfly includes measures to protect current habitat as well as reintroduction of the species to portions of its former range. Private companies that own land supporting dragonfly populations have aided conservation efforts by monitoring populations and preserving important habitat areas.

ENDANGERED SPIDERS

Kauai Cave Wolf Spider

The Kauai cave wolf spider is a blind species found only in special caves on the southern part of the island of Kauai in Hawaii. Several cave areas were proposed as critical habitat for this and other endangered cave species, including the Kauai cave amphipod, in 2002. Caves occupied by the Kauai cave wolf spider and Kauai cave amphipod are formed by young lava flows.

Unlike most other spiders, the Kauai cave wolf spider hunts prey directly. Its prey includes the (also highly endangered) Kauai cave amphipod. The Fish and Wildlife Service originally listed both species as endangered in January 2000. Female cave wolf spiders lay some fifteen to thirty eggs per clutch, and carry young on their backs after hatching. Cave species are extremely sensitive to changes in temperature and light. It is feared that official designation of critical habitat by the Fish and Wildlife Service will make the delicate cave systems more prone to human use, resulting in damage from activity including light pollution, garbage (which may attract new species to the caves), and cigarette smoke.

Spruce-fir Moss Spider

The Spruce-fir moss spider is an endangered spider related to the tarantula. It was placed on the Endangered Species List in 1995. Spruce-fir moss spiders live in moss mats found only in the vicinity of Fraser fir trees. Its populations have declined largely due to the introduction in the United States of an invasive European insect species, the balsam-wooly adelgid. The balsam-wooly adelgid infests Fraser fir trees, causing them to die within a time period of two to seven years. With the death of numerous fir trees, other forest trees have also blown over. The resulting increase in light level and temperature causes the moss mats on which spruce-fir moss spiders depend to dry up. The Fish and Wildlife Service designated critical habitat for the species in 2001, including areas in the Great Smoky Mountains National Park and the Pisgah and Cherokee National Forests, as well as a preserve managed by The Nature Conservancy. This designation of critical habitat followed a lawsuit against the Fish and Wildlife Service, which had previously deemed designating critical habitat "not prudent" because it believed the spider would be more vulnerable to collectors.