Moth, Blackburn's Sphinx

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Moth, Blackburn's sphinx

Manduca blackburni

phylum: Arthropoda

class: Insecta

order: Lepidoptera

family: Sphingidae

status: Endangered, ESA

range: USA (Hawaii)

Description and biology

The Blackburn's sphinx moth, called pulelehua in Hawaiian (meaning "flying lehua flower that lasts a short time"), is the largest insect in Hawaii. Its wingspan is 5 inches (12 centimeters). It is grayish brown and has black bands across the top of its rear wings and orange spots along its abdomen. The forewings are long and narrow and the body is like a rounded stick with tapered ends.

Because the Blackburn's sphinx moth is very rare, little is known about its habits. However, it is a member of the sphinx moth family and shares many traits with better- known members of this family. These moths are often called "hummingbird" or "hawk" moths because they are so bird-like in looks and behavior. Like hummingbirds, they are strong fliers notable for the rapid movements of their wings. They feed like hummingbirds by hovering over a flower to sip the nectar.

Sphinx moths usually mate quickly after reaching adulthood. The female sphinx moth may lay as many as 1,000 eggs, usually on the surface of an 'aiea, a native Hawaiian plant that is its preferred host plant. A few days later, the eggs hatch. The male and female die after reproducing. In its larval (caterpillar) stage, the Blackburn's sphinx moth is a 3.5- to 4-inch (9- to 10-centimeter) caterpillar, almost the size of a hot dog. The caterpillars can be either bright green or gray with white spots or lines. They are usually called "hornworms" because they have a red or black horn on their abdomen. The caterpillars feed on plants from the nightshade family, particularly the 'aiea plant, from which they eat the leaves, stems, and flowers. However, this plant is becoming rare—two of the four 'aiea species are listed as endangered. Blackburn's sphinx moths also eat plants that have been introduced to Hawaii, such as a variety of tobacco plants, as well as eggplant and tomato. After the larval stage, the insect goes through the pupal (cocoon) stage, for which it goes underground. In this stage, it transforms, to eventually rise up to the surface as an adult moth.

Habitat and current distribution

The Blackburn's sphinx moth occurs from sea level to 2,500 feet (763 meters) in dry coastal forests. No one knows the number of adult or larval Blackburn's sphinx moths, but it is believed that there are currently four populations on the Hawaiian Islands of Maui, Kaho'olawe, and Hawaii. The main population is in Maui at Kanaio, a natural reserve. This population resides in an area that is both publicly and privately owned. Part of the public area is a natural reserve, while another part of the public area is training ground for the Hawaiian National Guard.

History and conservation measures

At one time the Blackburn's sphinx moth occurred throughout the Hawaiian Islands on Kauai, Oahu, Molokai, Maui, and Hawaii. It was most common in Maui. After the 1940s, very few of the species were observed. In the 1970s, after an extensive search for the species failed to turn up any specimens, it was thought to be extinct. Then, in 1984, a population of Blackburn's sphinx moth was discovered at Kanaio. Since then, three other populations have been discovered.

The primary threat to the Blackburn's sphinx moth is the destruction of its habitat by deer and by feral animals (animals that were once domesticated but have become wild), particularly goats. The animals eat the native plants and trample their roots and seedlings. The native 'aiea plant, which is important to the moth's survival, is being destroyed rapidly. Because these moths have become so rare, they have become valuable in the international market for insect specimens. Humans hunt them for trade. Military maneuvers by the National Guard within the moth's core habitat pose a threat, as do accidental fires in the arid region. Ants and parasitic wasps prey on the eggs and caterpillars.

The Blackburn's sphinx moth was the first Hawaiian insect to be placed on the U.S. Fish and Wildlife Service's endangered species list. In the early 2000s, research into captive breeding and conservation of the sphinx moth is ongoing. Work is being done to restore the dry forests that are home to the remaining populations. The 'aiea is being planted in the Kanaio habitat. The military groups that use the training grounds within the habitat are being educated about the moth and its preservation.