Endangered Species in the Pacific Islands
Blackburn’s Sphinx Moth / Manduca blackburni
||Blackburn’s sphinx moth is Hawai‘i’s largest native insect, with a wing span of up to 5 inches (12 centimeters).
Like other sphinx moths, it has long, narrow forewings and a thick, spindle shaped body tapered at both ends. It is grayish brown in color with black bands across the top margins of the hindwings and five orange spots along each side of the abdomen.
|Blackburn's sphinx moth - Photo credit Ellen VanGelder
The large caterpillars occur in two color morphs, gray or bright green with scattered white speckles throughout the back and a horizontal white stripe on the side margin of each segment.
|Grey Caterpillar - Photo credit Ellen VanGelder
||Green Caterpillar - Photo credit Ellen VanGelder
Habitat & Behavior:
Historical records of this species are mostly from coastal, lowland, and dryland forests in areas receiving less than 50 inches (120 centimeters) of rainfall, though they have been collected from sea level to 5,000 feet (1525 meters). It was most common historically on Maui. Larvae of Blackburn’s sphinx moth feed on native ‘aiea trees (consuming leaves, stems, flowers, and buds) and other plants in the Solanacea family. However, some of the host plants recorded for the species are not native to the Hawaiian Islands, and include tree tobacco, and tomato plants.
Development from egg to adult can take as little as 56 days, but pupae may aestivate (dormancy during a period when conditions are hot and dry) in the soil for as long as several months. Adult moths can be found year round but seem to be most active during two periods, January to April and September to November. Adult moths are known to be strong fliers.
Past & Present:
Once found on six of the Hawaiian islands, the moth now exists only on Maui, Kaho‘olawe, and the island of Hawai‘i. They were believed extinct until 1984 when a small population was rediscovered in a lowland dry forest on the south coast of east Maui (Kanaio area).
Additional small isolated populations are now known from other parts of Maui including Kanaha Pond and Spreckelsville. Populations were recently discovered on Kaho‘olawe (the first record of this species on this island) in 1997 and in 1998 in North Kona on the island of Hawai‘i.
Threats to Blackburn’s sphinx moth include continued loss of habitat, introduced ants and parasitic wasps that prey on the eggs and caterpillars, and the loss of its native host plant, ‘aiea, which is a dryland forest tree.
The native host plant is found in endangered ecosystems, dry and mesic forests, and has been adversely affected by feral animals, alien plant invasions, and habitat conversions associated with development. Ants are not a natural component of Hawai‘i’s arthropod fauna and they are particularly destructive due to their high densities, aggressiveness, and broad range of diet. A high percentage of the eggs of the sphinx moth are destroyed by alien parasitoid wasps and ants. In addition, the moth may also be susceptible to overcollection by individuals for their personal collections or for trade. Because the remaining populations are small and restricted, the potential for extinction from a chance event, such a fire or a hurricane, is greatly increased.
This native Hawaiian moth was the first Hawaiian insect to be added to the endangered species list by the U.S. Fish and Wildlife Service. The Service is currently funding research examining the life history, captive rearing, and conservation biology of the sphinx moth. Additionally, the Service is currently a partner in a dry forest restoration project on State lands in the same area that the North Kona population of the moth occurs.
The Kanaha Pond Sanctuary dune restoration project is currently being modified to include planting of the native host plant since sphinx moth larvae were recently observed on plants in the sand dune area in the Sanctuary. The military uses part of the general area where the east Maui population occurs for training and has adopted measures to prevent fires, alien seed dispersal, and vegetation damage as a result of training. While no conservation efforts specifically for the moth are currently underway on Kaho‘olawe, the State, the Kaho‘olawe Island Reserve Commission, and the U.S. Navy are aware of the presence of this species and have sponsored surveys to identify the distribution of the moth on the accessible parts of the island.