Levuana moth
| Levuana moth | |
|---|---|
 | |
 | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Lepidoptera |
| Family: | Zygaenidae |
| Genus: | Levuana |
| Species: | L. iridescens |
| Binomial name | |
| Levuana iridescens Bethune-Baker, 1906 | |
The Levuana moth (Levuana iridescens) [1] was a species of moth in the Zygaenidae family. It is monotypic within the genus Levuana. The Levuana moth is a purple moth that became a serious pest for coconut plants in 1877, in Viti Levu, Fiji. On the island, outbreaks of the Levuana moth were frequent, and as a result coconut palms were devastated due to feeding moth larvae on the underside of leaves. As a consequence, copra (dried coconut meat from which coconut oil is extracted) production was severely affected and coconut cultivation be came unprofitable on Viti Levu. Indigenous Fijian culture, which relied on the coconut for food, water, fiber, medicinal products, fuel, and building materials, was threatened as a result of this coconut pest. In 1916, following a forty-year isolation on Viti Levu, the Levuana moth began expanding its range to close offshore islands, a variety of cultural and chemical control strategies over approximately a 16-yr period failed to bring this pest under effective control,[2] until around 1925 when a historic biological control program devised by John Douglas Tothill permanently reduced high population densities to almost non-detectable levels.
While no recorded documentation of Levuana sightings has been made since the 1920s, some believe that it existed in refuges up until the mid-1950s.[3] However, this island group is most likely not the home range of this moth and it likely originated in island groups to the west of Fiji. This is supported by the fact that although only found in Fiji, no native parasite existed there.[4]
The young larval stage of the Levuana was an insatiable eater of coconut tree foliage. Beginning in the 1870s, hordes of the moth would decimate coconut plantations and adjacent native tree populations. Initially only located on the Fiji island of Viti Levu, Levuana eventually spread to neighboring islands, including the main coconut producing island of Vanau Levu. Without a formidable predator, Levuana population continued to rise until the species was so numerous it was considered by many a pest.[5] Many attempts were made to eradicate the species as such a pest, all of which were unsuccessful until the 1925 biological control program.[2]
This species has a wingspan of 16 mm and is a day-flying insect.[2] The head and thorax are steely blue, the abdomen and legs are ochreous.[6]
Canadian entomologist John Douglas Tothill spearheaded the campaign to lessen Levuana's numbers. Hoping for a major drop in moth populations, Tothill proposed the introduction of a parasite Levuana was susceptible to. However, because the Levuana moth was a species only found on Fiji, a direct and effective parasite was not readily available. Tothill then introduced the parasite of the Artona moth, a related species. The Bessa remota, a Malaysian fly species, proved immensely successful in lowering Levuana moth populations.[7]
Controversy
In 1925, J.D. Tothill and colleagues sought out to cut down the Levuana moth population. Tothill had managed to drastically curb the Levuana moth’s numbers by introducing the Malayan tachinid fly (Bessa remota) to the Levuana iridescens environment. This form of biological control was employed to ensure the survival of the copra crop which grew from the coconut palm that was threatened by the Levuana. Copra, next to sugar, is the most significant industry in Fiji, and since 1877, the foliage of the palms had been eaten by the moth's larva to the point of ruins.[8] This push to oust the coconut moth of Fiji was met with harsh reprimand and criticism due to the controversy surrounding such a deliberate and targeted extinction of a species. The Levuana moth was aesthetically beautiful and had many biological attributes. However, scientific and biological data has shown evidence that the moth was most likely not completely eradicated and had spread its population to other neighboring islands.[9]
There is controversy over the usage of hyperparasitoids to cause preemptive extinction of the Levuana moth. The controversy concerns deciding which is more important: the cultural sustenance which comes from the crops of the Pacific Islanders, or the protection of a species as unique as the Levuana iridescens.[9]
There are also many arguments about whether or not biological control is worth implementing in the first place. Although there has not been much evidence of parasitoids posing any harm to humans, animals, or plants, questions arise as to whether or not previous implementations of this practice actually have, in fact, resulted in harm, whether it is even affordable to test the effectiveness or detrimental side-effects of biological control, if lab testing is precise enough to measure these effects, if more harm will arise from simply doing nothing, or if biological control is significant enough in the issue of exotic species preservation to research into.[10] It is believed that the use of hyperparasitoids caused harm to other species on Fiji as well. It is highly likely that it could have caused the other species to go extinct.[9]
To this day it is unknown whether or not the Levuana moth is truly extinct or not. Although the biological control program dramatically decrease the population of the moth, It is still possible that it is still existing today, but in very small numbers. The Levuana moth preferentially attacks the tallest coconut palms in highly localized areas. When the tallest palms are defoliated, the moth moves on to shorter ones. Based on the fact that severe outbreaks no longer appear, it is theorized that this insect solely inhabits its preferred feeding sites: the tallest trees, in small quantity, leading to visual searches on small immature coconut palms to be unsuccessful.[2] It is believed that if they still exist, they are inhabiting the neighboring islands of Fiji.[9]
Sources
- World Conservation Monitoring Centre 1996. Levuana irridescens
2006 IUCN Red List of Threatened Species (downloaded 31 July 2007).
References
- ↑ Global Names Index, globalnames.org; accessed
- 1 2 3 4 Hoddle, Mark. "Historical Review of Control Programs for Levuana iridescent in Fiji and Examination of Possible Extinction of this Moth", Pacific Science (October 2006).
- ↑ New, T.R. "Biological Control and Invertebrate Conservation", Invertebrate Conservation and Agricultural Ecosystems, Cambridge: Cambridge UP (2005), p. 174.
- ↑ Howard, L. O, "The Cocoanut Moth in Fiji" Science vol. 72, issue 1867 (1930).
- ↑ Insect on Palms. New York: CAB International (2001), pg. 56.
- ↑ New African Lepidoptera, Bethune-Baker (1906).
- ↑ Waldbauer, Gilbert. "Chapter 2." What Good Are Bugs? Insects in the Web of Life. N.p.: First Harvard UP, 2004, pp. 206-08.
- ↑ Howard, L. O, "The Cocoanut Moth in Fiji", Science, vol. 72, issue 1867 (1930).
- 1 2 3 4 Kurmis, Armand M. “Did biological control cause extinction of the coconut moth, Levuana iridescens, in Fiji? Biological Invasions 5 (2003): pp. 133–41.
- ↑ Van Driesche, Roy G. “Should arthropod parasitoids and predators be subject to host range testing when used as biological control agents?”, Agriculture and Human Values 14 (1997): pp. 211–26.