Agrotis infusa
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Agrotis infusa ("Bogong butterfly") |
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| Boisduval , 1832 |
Agrotis infusa , sometimes also called Bogong butterfly , is a butterfly ( moth ) fromthe owl butterfly family (Noctuidae) that occurs in Australia. The species has a complicated life cycle. Most of the moths that hatch in the Australian spring migrate over 1000 kilometers from the original breeding area to the Australian Alps , where they rest in summer and return to the breeding area in the Australian autumn. This part of the population forms only one generation per year. A smaller part remains in the breeding area and forms several generations there.
features
The wingspan of the moth is 30 to 50 millimeters. The front wings are brown to black in the basic color. Ring and kidney defects are relatively large, outlined in light and dark. The hind wings are light gray to light brown.
The egg is initially whitish, hemispherical, and measures 0.5 millimeters in diameter. It later becomes reddish and shortly before the egg caterpillar hatches, it becomes blackish-gray.
The caterpillars are light with a brown head. They turn green when they start to eat. The color can change to brown if several caterpillars live together in a small space. The adult caterpillar becomes up to five centimeters long.
Geographical distribution and habitat
Agrotis infusa is widespread in southeastern Australia . The moths are occasionally driven far by storms. They have already been found in New Zealand, often even in large numbers.
The species inhabits open grass and pastureland.
Way of life
The life cycle of Agrotis infusa is complicated. The smaller part of the total population is multivoltin, with up to three generations per year. The much larger part, however, is univoltin , ie only one generation is formed per year. This part of the moth hatched in the Australian spring (October) makes flights up to 1000 kilometers from the Darling Downs in Queensland and the northwestern plains of Victoria in eastern Australia to the Australian Alps at altitudes above 1400 meters, to be found there in large groups (each estimated with several million animals) to spend the summer months in caves and crevices (" estivation "). The moths hardly consume any nectar during the migration, the sexual organs are still immature. They feed primarily on their fat reserves (up to 60% of the dry weight of the moths), which have already been created in the caterpillar. The subsequent summer rest lasts up to four months. A small proportion of the moths also fly around in the summer spots for short periods. In late summer and early autumn (February to April) the moths migrate back to their breeding grounds, they now visit flowers and suckle nectar. This takes place at night and rest during the day. The sexual organs gradually mature, whereupon when they reach the breeding area they mate and then lay their eggs. Up to 200 eggs are laid at the base of various plant species or in the soil around it. A significantly smaller proportion of the moths hatched in spring remain in the breeding area. These moths begin to suckle nectar and develop sexual organs. They mate and lay eggs again. Depending on the weather, up to three generations are formed each year. The adults of this summer generation are smaller and have white hind wings.
The moths are nocturnal and are disturbed in their navigation by artificial light and attracted by it. In the cities of Sydney and Canberra , for example, this has already created major problems, e.g. B. on and in the parliament building in Canberra. The moths are agile and persevering fliers who fly very purposefully towards their destination. Since they fly at night, when the wind is usually weak, they rarely go off course. However, strong storms can blow them into cities, such as B. 1988, 2000 and 2005, when large numbers of moths drifted to Sydney. In rare cases, they can be shipped across the Tasman Sea to New Zealand.
The caterpillars of both sub-populations hatch three to seven days after oviposition. They feed mainly on annual plants that sprout in autumn with the onset of rain. The growth of the caterpillars is relatively slow due to the low winter temperatures in the breeding areas. They moult five times, which means that there are a total of six caterpillar stages before pupation.
The caterpillars have a wide range of nutrient plants. They are nocturnal and live in the earth, from where they bite off seedlings of various plant species just above the surface and eat them in an underground passage. The host plants include beet ( Beta vulgaris ), cabbage ( Brassica sp.), Pisum , barley ( Hordeum ), wheat ( Triticum ), lupins ( Lupinus ), flax ( Linum usitatissimum ) and lentils ( Lens culinaris ).
From the end of September to October the caterpillars pupate in the ground in a cocoon. The moths hatch after a short pupal rest when the drought sets in in October.
Reproductive strategy
The breeding area of Agrotis infusa is characterized by a shorter, humid and cooler period during the Australian winter and a somewhat longer, dry and very hot period during the Australian summer. Broad-leaved plants and vegetables dominate in winter and grasses in summer. In winter they primarily feed on these plants, the caterpillars of the subpopulation that remain in the breeding area then also switch to grasses. However, the low level of vegetation can only feed a small number of caterpillars during the summer. The migration followed by summer dormancy of most of the population serves to keep the population size high, although the breeding area has unfavorable living conditions for such a large population.
Predators and parasites
The main enemies of the moths on their migrations are bats. The moths have tympanic organs that can receive the sounds emitted by the bats. The moths then begin with evasive maneuvers. In the summer spots, besides bats, mainly (introduced) foxes, mountain bilchbeutler ( Burramys parvus ), New Holland crows ( Corvus coronoides ), currawongs ( Strepera ) and, last but not least, humans hunt the moths. Parasitic nematodes ( Amphimennis bogongae Welch, 1963 and Hexamermis cavicola Welch, 1963), which attack the moths that sit close together, were also found in the over- summer sites . They cause the death of the infected animal. The life cycle of the parasites is synchronized with the arrival, the summer dawn and the migration of the moths.
Use by humans
Bogong butterflies were used as food insects by Aborigines in southeast Australia . The Aborigines went on long hikes in summer to the bogong butterflies' summer spots. The moths were collected, scales and wings were burned in the fire and the moths were consumed. Most of the moths collected were ground into a paste and dried into a cake that was taken to the tribal areas.
swell
Individual evidence
- ↑ a b c George Gordh, Gordon Gordh, and David Headrick: A Dictionary of Entomology. 1000 pp., Wallingford, CABI Publ., 2011 ISBN 978-1-84593-542-9
- ^ Peter Bailey: Pests of Field Crops and Pastures: Identification and Control. 520 pp., Collingwood, CSIRO Publ., 2007 ISBN 978-0-643-06758-5
- ^ KJ Fox: Recent Records of Migrant Lepidoptera in Taranaki. NZ Entomologist, 204 (2): 6-10, 1969 PDF ( Memento from October 15, 2008 in the Internet Archive )
- ^ A b I. FB Common: Moths of Australia. 535 S., 1990 Online at GoogleBooks
- ↑ DP Heenan and GM Murray: Rotational benefits of alternative crops can be affected by their sowing time. Proceedings 6th Australian Society of Agronomy Conference Armidale 1992, p. 496
Web links
- Migration of the Bogong butterflies (abc.net.au)
- Australian wildlife