Butterfly and moth migration
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Migration by butterflies and moths is widely known and recorded. A wide number of species exhibit this tendency of which the most famous is the Monarch butterfly.
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[edit] Relevance of magnetism during butterfly migration
Recent studies have shown that tropical butterflies use the earth's magnetic field like a compass during migration. The studies were carried out by Dr Robert Srygley and his associate Javier Hernández in Panama. They studied the butterfly Aphrissa statira which migrates annually from Panama's Caribbean coast to the Pacific during the months of May to July.[1]
Tropical butterflies are known to use the angle of the sun against the horizon as a guide during migration. However this does not work when the sun is overhead and no directional clues are available for the butterflies. Dr Srygley theorised that the butterflies might be using the Earth's magnetic field like a compass. Supported by a grant from the National Geographic society, he proceeded to test the theory.[1]
Specimens of Aphrissa statira butterflies were caught while migrating South over Panama's Lake Gatún. Each day at noon when no directional clues are available, the team released groups of butterflies into a covered cage surrounded by a weak electromagnetic field. When the electromagnetic field was reversed, the butterflies flew in a direction opposite that of their known migratory path. If the butterflies were exposed to a strong electromagnetic field before release they scattered more as compared to butterflies that were not so exposed to strong fields. In both tests, control groups of butterflies, that were not exposed to any manmade electromagnetic field, followed their correct migratory path.[1]
[edit] Boogong moth
Bogong moth is a native insect of Australia that is known to migrate to cooler climates.
[edit] Migration of butterflies through Mukurthi National Park
Butterfly migration involves the flight of large number of butterflies for long distances in a single direction. Sixty of the approximately 250 spp of butterflies known to migrate occur in India. These largely belong to the Nymphalidae and Pieridae butterflies and to a lesser extent, the Lycaenidae and Hesperiidae.
Mukurthi National Park is located in the Nilgiris district of Tamilnadu state of India. In Nov 2002, the following butterflies have been observed to migrate in a mixed swarm of thousands of butterflies towards the Silent Valley National Park in Kerala :-
- Family Papilionidae.
- Graphium agamemnon Tailed Jay.
- Graphium sarpedon Common Bluebottle.
- Family Nymphalidae.
- Hypolimnas misippus Danaid Eggfly.
- Hypolimnas bolina Great Eggfly.
- Euploea core Common Crow.
- Danaus chrysippus Plain Tiger.
- Tirumala limniace Blue Tiger.
- Family Pieridae.
- Delias eucharis Common Jezebel.
- Three unidentified spp.
The migratory swarm tended to follow the valley and were most populous during the day when bright sunshine was available. The swarm was seen to be predated upon by insectivorous birds such as Pied Bushchat Saxicola caprata, Nilgiri Pipit Anthus nilghiriensis, Tickell's Warbler Phylloscopus affinis, Greenish Leaf-Warbler Phylloscopus trochiloides and the Oriental White-eye Zosterops palpebrosa.[2]
[edit] Notes
- ^ a b c Kaufmann, Carol - 'Butterfly Magnetism' (Expeditions), pg 34, National Geographic magazine, May 2006, Washington DC.
- ^ Senthilmurugan B. Mukurthi National Park:A migratory route for butterflies. (Aug 2005) J. Bombay. Nat. Hist. Soc. 102 (2): pp 241-242.
[edit] References
- Kaufmann, Carol - 'Butterfly Magnetism' (Expeditions), pg 34, National Geographic magazine, May 2006, Washington DC.
- Senthilmurugan B. Mukurthi National Park:A migratory route for butterflies. (Aug 2005) J. Bombay. Nat. Hist. Soc. 102 (2): pp 241-242.
