Sunday, 24 February 2008

The Monarch Butterfly

Probably the most commonly seen butterfly around Napier is the White.

Possibly the most common, although because it is very small (25mm wingspan) and lives very close to the ground it is rarely seen, is the Common Blue.

However the most noticeable is the Monarch or, in Maori, Kahuku. The Monarch arrived in New Zealand at least 120 years ago having crossed the Pacific from North America. It is this country's largest resident butterfly and is very common on warm sunny days particularly near its caterpillar's food - the swan plant (Gomphocarpus physocarpus). It spends two weeks as a caterpillar, two as a chrysalis then lives for about 2 months as a butterfly.

So this photo is one that I took when near Exeter with CJ, Helen and Ian last September. It is a male: note the black scent pouches near the bottom of the black veins nearest the body.

I would probably have written this posting anyway because the Monarch is so beautiful but I was even more fascinated by its migration story.

The Monarch is the only butterfly in the world known regularly to undertake [note the joined infinitive] a two-way migration. Indeed one female holds the record for the longest known insect migration, having flown 3432 kilometres from Canada to Mexico. At average speeds of up to 130 km each day this would have taken almost a month flying at altitudes of up to 1000 metres. Each year, at the end of summer, at least 100 million Monarchs [not an endangered species yet then!] make a similar southward journey to the mountain ranges of Mexico where they hibernate in the pine forests. At the end of winter they mate and start on their long journey back North. The most incredible thing about this northward journey is that it takes up to 5 generations 'leap-frogging' each other until the great, great, great grandchildren find their Canadian summer home again! How do they know where to go? No one knows.

In spite of its incredible journeys overseas, however, New Zealand Monarchs do not migrate long distances.

I have only once seen a Monarch butterfly land here although they fly around constantly very close - particularly on the Croquet lawn where they 'buzz' the balls. On the occasion that I did see one land the batteries ran out on my camera just before I tried to take the photo. By the time I'd put the new batteries in it had gone. Ah well.

Gomphocarpus physocarpus - Swan Plant

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