Tuesday, 08 January 2013 00:00

Asclepia fruiticosa

Written by  Sue Oxborrow
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African Monarch Larva African Monarch Larva

 

The Milkweed is a herbaceous shrub-like plant that grows to an approximate height of between 1,5 to 2 metres. It has a distinctive “giss” to it (giss = its general impression, shape and size) and is unmistakable to identify in a field. The blade-shaped leaves with their tapering ends grow out from short stalks while the creamy yellow flowers hang downwards in clusters of up to 10 flowers. In the summer, the fruit of the Melkbos reminds one of inflated balls with a tapered end, covered in softish spiky hairs.

The African Monarch butterfly (Danaus chrysippus) larvae feed on the Milkweed which is a toxic plant as it contains cardiac glycosides. Their larvae ingest the toxins and are therefore not palatable to bird predators. There are, however, other species of butterflies that mimic the colours and patterns of the African Monarch, thus lessening their chances of being preyed upon by birds. The African Monarch larvae are preyed upon by the Braconid wasps that lay their eggs inside the larvae. Once they hatch, the wasp larvae eat the African Monarch larvae (which have by this time metamorphosed into caterpillars) and in turn use the caterpillar skin to spin a cocoon on and then begin their own metamorphism to an adult wasp.

Who doesn't enjoy the beautiful flight of the butterflies as they visit our gardens? We watch with interest as they land on flowers seeking the nectar on offer. People don't generally plant Asclepia fruiticosa (Milkweed) in their gardens, as it is commonly classified as an unwanted weed! So, the next time you find a Milkweed on your property, remember the important role this plant plays as host to the African Monarch butterfly's larvae and to its continued survival in our area. Remember too, not to eradicate too many caterpillars that may be found on your plants, as they are busy metamorphosing into those beautiful butterflies we so enjoy visiting our gardens.

 

Asclepias fruiticosa

Asclepia fruiticosa, its fruit and flowers

 

African Monarch larvae

African Monarch in the caterpillar stage of its metamorphic life cycle.


References:  Vincent Carruthers. 2000. The Magaliesberg; Braam van Wyk and Sasa Malan. 1998. Field Guide to the Wild Flowers of the Highveld; Jill Reid. 2000. Butterfly Gardening in South Africa; and Roy Trendler. 2005. Attracting Wildlife to your Garden in Southern Africa.

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