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The butterfly

29 July 2014

 

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Butterflies and moths are members of the Order Lepidoptera of the Class Insecta. They are scaly-winged insects and have membranous wings that are covered with overlapping, dust-like, microscopic scales. The name of the Order Lepidoptera is derived from the ancient Greek words lepidos for a scale and pteron for a wing.

There are some 20 000 species of butterfly in the world, of which 666 are known to occur in South Africa in 19 subfamilies. Carolus Linnaeus, a Swedish-born naturalist, was the first to describe the butterflies scientifically in the 18 th century. The species are differentiated partly on the basis of the patterns which the scales form on the wing.

Butterflies are ancient insects and could have flown around the dinosaurs as the oldest known fossil butterflies date back to 65 million years ago. Fossil butterflies that are preserved perfectly occur in amber deposits in the Dominican Republic that are 40 to 50 million years old. The name butterfly is of Middle-English origin and refers to the beating of the wings. The butterfly is a symbol in many ancient cultures, including that of the Maya, and usually represents beauty and rebirth. However, in some regions a butterfly is regarded as an omen of evil and some battles have even been suspended because of the sighting of a butterfly. The ancient Greek name means soul or mind. The tomb at Giza of Queen Hetep-heres I of Egypt contained several beautiful bracelets with a butterfly image set in turquoise, a semi-precious stone that was highly prized at that time. Butterflies also appear in marsh scenes that were painted on the walls of several tombs.

Butterflies are excellent indicators of environmental health because they are sensitive to environmental changes, especially the presence of toxins. They go through four phrases of growth: the egg, larva (caterpillar), pupa (chrysalis) and the adult (imago). In the hot summer rainfall regions the new adults usually emerge in September and October and most species in the subtropical regions may fly year-round. The South-African butterflies are not migratory although they may move around for considerable distances.

The rarest butterfly in the world is the Palo Verde Blue Glaucopsyche lygadamus paloverdensis from a single site near Palo Verde southwest of Los Angeles in the USA. It was believed to have become extinct in 1983 but was rediscovered in 1994. Rare butterflies also occur in the United Kingdom, Mexico and the Far East. In South Africa, the Highveld Blue, Karkloof Blue and Brenton Blue are rare while the Waterberg Copper Eriksonia edgei has been rediscovered in the Bataleur Nature Reserve 25 km northwest of Bela Bela in 2013 where it now is a major tourist attraction. It was originally discovered in Ovamboland in Namibia and later in Zambia but Dave Edge found a colony in a small grassland area near Rankin’s Pass in 1980.

The butterflies in South Africa include 92 broad groups, most with several species and subspecies. The largest butterflies that may occur in the Waterberg include the White-barred Emperor Charaxes brutus natalensis, a tawny-orange butterfly with a prominent white medial band and a wingspan of up to 90 mm; the Variable Diadem Hypolimnas anthedon wahlbergi with black and white outer wings, yellow median rear patches and a wingspan of up to 90 mm; the Green-winged Emperor Charaxes candiope, an orange-red butterfly with green forewing green on the underside and a wingspan of up to 95 mm; The Forest King Emperor Charaxes xiphares, with a black upper side with white patches, a dark and royal blue spotted underside with orange edges and a wingspan of up to 95 mm; the Green-banded Swallowtail Papilio nireus lyaeus, a brownish butterfly with bright, silvery green-blue markings on a black background and a wingspan of up to 95 mm; the Blue-spotted Emperor Charaxes cithaeron cithaeron with indigo patches on a royal blue background and a wingspan of up to 95 mm, and the Large Blue Emporer Charaxes bohemani with prominent an indigo wing middle, medial white band and royal blue outer edges with two white spots and a wingspan of up to 100 mm.

As larvae, the butterflies feed on plant matter such as leaves, seeds or flower buds in an often specialized diet which can be one plant species only. This makes them vulnerable to habitat destruction and influences their distribution. Some of the larvae feed on blue-green algae that grow in symbiosis with fungi to form lichens. Other larvae feed on animal matter, such as young ants in a nest, while others feed on the regurgitated food of ants. Larval fat deposits are vital for the survival of those types of butterfly that do not feed as adults.

Those adults that do feed have a high energy demand and they feed on foods that are rich in sugar. Such foods commonly include nectar, fermenting fruit, the sap of trees and shrubs and the honeydew of aphids and scale insects. Other butterflies feed on the juices of carrion, some specializing on rotten prawns. They also feed on the faeces of mammals and birds, but especially on that of carnivores and by preference those of cats and primates. Butterflies have to drink water in hot weather and often swarm on river and pond banks. They derive essential minerals from puddles of the urine of mammals.

Butterflies are attractive prey for predators such as chameleons, birds and small mammals but they physically have few attributes to escape such predation. Larger butterflies, however, fly faster than birds such as swifts and swallows. However, most butterflies rely on cryptic colouration, deception or camouflage to avoid detection by predators. In some butterflies their colouration closely mimics the habitats in which they occur to such a degree as to become almost invisible. Others resembles dead leaves or inedible objects such as bird droppings. Still others have false eye spots in the tail which they can lose to a predator and still escape alive. Others have eye spots on the wings to attract attacks away from the head. The sudden opening of the wings to reveal eye spots also startles a predator and allows a butterfly to escape.

While butterflies cannot sting, many larvae and adults are distasteful and even poisonous to predators and they reflect this status by their colouration and markings. They become distasteful by feeding on toxic plants. Nevertheless, there are as many palatable types of butterfly as distasteful ones. Some palatable butterflies mimic distasteful ones, while distasteful types may also mimic each other.

Butterflies have colour vision and use their colour patterns to choose mates. Some males exude pheromones to attract females. Butterflies perform dance rituals as a prelude to mating, and may fly united while copulating. The sperm is carried by the female and is used to fertilize the eggs when laying them singly or in batches on an appropriate food plant.

The larvae hatch and undergo successive moults as they grow and their appearance is distinctive for a particular type of butterfly. Eventually the larvae pupate within larval shelters, some in a silken girdle or a cocoon. Through metamorphosis, the adult butterfly eventually emerges, usually early in the morning and when the environment is optimal for survival of the adults in terms of suitable food sources. By the pumping of the heart, the wing veins straighten and the harden into their final form to allow flight.

References:

Anon 2004. Butterfly fossils. www.crystalinks.com/fossilbutterfly.html

Anon 2011. Top 10 rarest butterflies in the world. www.johnmcnamara.hubpages.com

Anon 2013. Butterfly evolution www.en.wikipedia.org/wiki/Butterfly_evolution

Anon 2013. Butterflies in ancient Egypt. www.frontpage.swan.ac.uk/egypt/infosheetgen/butterflies_in_ancient_egypt.html

Woodhall, S 2005. Field guide to butterflies of South Africa. Cape Town: Struik Nature.

Article by Prof J du P Bothma

 

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