Butterfly Strategies

Butterflies, being day-flying, use eyesight to locate members of the opposite sex; moths have less acute vision and use their specialized antennae for mate-finding. Their antennae act as scent detectors and they can locate potential mates over distances of up to 15 kilometres!

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BUTTERFLIES IN PERSPECTIVE
Insects are one of the oldest life forms, evolving from the very earliest living creatures to leave the primordial seas some 400 million years ago. Some, notably the fishmoths and cockroaches, have remained almost unchanged for the last 360 million years.

The oldest known butterfly fossil is from Colorado and is approximately 60 million years old. Interestingly, this fossil is structurally identical to the butterflies of its family (the Libytheidae) which occur throughout the world today, showing that there has been little evolutionary change for a very long time. This in turn indicates that butterflies and moths must have evolved more than 60 million years ago at a time when huge dinosaurs ruled the planet. Unfortunately, these delicate creatures do not fossilize well, so their story is lost in the mists of time. Nevertheless, we know that these insects were around before the break-up of the continents.

For instance, the famous ghost moth Leto venus of the Tsitsikamma region has no relatives in Africa, but has many in Australia. The butterfly genus Brephidium, which in Africa contains only one species restricted to the Cape, is known only from one other area - Central America. These insects are tiny, are poor fliers, and are not given to travelling any distance from where they breed. The butterflies of tropical Africa and Madagascar have closer affinities to those of Asia than those of Europe, indicating a closer and more recent link between Africa and Asia than between Africa and Europe.

Insects and plants have evolved together, and understanding the relationship between them is vital to maintaining a healthy balance of life on this planet. Many insects have a very close link with certain species of plant, and without their help those plant species will, in time, become extinct. For example, ants such as the pugnacious ant Anaplolepsis custodiens are responsible for the regeneration of proteas: the seeds are pulled underground by the ants which eat off the edible food body, known as the elaiosome, leaving the seed 'planted' in a fertile ant midden, ready to germinate when conditions are favourable.

Insects also play a key role in the recycling of dead or waste material. The humble dung beetle, for example, ensures that dung, which would otherwise harden and smother plant matter, is broken down and recycled. Similarly, ants and flies are responsible for assisting in the decomposition and recycling of dead carcasses in the veld, and termites and beetles break down large items such as dead trees.

Butterflies and moths together form the Order Lepidoptera, which is the second largest insect order (after the beetles, or Coleoptera). The majority of the Lepidoptera are moths, with 65 families and approximately 130000 different species. By comparison, butterflies comprise 20000 species in 14 families. Nearly all butterflies are diurnal, whereas most moths are active at night. The reason for this is that the wings of butterflies are like miniature solar panels which have to be warmed by the sun. Moths, on the other hand, vibrate their wings for a period before flight in order to warm up their bodies.

The antennae of butterflies and moths also differ. Those of butterflies are club-shaped, whereas moth antennae are either straight and even, or feathery. Butterflies, being day-flying, use eyesight to locate members of the opposite sex; moths have less acute vision and use their specialized antennae for mate-finding. Their antennae act as scent detectors and they can locate potential mates over distances of up to 15 kilometres!

In many butterfly (and moth) species the markings of the male are quite different to those of the female; this is known as sexual dimorphism. This is carried a step further in some species where there are great differences between their summer and winter forms - a phenomenon known as seasonal dimorphism. In the case of the gaudy commodore Precis octavia, the seasonal differences are very marked indeed and the two forms use different habitats. The summer form prefers the tops of grassy ridges, and the winter form lives in sheltered wooded kloofs. In was only through captive breeding that taxonomists came to realize that the two forms were a single species.

BUTTERFLIES AND MOTHS - THEIR PLACE IN THE WORLD
Butterflies and moths, along with other insect pollinators such as bees, beetles and flies, play a vital role in maintaining plant communities. Sometimes this role can be a very specialized one.

One such case is that of the mountain pride butterfly Aeropetes tulbaghia. This butterfly has a well-documented predilection for red flowers, in particular those of the red-hot poker Kniphofia praecox. In 1895, the botanist Dr Rudolph Marloth discovered that the butterfly was the sole pollinator of another plant with red flowers, the magnificent red disa Disa uniflora. It has since been found that there are no fewer than 15 other fynbos plant species that are totally dependent upon this butterfly for pollination; all of these plants have large red flowers and bloom only from December to May, coinciding with the flight period of the butterfly. Some of the species concerned are the nerina Nerine sarniensis, the 'nuwejaarsblom' Gladiolus cardinalis, the George lily Cyrtanthus purpureus, the beautiful and very rare Bredasdorp lily Cyrtanthus guthrei, and the exquisite Disa ferruginea, a plant that produces no nectar and relies purely upon its red flowers to attract the butterfly. Without the butterfly, these fynbos plants would be doomed to certain extinction.

Although many insects are beneficial or essential in maintaining plant communities, others have a severe economic impact as crop pests. Obviously, a detailed knowledge of the life-cycles and habits of these insects is vital for their effective control. Only two indigenous butterflies are known to attack crops in South Africa. These are the lucerne butterfly Colias electo, whose larvae eat lucerne, and the citrus swallowtail Papilio demodocus, whose larvae feed on the leaves of citrus plants. Both butterflies tend to cause only minimal damage to these plants and also utilize many indigenous plants not cultivated by man. The accidental introduction of the European cabbage white butterfly Pieris brassica to the Western Cape does, however, change this picture considerably as the butterfly thrives on a number of cultivated crops such as cabbage, cauliflowers, beetroot, and nasturtiums.

THE KEYS TO SURVIVAL
Most butterflies and moths spend only a very short part of their total lives as adults. There are exceptions to this; for example, in North America, adult monarch butterflies Danaus plexippus live for a full 12 months, during which time they fly south to Mexico from their northern breeding grounds, hibernate near Mexico City for the winter, and then return to their breeding grounds in the spring. However, no southern African species is known to live in its adult form for much longer than a month, during which time mating takes place and eggs are laid. The remainder of the life-cycle is spent in the egg, larval (caterpillar), and pupal stages. Female butterflies can lay more than 100 eggs and mortality in these early stages of life is high. Each stage is attacked by different insect parasites, usually certain species of wasp or fly. The larvae are located by the parasite at an early stage; the parasite lays its eggs on the larva and its own larvae burrow into the host without killing it. The parasite larvae remain dormant until their host has grown sufficiently to provide a full-sized meal. At this stage they eat the host from within.

Those butterfly and moth species that sit out the unfavourable months in the pupal form use camouflage and immobility to survive. Species which hibernate in the larval stage employ a range of survival mechanisms. Some use only camouflage; among these are the high mountain Satyridae, or browns, whose larvae hibernate inside grass tussocks and can remain dormant for long periods and even survive total immersion under snow or water.

THE ANT CONNECTION
Roughly one third of all South African butterfly species depend on ants for their survival. Understanding this complex relationship is crucial to their conservation. In nearly all cases, the butterflies emerge once a year, and the larval stage lasts approximately 11 months, although in some the larval stage might last for several years. Newly-hatched or immature larvae are picked up by the ants and gently carried into the ants' nest. The larvae produce highly attractive chemicals from 'honey glands' or 'dew patches' along their backs, upon which the ants feed. The ants actively protect them at all times. The relationship is an extremely specific one, with certain ant species associating only with particular butterfly species.

The nature of this association varies considerably between different butterfly genera. In species of Aloeides, Poecilmitis, Spindasis and Aphnaeus, the larvae merely shelter with the ants, which escort them out of their nests at night to feed nearby. They always return to the ant nests, under escort, before dawn. In species of the genus Lepidochrysops, the larvae grow to the third instar on their own foodplants before the ants take them underground to their nests. Once the larvae are in the nest, they do not re-emerge until they are adults. The butterfly larvae in the nest become parasitic, feeding on the immature stages of their ant hosts.

In their adult form, butterflies use various techniques to ensure their survival. Many species are well camouflaged because even the fastest-flying butterflies, which can elude predators under warm conditions, are immobilized when it is cold, rendering them completely helpless. Predators could theoretically eat them at leisure - providing they could find them in the first place. This is why many butterflies with spectacular upperwing markings have cryptic underwings, enabling them to blend in with their surroundings when at rest.

POISON AND MIMICRY
Certain butterflies, notably from the Danaid and Acraeid families, have a different survival trick. These butterflies have relatively conspicuous larvae, and the adults themselves are brightly coloured and fly slowly; they are therefore relatively easy targets for attack. However, their larvae feed on plants which have toxic properties. These toxins are retained within the larvae, pupae and adults of these insects, and are used to deter attacks by predators. In the case of the very common garden acraea Acraea horta, the toxin utilized is cyanide, extracted from the leaves of its foodplant, the wild peach tree Kiggelaria africana.

Distasteful butterflies all tend to use combinations of red, black, yellow and white colours to advertise that they are noxious to bird, reptile and mammal predators. These warning patterns and colours are frequently imitated by other, palatable butterflies. This process is known as mimicry and is a mechanism for ensuring adult survival. Frequently it is only the females that mimic toxic species. One of the best examples of this is Papilio dardanus, whose females mimic no fewer than four different species from the Danaid family, with many intermediates. Females from Ethiopia are non-mimetic, resembling the males: the mimetic forms occur from Kenya southwards.

FLYING IN THE FACE OF EXTINCTION
The butterflies of the western and southern regions of the Cape have evolved in isolation, cut off from the rest of the continent by the uniqueness of their habitat. Butterfly colonies in these areas have become isolated from one another through their own very specialized requirements, as well as the rugged and mountainous terrain. This has led to the evolution of dozens of closely related species, the lycaenids. To date, no fewer than 190 butterfly species have been described which are endemic to the Cape; this amounts to approximately 30 per cent of all the known South African butterflies. Probably because of the long and harsh Cape winters, nearly all of these butterflies are ant-associated, and are therefore very specialized in their requirements. This has led to many of them being restricted to very small areas, and some face an imminent survival crisis.

The strandveld butterfly Oxchaeta dicksoni has no known subspecies, flies only during August and September, and was discovered fairly recently in a tennis-court sized locality near Melkbosstrand on the West Coast that was subsequently put to the plough. It was later rediscovered in an equally restricted locality near Mamre, where it still occurs today. However, this locality is becoming increasingly threatened by human habitation and alien infestation. The prospects for this insect appeared hopeless until two Natal Museum collectors found it hundreds of kilometres away at Witsand in September 1980. Witsand and Mamre are separated by mountainous terrain, quite unsuitable for this insect. Unfortunately Oxchaeta very quickly disappeared from its Witsand locality as a result of development.

We subsequently spent seven years trekking to this area during early spring in the hope of finding this elusive little insect. The whole area from Cape Infanta to Stilbaai was painstakingly covered, but without success. Finally, just when my wife's patience with the monotony of our family holidays was at breaking point, we found the insect, quite by chance. We now know of two colonies in this area, but neither is any larger than the original Melkbosstrand locality. Oxchaeta associates with the ant Crematogaster peringueyi, but so far all attempts at getting the larvae to feed in captivity have failed and the survival requirements of the insect remain a mystery. For species such as this, until we can unravel their life-histories, the only conservation hope lies in preserving the habitat in areas where they are known to occur.

There are other similar examples of highly localized and endangered butterflies in the south-western Cape in particular, such as the rare Table Mountain copper Argyrocupha malagrida malagrida, now confined to one small locality on Lion's Head in the Table Mountain range, and the much publicized Brenton blue Orachrysops niobe, threated with extinction in its last known habitat at Brenton-on-Sea in the Western Cape.

There is much we have still to learn from the insect world. Insects provide a window on the origins of life and its paths of evolution. Some have shown astonishing ability to adapt quickly to changing circumstances, and thereby afford us the opportunity of studying the process of evolution as it occurs.
Apart from their pivotal role in nature, there may be many as yet untapped secrets of the insect world that could prove of great economic benefit to man. It has recently been discovered that the venom from a bee sting can be utilized to destroy cancer cells in the human body: the venom attacks the cancer cells but leaves healthy cells intact. Having discovered this, scientists must now find a way to suspend the action of human antibodies for long enough to allow the venom to do its work.

It does not take much imagination to see that every insect species that becomes extinct could take with it unknown benefits to mankind.

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