South Africa is home to many rare species of beetle that need special protection and conservation
Sheree Russouw
When asked what God’s design pattern for organic revolution revealed, biologist JBS Haldane, simply said: “An inordinate fondness for beetles.” One fifth of all macrofauna are beetles, and it is estimated that there are 200-million beetles for every living person on Earth. Some entomologists suggest that if all the species of plants and animals were randomly lined up, every fifth one would be a beetle. It seems that beetles have wholeheartedly subscribed to the injunction: “Be fruitful, multiply and replenish the Earth.”
“Considering that beetles (Coleoptera) are represented by more than 350 000 known species, it is not surprising that they attract so much interest. They are to be found all over the world,” says Dr Ferdy de Moor, an entomologist at the Albany Science Museum.
“They play a role in the functioning of virtually every known ecosystem. Except for the ocean, beetles have developed numerous specialisations for coping with the challenges posed by every imaginable ecosystem. Beetles dominate every aspect of life on Earth. At about 10-billion individuals for every square kilometre they surely present an extremely successful group of animals.”
From the time he was a young and enthusiastic entomologist at Zimbabwe’s Bulawayo Museum, De Moor says beetles have fascinated him because of their remarkable adaptations to life in aquatic and terrestrial ecosystems. “They have specialised together with man and his crops in making use of the abundance of food crops produced. There are pest species that eat what is produced, whereas beneficial species are often used as biological control agents removing unwanted problems and controlling problem plants and waste products such as bovine dung in Australia,” he says.
In ancient Egypt the dung beetle was regarded as sacrosanct. J Henri Fabre, the 19th century entomologist, wrote about the feeding frenzy of dung beetles. “Before the sun becomes too hot, they are there in their hundreds, large and small, of every sort, shape and size, hastening to carve themselves a slice of the common cake.”
De Moor says that some species of dung beetle collect dung from herbivores and bury it immediately underneath the dropping. Others gather a large ball and roll this to a suitable site, where a nest is dug and the ball of dung buried underground with an egg in it. Here, the dungbeetle larva develop and feed on the dung.
“Many beetles bore in wood and serve to break down the hard tissues, recycling the nutrients back into the ecosystem. As predators, scavengers, browsers, grazers and detritivores, beetles feed on living and dead plant matter. They clean up ecosystems by burying dung and picking clean carcasses of dead animals,” De Moor says.
Confusion often arises when people mistakenly believe that some bugs are beetles. “The Christmas beetle is actually a bug and not a beetle at all. Bugs have a fundamentally different life cycle. They develop from the egg through a series of nymphal stages that closely resemble each other and then they finally attain the adult stage,” he says.
Beetles have a complete life cycle comprising an egg; several larval stages; and a resting pupal stage, which then metamorphoses into the adult beetle. “The larval stages are very different to the nymph stage of bugs in that they do not at all resemble the adult. So we do get baby bugs but not baby beetles.”
He says that you can identify adult beetles by the presence of a pair of hardened wing covers. These have folded membranous wings tucked underneath. The mouthparts of beetles are mandibulate with a pair of chewing, grinding jaws, but the mouthparts of bugs are modified into a sucking proboscis.
De Moor says beetles are attracted to the opposite sex by pheromones. With their sex drive in full throttle, beetles can mate a number of times, although some species mate and remain together looking after the larvae. Other species congregate in a tree or around some attractive object and thus enhance the chances of meeting mates. The larval stage of beetles can last from a few weeks to several years and the adult can live for several years.
The size of adult beetles ranges from less than half a millimetre to 16cm in some of the large rhino beetles from South America. The Hercules beetle, which makes its home in the rain forests of Central America, has two enormous curved horns. Indeed, this dinosaur-looking beetle can fly.
“It is interesting to study the fossil history of beetles what were they doing when the dinosaurs roamed the Earth? Records of beetles go back 270-million years, long before dinosaurs dominated the Earth,” he says.
There are about 15 000 species of beetles in southern Africa. “A single family of beetles, the Scarabaeidae, are comprised of the dung beetles, rhino beetles, cockchafers, rose beetles, fruit and flowerchafers and goliath beetles. All these beetles are related but show a vast array of adaptations to various modes of existence. There are about 2 000 species in this family.
“A number of beetle families have adapted to life in fresh water. These families of beetles display an array of adaptations for coping with the challenges posed by living in water. The common names of these families often indicate some main features of their behaviour, for example, swimming beetles, diving beetles, marsh beetles, long-toed beetles and whirlygig beetles. There are many unique species of beetle in South Africa and some are very rare and deserve special conservation and protection.”
Beetles employ strange self-defence mechanisms. The predatory bombardier beetle ejects an explosive mixture of hydroquinone, hydrogen peroxide and a potent catalyst from its anus. This mixture can reach temperatures of up to 100C and wards off predators and overly enthusiastic humans. The active ingredient of Spanish fly, the supposed aphrodisiac, is made from the crushed bodies of blister beetles. This chemical, cantharidin, causes severe irritation and blistering of skin. De Moor says that click beetles are able to deter predators by flicking their abdomen with a loud click and bouncing out of the way.
Flight and rapid running are also handy escape modes, but some beetles are flightless and have undeveloped hind wings. Unlike other insects, beetles have a pair of leathery protective wings called elytra that cover their membranous flight wings. During flight, the aerial masters spread the elytra apart and the two flight wings are unfolded and extended.
De Moor emphasises the importance of beetles. “It is important to get people interested in insects as they are a very important functional component of our everyday existence. The beneficial and heuristic value of getting to know more about beetles is vast. They teach us about so many principles and concepts and get people to think and ask questions.
“Insects fill the middle link in the trophic ecology level. If man had the power to exterminate all insects and was also so short-sighted that he achieved this, the world as we know it would cease to exist. Humanity would follow shortly after in the line of extinction,” he says.
Dr Ferdy de Moor and Helen James will present a workshop on beetles at the Albany Science Museum on March 14, 15, 18 and 19