The mopane caterpillar is a dietary staple for many people – and a vital agent in keeping the veld healthy, writes Ellen Bartlett
THE larva of Gonimbrasia belina, the emperor moth, is fat and spiny and mottled black and gray. It does not immediately spring to mind as food.But G belina, better known as the lowly mopane worm, is more than a gimmick to grace the starters menu at Johannesburg’s Gramadoelas restaurant. For many rural people, it is a delicacy and dietary staple.
“It’s an incredibly important source of protein in a period when there is very little other protein available,” said Keith Leggett of the Kalahari Conservation Society, which last year co-sponsored with the University of Botswana a national symposium on “phane”. “They come in at a time when there is very little else to eat.”
European explorers and early settlers to Southern Africa described the collection and consumption of the caterpillars, many adding that they found it a “filthy” practice. More dispassionate research since then has found that mopane worms not only are good eating from a nutritional standpoint but they also may be key to maintaining the ecological balance of the dry bush they inhabit.
The worm’s common name derives from the mopane tree, Colophospermum mopane, on which the emperor moth lives for most of its short life. Both the mopane worm and tree are well-suited to their habitat, the belt of dry bush crossing the subcontinent from Namibia, across Botswana, Zimbabwe and South Africa, to Mozambique.
Neither is dependent on the rainy season to come to life. In early November, whether the spring rains have started or not, the mopane tree puts out new leaves. And the life cycle of the mopane worm begins with the emergence from underground of the emperor moth.
The moths lay their eggs, in clusters of 190, on the young mopane leaves. In 18 days, the tiny larvae emerge, just 6mm long. In five moults, over the course of five to six weeks, they reach sausage-like proportions – 10cm long and a plump 15g.
The first generation is harvested around the end of December. A second generation, from eggs laid in early February, is harvested in April. The Council for Scientific and Industrial Research has analysed the caterpillars and found them to contain high amounts of crude protein,65% on a dry mass basis.
One hundred grams of dried mopane worm provide 76% of the average individual’s daily protein requirement and 100% of the daily requirement of many vitamins and minerals. In terms of protein, fat, vitamins and calories, the caterpillars compare favourably to meat and fish. Despite a certain degree of indigestibility – like any living thing with an exo- skeleton, mopane worms contain large amounts of crunchy chitin – the council reported that “the consumption of mopane caterpillars can to a substantial degree supplement the predominantly cereal diet” of rural people.
Thus every December and every April rural women gather for the harvest. From sunrise to sunset for five to six weeks they pluck the worms from the leaves and then gut them by hand. In the evenings they boil them and set them out to dry.
Methods vary: in Venda, the caterpillars are dried and smoked in ash and hot coals; in Botswana they are boiled in salt water and then sun-dried. The end product looks like blackened peanuts, curled and dry, and about as palatable as the peanut shells. They are sold in small plastic packets in shops, by the kilogram in rural cooperatives, by the tin cupful at rural bus stops. They can be eaten dry, like hard crisps, or they can be rehydrated, served up in a stew or fried.
Traditionally, the harvesting, processing and sale of mopane worms has been strictly informal, no controls, restrictions, rules or regulations. In recent years trade in mopane worms has turned increasingly commercial. South Africa is the region’s big consumer of mopane worms. Worms harvested in other countries are imported here. Marketing surveys have found the mopane worm market to be in the tens of thousands of tonnes, with the worms fetching as much as R105 a kilo in urban areas, though a more typical rural price is about R20.
But as interest in the mopane worms’ commercial potential increases, there is concern about whether the caterpillars can keep up with the demand. Mopane worms have disappeared from parts of Botswana after heavy harvesting; in Zimbabwe there have been complaints of mopane worm “poaching,” and reports of armed gangs robbing rural woman of their worm harvest.
Chris Styles, an applied ecologist who conducted a wide-ranging study of mopane worms in the Northern Province, found himself witnessing a population crash caused by a combination of over-harvesting by local women and drought.
“One is not necessarily sure that utilisation is indeed sustainable,” Styles said. “We’re going out there and allowing harvesting over a given area, but no work has been done on ecology, on population dynamics, and that’s absolutely imperative before one can make inferences as to what sustainable utilisation levels are.” According to Styles, over-harvesting could have long-term implications not only for the mopane worm population, but also for land use.
Mopane veld covers vast areas of southern Africa. Dense, impassable and relatively infertile thicket, it was historically kept in check by large mammals such as elephant and rhinoceros, according to some scientists. But as the large mammals have retreated into national parks and game reserves, the mopane veld has advanced. The job of holding the line against mopane veld encroachment has fallen to the lowly caterpillar.
Styles has gone so far as to suggest that, in terms of impact on habitat, in places where they co-exist mopane worms are more powerful agents of change than elephants. In his study area, a 4 000ha farm, he found the mopane worm population consumed 873 tons dry mass of mopane leaf material, and excreted 690 tons, in the course of their short lives.
Estimating that the study area could support 14 elephants, and that 27% of what the elephants ate they would browse from trees, he reported that in the course of an entire year the elephants would consume only 83 tons dry mass of mopane leaves, and would produce a total of 179 tons of dung.
“In areas of mopane veld where the two species co-exist, mopane worms ought to be viewed over elephants as being the keystone species,” Styles said. “There is no doubt about it, the impact they have is enormous, so if you remove them you are definitely interfering with the ecology of the area.”
Styles does not oppose commercial exploitation of mopane – in fact, he points out that it is an important source of revenue for the rural poor.
He merely cautions that it must be done with care.
One idea studied by the Industrial Development Corporation was to domesticate them, after a fashion. The plan would be to breed them under controlled conditions at a central breeding station, then release them into the wild at selected sites.
One prospect protectors of the mopane worm need not fear is that the worm will become some kind of culinary trend, like the truffle, though Styles did recently receive a request for more information from a food importer in Belgium who was interested in chocolate-coating them.
“Like chocolate-covered bees, that’s what the chap said to me,” Styles said. “He has a massive market for chocolate-coated bees.”