杏吧原创

Many Christmas revellers in the dry interior of southern Africa, won鈥檛 be
carving up a turkey on the big day; instead they鈥檒l be feasting on the local
harvest of mopane worms. They may not look like much of a meal but there is a
surprising amount to recommend tucking in to these fat, spiny, mottled
creatures.

The so-called worms are actually caterpillars of the emperor moth,
Gonimbrasia belina. Their common name derives from the mopane tree,
Colophospermum mopane, where the moth spends most of its short life. In the
last century, Europeans reported the collection and consumption of the
caterpillars by local peoples, most adding that they found it a 鈥渇ilthy鈥�
practice. More dispassionate research has found that mopane worms make good
eating. 鈥淭hey are an incredibly important source of protein in a period when
there is very little other protein available,鈥� says Keith Leggett of the
Kalahari Conservation Society, which earlier this year, with the University of
Botswana, cosponsored a national symposium on mopane worms. The worms are also
considered key players in maintaining the ecological balance of their dry bush
habitat.

Both mopane worms and mopane trees are well adapted to their habitat, a
drought-ridden belt of dry bush crossing the African subcontinent from Namibia,
to Botswana, Zimbabwe and South Africa. In early November mopane trees put out
new leaves, regardless of whether the spring rains have started. Around this
time, the emperor moth emerges from its underground chrysalis and the life cycle
of the mopane worm begins. The moths lay their eggs, in clusters of 190, on the
young mopane leaves. In 18 days the tiny larvae, just 6 millimetres long, hatch
out. In five moults over the next five to six weeks they reach sausage-like
proportions鈥�10 centimetres long and a plump 15 grams. By Christmas, 鈥檛is
the season to be harvesting them. A second generation, from eggs laid in early
February, can be harvested in April.

Weighty worms

The Council for Scientific and Industrial Relations, a governmental body in
South Africa, has analysed the caterpillars and found that they are high in
crude protein, 65 per cent of their dry weight. One hundred grams of dried
mopane worm provide 76 per cent of an average human adult鈥檚 daily protein
requirement and 100 per cent of the daily requirement of many vital vitamins and
minerals. Recent research has found that in terms of protein, fat, vitamins and
calories, the caterpillars compare favourably to meat and fish. The council
reported that 鈥渢he consumption of mopane caterpillars can, to a substantial
degree, supplement the predominantly cereal diet鈥� of rural Africans. This is
despite a certain degree of indigestibility, mainly due to their insect
exoskeleton of fibrous chitin.

Every December rural African women gather for the annual harvest. From
sunrise to sunset for five to six weeks they pluck the worms from the leaves and
gut them by hand. In the evenings they boil them and then set them out to dry.
Methods vary by region: In Venda, along the northern border of South Africa, the
worms 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 peanut shells to the uninitiated. But
they are popular, and are widely sold in small plastic packets in shops,
by the tin cupful at rural bus stops and by the kilogram in rural cooperatives.
They can be eaten dry, like crisps, or they can be rehydrated and served up in a
stew or simply fried.

Traditionally, the harvesting, processing and sale of mopane worms has been
informal and relatively small scale, with no controls, restrictions, rules or
regulations. But in recent years the worm trade has gained a more commercial
edge. Most mopane worms are exported to South Africa, where marketing surveys
put the annual mopane worm market at tens of thousands of tonnes, with the worms
fetching as much as 拢15 per kilogram in urban areas, though a more typical
rural price is about 拢3 per kilogram. As comsumer demand for mopane worms
increases, there are growing concerns about whether the caterpillars can keep
pace with the demand. Mopane worm populations have disappeared from parts of
Botswana after heavy harvesting and no one knows if they will recover; in
Zimbabwe, the local press has carried complaints of mopane worm 鈥減oaching鈥� and
reports of armed gangs robbing rural women of their worm harvest.

For more than five years Chris Styles, an applied ecologist at the University
of Pretoria, has been conducting a wide-ranging study of mopane veld ecology
concentrated in South Africa鈥檚 Northern Province. He stresses that we are 鈥渘ot
necessarily sure that utilisation is indeed sustainable鈥�, having witnessed a
population crash in 1993 caused by a combination of drought and
overharvesting. According to Styles, 鈥淲e鈥檙e going out there and
allowing harvesting over a given area, but no work has been done on ecology or
on population dynamics, and that鈥檚 absolutely imperative before one can make
inferences as to what sustainable utilisation levels are.鈥�

According to Styles, overharvesting could have long term implications, not
only for mopane worm populations, but also for land use. Mopane trees cover vast
areas of southern Africa, in dense and relatively infertile thicket. Once kept
in check by large mammals such as elephant and rhinoceros, some scientists
believe that mopane veld has advanced as these mammals have retreated into
national parks and game reserves. The task of holding the line against mopane
veld encroachment has fallen to the lowly caterpillar. Styles even suggests
that, in terms of impact on habitat, mopane worms could be more powerful agents
than elephants where the two coexist.

In his study area, a 4000-hectare farm near Pretoria, he found its 19 million
mopane worms consumed 873 tonnes dry weight of mopane leaf material, and
excreted 690 tonnes of dung in the course of their six-week lives. Styles
estimated that the study area could support 14 mature elephants, and that 27 per
cent of what the elephants ate they would browse from trees. He then calculated
that in the course of one year the elephants would consume only 83 tonnes dry
weight of mopane leaves, and would produce a total of 179 tonnes dung. 鈥淚n just
six weeks mopane worms consume 10.55 times more leaf material than the elephants
could put away annually, and the mopane worms produced 3.88 times more dung,鈥�
says Styles. 鈥淚n areas of mopane veld where the two species coexist, mopane
worms ought to be viewed over elephants as being the keystone species. 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.鈥�

Styles does not oppose commercial exploitation of mopane worms鈥攊n fact,
he is only too aware that it is an important source of revenue for the rural
poor. But he says that it must be done with care. One idea being studied by the
Industrial Development Corporation, a government think-tank based near
Johannesburg, envisages a form of domestication. The plan would be to breed
mopane worms under controlled conditions at a central station, then release them
on selected farms and communal lands to be harvested by traditional methods.
This would ease the pressure on the natural worm populations.

鈥淚 wouldn鈥檛 exactly say it鈥檚 going to become a major new food, quite
honestly,鈥� says Styles, conceding that many people are put off by the
worms鈥� texture and taste. But he recently had a request for more information
from a Belgian food importer interested in coating the worms in chocolate. 鈥淟ike
chocolate covered bees, that鈥檚 what the chap said to me,鈥� Styles commented. 鈥淗e
has a massive market for chocolate-coated bees.鈥�

But anyone who has eaten mopane worms, dried, canned, disguised in a hot
chilli stew or even stewed in white wine with a mushroom cream sauce, must
suspect its future as a food fad is remote at best. The most important
consumption of the worms will surely remain in southern Africa, with its growing
population, periodic drought and chronic shortages of affordable foods. The
mopane worm will remain a staple, Styles says, as long as supply can keep pace
with demand.