Mopane worm

Appearance

The moths are large with a wingspan of 120 mm. Wings are fawn coloured through shades of green and brown to red, with two black and white bands isolating the eyespots. An orange eyespot is present on each hindwing. Males moths have feathery antennae, which are used to find a mate. Larvae are black, peppered with round scales in indistinct alternating whitish green and yellow bands, and armed with short black or reddish spines covered in fine white hairs.

Naming

Mopane worms are an important source of protein for many in the region. The species was first described by John O. Westwood in 1849.

Behavior

Larvae eat a wide range of plants including mopane, "Carissa grandiflora", "Diospyros", "Ficus", "Rhus", "Sclerocarya caffra", "Terminalia" and "Trema". Mopane worm outbreaks defoliate shrubs, depriving game of browse.Like most caterpillars, the mopane worm's life cycle starts when it hatches in the summer, after which it proceeds to eat the foliage in its immediate vicinity. As the larva grows, it moults four times in its five larval stages, after which the mopane worm is considered most desirable for harvesting. Provided that the larva has not been harvested after its fourth moult, it burrows underground to pupate, the stage at which it undergoes complete transformation to become the adult moth. This stage happens over winter, for a duration of 6 to 7 months, whereafter it emerges at the beginning of summer.

The adult moths live only for three to four days, during which time they mate and lay their eggs.

Habitat

Widespread. Very common in semi-desert, bushveld and grassland.

Food

Although the mopane worm feeds chiefly on the mopane tree, it is not limited to this diet, and can feed on many other trees that are indigenous to the same regions, including the leaves of the mango tree. Thus the mopane worm is scattered over a fairly large area. As the larval stage of the mopane worm is fairly short, in contrast to other browsing caterpillars, the extensive damage to foliage is easily survived by the tree, in time to be replenished for the next generation of mopane worms. Like most caterpillars, the mopane worm is a voracious eater, and will continue to eat - almost non-stop - until it reaches the next stage of its life cycle, when it burrows underground to undergo metamorphosis.Mopane worms are hand picked in the wild, often by women and children. In the bush, the caterpillars are not considered to belong to the landowner, but around a house, permission should be sought from the resident. Chavanduka describes women in Zimbabwe tying a piece of bark to particular trees to establish ownership, or moving the young caterpillars to trees nearer home. When the caterpillar has been picked, it is pinched at the tail end to rupture the innards. The picker then squeezes it like a tube of toothpaste or lengthwise like a concertina, and whips it to expel the slimy, green contents of the gut.

Predators

Like many animals lower down on the food chain, the mopane worms and their eggs often fall prey to various predators as well as disease. Often, more than 40% of a mopane worm's eggs will be attacked by various parasites, and the caterpillars themselves are susceptible to infection from a virus that has a high mortality rate. The worms' main predators are various birds and humans, which rely on the caterpillars for sustenance.

Defense

Traditionally, mopane worms were harvested for subsistence. Because of the seasonal nature of the occurrence of these edible caterpillars, they are not a year-round food source. However, traditional mopane worm harvesting is evolving to be more commercially driven.

Since the 1950s, commercial farming methods have been applied to the mopane worm harvests, particularly in South Africa. Collectors may organise teams of hundreds of people to hand pick the caterpillars from the trees, after which they are bagged "en masse", weighed, and sent off to be processed. Owners of land where mopane worms are found may charge harvesters large fees to enter. Whereas this relationship profits both the commercial harvester and the farmer, it is often to the detriment of the local community for whom the caterpillars may previously have been an important source of food and seasonal income.