After the first good rains from December to February they suddenly appear – in their hundreds. They are seen especially in places where strong sources of light remain switched on all night. For just a few days each year, travellers at Hosea Kutako International Airport east of Windhoek are amazed by the large, mostly white and grey moths which are sitting everywhere on the outside of the building. Their wings measure 6.5 to 9.5 centimetres. Both the front and the rear wings have a grey-brown pattern and a brownish-yellow jagged line. Each of the front wings bears a so-called eye, a circular mark that resembles an eye to scare off predators. In the rainy season the striking western marbled emperor moth (Heniocha dyops) is a typical occurrence for a very short period of time.
During the few days of their moth life the males are looking to mate with the slightly larger females. They are attracted by the females’ pheromones (scents). Both genders of this nocturnal species are particularly attracted by strong sources of light.
After mating, the females look for a species-specific forage plant, mainly the black thorn (Acacia mellifera), and deposit their eggs in rows of six to ten. The tiny caterpillars hatch after just a few days and then eat continuously until they have grown to a length of about 6.5 cm. The quite colourful but nevertheless well-camouflaged caterpillars are fully developed in March or April, when they pupate in the ground where they turn into moths during the next few months. Come December to February, the next generation of adult western marbled emperors hatches after the first good rains and a new cycle begins. Moths and caterpillars are a protein-rich food for countless animals.
According to moth expert Dr Rolf Oberprieler the caterpillars pupate in the ground at a depth of about 10 cm, but it always depends on the condition and the moisture of the soil. The caterpillars bury deeper in soft, moist sand. Dr Oberprieler attended the DHPS in Windhoek, studied and worked in Pretoria and now lives in Australia. In 1995 he published the reference book The Emperor Moths of Namibia and is currently working on a “larger book”.
In some years there are so many caterpillars that they strip entire bushes down to the last leaf. Although the black thorn, or hook thorn acacia, is their main source of food, caterpillars are sometimes found on the mountain thorn (Acacia hereroensis) and the blue thorn (Acacia erubescens) as well.
In Namibia the western marbled emperor, colloquially dubbed the hakkie moth, occurs from Keetmanshoop in the south to Etosha National Park and the Kavango regions in the north and to Gobabis in the east. Dr Oberprieler says that they are particularly common around Windhoek and Otjiwarongo. They belong to the order Lepidoptera and the family Saturniidae. There are 27 species of emperor moths in Namibia.
Author: Dirk Heinrich