The return of the silk moth

The Prussian King Frederick II hoped to avoid dependence on expensive imports from China by producing silk domestically. With a royal decree and a donation of 330 mulberry trees, silkworm breeding began in 1744 and raw silk was actually produced. However, after initial successes, disease and adverse climatic conditions led to a slump in yields, with the result that silk production was completely discontinued in 1805. 213 years later, in 2018, Cornelia Jäger succeeded in hatching silkworms once again. As part of the environmental education programme in the plant garden, children can witness the growth and transformation from egg to butterfly.

As part of the environmental education programme in the plant garden, children were able to witness the growth and transformation from egg to butterfly.

After hatching, the little caterpillars were very hungry. Fortunately, there are still four mulberry trees on the grounds of the Francke Foundations. Several times a day, the caterpillars were fed fresh mulberry leaves so that they could grow and pupate after about a month – because hungry caterpillars devour huge amounts of food. Thanks to regular feeding and consistent climatic conditions, the caterpillars grew rapidly. After four to five weeks, the silkworms were large enough. They began to spin their silk thread and pupate in their cocoons. The children had built frames to help the caterpillars pupate.

The children had to wait three weeks before they could marvel at the miracle of metamorphosis: the first butterflies ventured out into the daylight and emerged from their cocoons. They fought their way out through a tiny hole in the cocoon, which they had created with a corrosive intestinal fluid. As soon as their heads had passed through the hole, everything happened very quickly and the silkworm moths emerged as butterflies. Immediately after hatching, the butterflies still seemed quite dazed. They did not fly at all. They waited for their mates to begin mating. The mating of the silkworm moths took several hours. Can you tell the females apart from the males? The children in the school garden had their own theory: ‘The females are fatter,’ they concluded. This seems logical, especially when the females are about to lay their eggs. A single silkworm moth female lays between 400 and 500 eggs. Shortly after laying their eggs, the moths die.

The history of silk production in Prussia

At the beginning of the 18th century, the art of silk cultivation, which originated in China, came to Prussia with the Huguenots. The cultivation of silkworms was soon regarded as a magic formula to combat the Prussian foreign trade deficit and to balance the national budget. The Prussian king therefore ordered that mulberry trees be planted all over the country to raise myriads of hungry caterpillars, from whose cocoons valuable silk threads were then to be extracted. On 17 February 1744, Frederick II (1712-1786) also ordered the Halle orphanage to establish a mulberry plantation for silkworm breeding »for the establishment and proper cultivation of which the orphans' children are to be used and constantly guided [...]«. Under the director Gotthilf August Francke (1696-1769), a nursery with over 4,600 larger and 15,000 young mulberry trees was established over the next two years on the site of today's high-rise buildings in Voßstraße. For the silkworms can only be fed with their leaves. The archives contain many records on this topical subject of the 18th century, including drawings and historical specialist literature. Three years later, the production of raw silk began here. In 1805, silk production had to be stopped due to adverse climatic conditions throughout Prussia. Silkworms are sensitive and actually at home in warmer regions.