An insect that has been bred for over 4,000 years and produces products such as clothing, food, cosmetics, and pharmaceuticals—what comes to mind when you hear that? You might immediately think of clothing. That's right, the insect's name is the silkworm. It's an insect that produces silk thread, which is the raw material for silk fabrics such as silk scarves. In addition to being used as a fiber, silk is processed into powder or liquid and used in food and cosmetics, and is also used in the medical field as surgical sutures.


Silkworm adults and cocoons
Silkworms play a vital role in people's lives, but how many people have actually seen one? In recent years, sericulture in Japan has been in decline due to the rise of inexpensive synthetic fibers, so they may not be a common insect. However, in the early Showa period, about 40% of all farmers raised silkworms as a side business, so some people may have had silkworms raised at their parents' or grandparents' homes.

Many people see them as products but have never seen them alive, so we have an exhibit at Insectarium in Tama Zoo. On display are slightly larger larvae and cocoons. If you're lucky, you might even see the adults. The reason we display larger larvae is that newly hatched larvae are extremely small and probably wouldn't be visible if they were on display.

Newly hatched larvae are called "kego" and are less than 2mm long. They eat voraciously and grow, reaching about 60mm in length after approximately 25 days, and their weight increases to about 15,000 times their size immediately after hatching.


Fifth instar larva and first instar larva
While some people may dislike the caterpillar-like appearance of butterfly and moth larvae, silkworm larvae are something that even those who are squeamish about caterpillars should try to touch. The large larvae have plump, smooth bodies that feel just like silk. The texture is similar to a baby's upper arm, and you might find yourself addicted to touching them after just one try. Once the COVID-19 situation calms down, we are thinking of offering visitors the opportunity to touch them at events and other occasions.

Furthermore, the adults are white and covered in fluffy fur, giving them a cute appearance. Watching them groom their antennae with their front legs is reminiscent of a hamster grooming itself.


Cute-faced, fuzzy adult insect
In Hino City, where Tama Zoo is located, sericulture once flourished, and in the neighboring city of Hachioji, it was a vital transportation hub as a stopover point on the "Silk Road," Japan's version of the Silk Road, connecting the Kanto region to Yokohama Port. Due to this history, some elementary schools in Hino City and Hachioji City even raise silkworms as part of their curriculum. Silkworms are fed mulberry leaves, but they can also be raised on artificial feed and grow quickly, making them perfect for learning about insects. Furthermore, there is much to learn from their cultural and industrial history, which will surely be beneficial for children's education.

Silkworms are not only used in products such as silk fabrics, but they are also pleasing to the eye, pleasant to touch, and enjoyable to raise. We hope you will feel closer to silkworms, which are so useful in people's lives.

[Tama Zoo]

(January 8, 2021)