Silkworms and Samurai: How Butterflies Shaped Modern Science in Japan

The silkworm (Bombyx mori), bringing you science since the Edo period

Before coming to Japan I didn’t know anything about the history of science in Asia.    Luckily, the fellowship program I’m brought in a guest speaker, Dr. Kaori Iida, to give the American students a crash course in Japanese scientific history.  Dr. Iida did her PhD in genetics at Pennsylvania State University, but one of her interests is the history of biology in Japan.  One of the big surprises from her talk was that silkworms (which are butterflies, well,  moths to be exact) played a big role in developing science in Japan, which led me to read more about the history of sericulture (raising silkworms).   Silkworms (Bombyx mori) produce silk when they spin their cocoons and this silk fiber can be re-processed into silk thread and woven into silk cloth.  More importantly, they were one of the first subjects of rigorous biological study in Japan.

To give you an idea of how silkworms shaped science in Japan, I have to take you back to the early 1800s when Japan was still a feudal nation. Japan had had some contact with the outside world back in the 1500s, but in 1633 it decided that it didn’t like how it was being treated by western powers.  So it shut it’s borders and cut off almost all contact with the outside world. During this time Japan was developing its arts and literature, but science was still a pretty informal job. The Japanese were great at breeding plants and animals, and understood how to select for unique traits.  However most people doing science at the time didn’t consider themselves scientists, they thought of themselves as farmers or breeders.  One of the best examples of this is silkworm breeding. Japanese silk merchants knew a lot about how to breed silkworms, and had done lots of experiments to refine silk production, but they were doing it in a decentralized way rather than as a scientific community.  In fact, lots of the silk producing families were trying to select silk worms to produce unique lines that would make their silk a recognizable “brand” ,and they didn’t want to share their trade secrets.

Print of women raising silkworms. Actually, raising caterpillars hasn't changed much in the last 200 years and Jess and I use a similar method to the one depicted in the painting. We collect eggs (bottom right panel) and then raise caterpillars in bins filled with leaves (upper and lower left panels).

Feudal japan in the 1800s was a lot like feudal Europe: most people were peasants living in rural areas. If you were lucky, however, you were born a samurai (who were like noblemen/knight/poet/bureaucrats) and the government paid you to live in an awesome castle, tax your peasants, and keep order. You also had the right to strike down any commoner who didn’t show you respect and had the right to carry awesome swords.  The man in charge of feudal Japan was called Shogun. There was an Emperor as well, but he was basically a figurehead and was kept in isolation away from the public.  The laws of the Shogun stated that he couldn’t even leave the palace unless there was an emergency.  The emperor lived in Kyoto, while the Shogun ran the show up in Tokyo.


Everything started to change when the American navy arrived in 1853, and decided that they were going to trade with Japan whether Japan liked it or not.  Commodore Matthew Perry got down to business doing what colonial powers do best, and he forced Japan to sign what are now called the “Unequal Treaties” (which I think are pretty self-explanatory). Perry’s arrival upset the status quo in a number of ways.  The Japanese were dismayed to learn that they were going to be basically giving away all their trade goods to the United States.  If that wasn’t bad enough, when they saw Perry’s modern ships they suddenly realized that they were missing out on the technological advances of the rest of the world.  So in 1868 they decided to rebel and kick the Shogun and his isolationist policies out, and installed the Emperor on the throne.

Japanese painting of Commodore Perry's ships. While the ship clearly didn't have a gaping mouth and eyes, I think this painting captures the general feeling of "Oh crap..." that swept Japan after contact with the United States.

Being ruled by an Emperor doesn’t sound very different from being ruled by the Shogun, but Emperor Meiji and his government were actually really eager to interact with the rest of the world.  They were also very committed to promoting science and technology in Japan.   Within a few years they  had set up  new universities and started hiring foreign instructors to expose students to new ideas. They started using western clocks to tell time and got everyone using a western calendar, so that the Japanese could more easily do business with other countries. They set up a European style parliament, and gave all male citizens the right to vote (women got the vote in 1946). They also felt that all the samurai antics were a distraction from the business of modernizing Japan, so they gave the samurai a huge pay cut and stripped them of their special privileges. It was a pretty crazy time in Japan, the economy was in turmoil, people violently disagreed with each other about whether to support the Shogun or the Emperor, and unemployed samurai were roaming around the countryside causing havoc.

The Meiji Emperor observing parliament from the balcony on the left (image:MIT archives)

So you’re probably asking where the butterflies and science come in.  Well, one of Japan’s major exports was silk, and just as the Meiji Revolution was taking place, a terrible epidemic of silkworm diseases  struck Europe.  Japan, being isolated, escaped the epidemic and the price of Japanese silk skyrocketed.  Japan’s new economy meant it could re-negotiate it’s unequal treaties and gain back power.

The Meiji government realized the importance of silk production in getting the new economy up to speed, and by 1890 they had set up 300  agricultural  research and extension centers to study silkworms and to train and license silkworm breeders.   Another big advance was the introduction of “Mendelism” to Japan, and scientists from the agricultural stations began to educate silkworm breeders about basic genetics.   In just a few decades, breeding silk worms went from being a trade practiced by merchants and craftsman to a scientific discipline with university research programs dedicated to it.  All that silkworm research later provided the foundation for Japanese genetics and biology all the way up through the present day.

women feeding silkworms in 1904

Although Emperor Meiji is considered one of the great promoters of science in Japan, as a butterfly scientist, I think it is important remember that the silkworm played a small but important role in the process too.  If you’d like to learn more about silk worms and the history of science in Japan here is a paper by Dr. Lisa Onaga, and a paper on the later development  of genetics in Japan by Dr. Iida.

Onaga, L.  Toyama Kametaro and Vernon Kellogg: Silkworm Inheritance Experiments in Japan, Siam, and the United States, 1900-1912. Journal of the History of Biology (2010) 43:215–264

Iida, K.  Practice and Politics in Japanese Science: Hitoshi Kihara and the Formation of a Genetics Discipline. Journal of the History of Biology (2010) 43:529–570

Butterfly Tourism

One of the many fun things about Japan has been learning about the research that my labmates are doing.    Last weekend, my labmate Suzuki-san invited me to come see the study species he used for his masters degree.  There was a regional ecology conference in a town outside Kyoto called Nara, and Suzuki-san and I went to get dinner with some of the professors who were in town for the meeting.  Since I don’t speak Japanese and couldn’t understand any of the talks, we decided do a little sight-seeing around Nara instead of going to the conference.  We also checked on Suzuki-san’s old field site on the way, to see how his butterfly is doing.  Luckily his field site is in a town just a few train stops outside of Nara, so it was easy to drop by for a quick visit.  One great thing I’ll really miss about Japan is being able to use public transportation for research!

Suzuki-san did his masters on the endangered butterfly Ypthima multistriata, which is only found in a small area of Kansai, Japan (Kansai is the area surrounding Kyoto, and includes the cities of Osaka, Nara,  and Kobe).  Not much is known about the butterfly, nobody is even sure what it’s caterpillars eat (it lays its eggs on dead leaves and the caterpillars then go in search of the host plant themselves).  Another baffling thing about Ypthima multistriata is the fact that it’s reproductive schedule seems to vary a lot even in populations living close together.  Some populations breed twice during the summer, while others breed only once.  Suzuki-san and his colleagues studied nine populations of the butterfly, thinking that the closely related populations would have the same reproductive pattern.  They found instead that the reproductive schedule wasn’t related to the genetic background of the population, but that each population had adapted independently to it’s location.  They now think that competition with other butterflies and different host plant quality are what determine the reproductive schedule of the butterfly.  This is a very interesting finding because it means that two populations living close together can evolve very different traits.  However,  there is still a lot more to be learned about this  rare species!

After checking up on the butterfly, we went on to Nara which was once the capital of Japan, and has a number of really beautiful historical sites, including a giant Buddha.  Legend has it that the god Takemikazuchi, rode in on a white deer to protect the city, so deer are considered sacred animals here.  Nobody is allowed to hurt them (although you can feed them special deer cookies sold at the temples), and they roam freely through the streets.   The following slide show is from our trip to the field site, and from the visit to Nara.

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