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The Origins of the term "WATER SPIDER "

...from conversations with Chihiro Nakao


Amenbo means

The insect known in English as the "water strider" was Mr. Ohno's model for material delivery.

Whiligigs go round in circles, and diving beelts dive. Neither are good.

Not the whirligig or the diving beetle.


The water spider's hair should be flowing behind in speed.

However they got their name, WATER SPIDERS should scoot! Mr. Nakao's image looks something like this.

Translation is never exact. A good example of this is the English kaizen term "water spider" for the person who delivers materials to the line and picks up its completed products. Chihiro Nakao insists that I use this term for its Japanese equivalent: MIZU SUMASHI. But looking in the dictionary one finds different English words for MIZU SUMASHI, so I made a point of finding out its background. What I found was something of a linguistic mess. Those of you who like to nit-pick over meanings, and those of you who REALLY want to know, please read on. Others may find this bit of Kaizen Lore more complicated than interesting.

To begin with, the insect known as a "water spider" is not kaizen's model for material delivery at all -- it is rather the insect known as a "water STRIDER." And it gets even more complicated. The Japanese kaizen word MIZU SUMASHI, actually means "whirligig." So... the Japanese use the word MIZU SUMASHI which means whirligig, but they really mean "water STRIDER," and this was translated into English as "water SPIDER." Where did the confusion start? To find out we have to go back to when Taiichi Ohno coined the term.

Mr. Ohno's image for material delivery was the water strider because it scoots around quickly and takes care of its business very smoothly. When he watched a production line, he wanted to see the MIZU SUMASHI busily delivering materials just in time, taking many trips, and delivering limited quantities. Most Japanese were familiar with the water strider's miraculously smooth movements on the water of rice paddies, so the image should have been well understood.

But Mr. Nakao remembers that once someone took MIZU SUMASHI to mean "whirligig." Mr. Ohno corrected him saying: "NO! All that bug does is go round in circles! That's what I'm trying to get you to STOP doing! And some of you are even worse, you're like the diving beetle (GENGORO)! My MIZU SUMASHI is the water strider (AMENBO)!!

After that scolding few were willing to point out to Mr. Ohno that the dictionary meaning of MIZU SUMASHI was actually "whirligig," not "water strider." Mr. Ohno had made his point. Line-side material delivery should look like the effortless scooting back and forth of water striders -- no running in circles, no diving.

In later years Mr. Ohno was invited to speak about Just in Time to a Chinese audience. He struggled to find a word for MIZU SUMASHI in Chinese and someone suggested the Chinese water insect written with the characters for "water" and "spider." Mr. Ohno thought the term would do fine and used it for his first explanation of the MIZU SUMASHI to non-Japanese. So when Mr. Nakao and others began to teach Just in Time in the US and other countries, the "water spider" translation was the term that came to mind, and it's English version was used. Hence the birth of the term "water spider."

In conversations with kaizen consultants such as Mr. Nakao, some interpreters have realized from time to time that the dictionary translation of what Mr. Ohno meant by MIZU SUMASHI is actually "water strider" in English. Boeing is one company that uses "water strider" instead of "water spider," and this translation is highly justifiable.

But considering the fact that "water spider" was approved by Mr. Ohno, I prefer to use it as the translation of MIZU SUMASHI. Water flows, and spiders scoot. So the two images seem to be appropriate to kaizen lingo, and many English speakers now recognize "water spider," and understand what the term means. Mr. Nakao balks at the term "material handler" because the idea is to NOT HANDLE material. "Material handler" leaves an image of allowing activity for the sake of transporting and dealing with materials. The idea is to scoot materials to where they are needed in a flash -- not spend time "handling" them.


  • Here are the formal translations found in the GENIUS Japanese/English Dictionary of all the water insects that are dealt with in the above:
    • MIZUSUMASHI: whirligig
    • AMENBO: water strider ("water skeeter" if you're from Western NY State like I am)
    • GENGORO: diving beetle
  • MIZU SUMASHI appears to be a word that has meant different things to different people. Literally translated it means "water clearer." Perhaps because water insects seem to avoid stagnant water. Japanese poetry is filled with examples of MIZU SUMASHI obviously referring to water striders. One spelling of MIZU SUMASHI uses the kanji for "water" and "horse" -- an unlikely image for the whirligig.
  • KAWA GUMO, or "river spider" is another set of kanji that is meant to represent the water strider. Perhaps Mr. Ohno had this in mind when he approved of the original Chinese "water spider" term.
  • AMENBO always seemed to me to refer to AME as in "rain," but it apparently refers to AME as in "candy." Japanese claim that the water strider smells like sweet malt syrup. ... I defy anyone to smell a water strider and find out!
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