Insect Day (Mushi no Hi)

What is Insect Day?

Every year on June 4th is "Insect Day" (Mushi no Hi). The date comes from a number-sound pun: "mu" (6) + "shi" (4) = "mushi," meaning "insect." It was established in 1988 by the Japan Insect Club, at the call of the famous manga artist Osamu Tezuka and others; Tezuka, a well-known insect lover, served as the club's first president. The anatomist Takeshi Yōrō has also designated June 4th as Insect Day and holds a memorial service for insects at the "Mushizuka" (insect mound) at Kenchō-ji Temple in Kamakura, Kanagawa. The day is an occasion to think about the relationship between people and insects and to look at the nature around us.

Insects and Humanity

Insects are the most species-rich group of living things on Earth and have been deeply intertwined with human history.

• More than half of named species: Of the roughly 1.75 million species that have been named, insects account for about 1 million. Insects are thought to have appeared on Earth around 400 million years ago.
• The Silk Road and silkworm farming: Silk, made from silkworm cocoons, traveled west from ancient China along the Silk Road and supported trade between East and West. In Japan, raw silk became a leading export in the Meiji era.

The "Mushizuka" at Kenchō-ji

In 2015, at the suggestion of Takeshi Yōrō, a memorial for insects called the "Mushizuka" was built at Kenchō-ji in Kamakura. It was designed by architect Kengo Kuma. It serves as a place to honor the insects that have died in the course of human life, and a memorial service is held there every June 4th.

Fascinating Facts About Insects

• The broad meaning of "mushi": In Japan, "mushi" has long referred not only to insects but also to spiders, centipedes, and even snakes (the character for "mamushi," a viper, contains the insect radical). Expressions like "hara no mushi" (the "bug" in one's belly) and "mushi no shirase" (a premonition) also describe something inside us that affects our mood or health.
• Flea jumping power: Fleas are said to jump about 100 times their body length. One secret is resilin, a rubber-like elastic protein that stores energy like a spring and releases it all at once.
• The honeybee dance: Honeybees perform a "waggle dance" inside the hive to tell nestmates the direction and distance of flowers. Karl von Frisch shared the 1973 Nobel Prize in Physiology or Medicine for this research.
• Technology inspired by moth eyes: The surface of a moth's eye has fine bumps that suppress light reflection, and anti-reflective films imitating this "moth-eye structure" have been put into practical use.
• The origin of hook-and-loop fasteners: Hook-and-loop fasteners such as Velcro were invented by a Swiss engineer inspired by burrs (from a burdock relative) that stuck to clothing.
• Interest in edible insects: In 2013, the UN Food and Agriculture Organization (FAO) published a report on edible insects, drawing attention to them as a possible future food source. In Japan, foods such as locusts simmered in soy sauce (inago no tsukudani) and bee larvae (hachinoko) have long been eaten.

Tips for Spending Insect Day

• Look for insects in a nearby park or garden and observe them closely.
• Look into everyday products inspired by living things, like hook-and-loop fasteners.
• Pick up a book by an insect-loving author or scientist, such as Osamu Tezuka's works or Takeshi Yōrō's books.
• Grow flowers on your balcony or in your garden that attract butterflies and bees.

A Day to Look at the Small World at Your Feet

June 4th is a day to turn our attention to the "tiny neighbors" we often overlook. Just as Osamu Tezuka loved insects so much that he put the character for "insect" (虫) in his pen name, the world of insects holds a fascination that can captivate adults too. Today, why not pause for a moment and observe the insects around you?