Meaning
虫 means insect, bug, or worm — and covers any small crawling creature in everyday Japanese. In modern Japanese it encompasses everything from beetles and ants to worms and caterpillars.
Two common idioms show its figurative side. 虫の知らせ (a bug's notification) means a premonition or bad feeling. 虫が良い (the bug is good) describes someone acting selfishly or asking too much.
Etymologically, 虫 is a pictograph. In its ancient oracle-bone script form, it depicted a coiled snake or serpent, representing all manner of crawling creatures. The form simplified over time into the six-stroke character used today. In classical Chinese, the full character for insects was 蟲 — three 虫 stacked together, suggesting countless creatures. That traditional form survives in some formal Chinese contexts, while both languages now use the single simplified 虫.
Grade 1 in Japan's school curriculum, 虫 is one of the first kanji children learn. It acts as its own radical (部首), appearing on the left side of many creature-related kanji. Despite its simple shape, it shows up in a wide range of compounds and idioms throughout daily life.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi is チュウ, inherited from ancient Chinese pronunciation. It almost never appears alone — you encounter it in scientific and formal compound words (熟語 jukugo).
- 昆虫 (konchuu) — insect (the formal biological term)
- 害虫 (gaichuu) — pest (literally "damage-bug")
- 益虫 (ekichuu) — beneficial insect (e.g., ladybugs, bees)
- 幼虫 (youchuu) — larva, grub
- 成虫 (seichuu) — adult insect
- 寄生虫 (kiseichuu) — parasite (literally "parasitic creature")
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi is むし — the native Japanese word for bug. It's what you say in everyday conversation. Use it alone, or as part of compound words. It has a warm, familiar feel: the kind of word a child uses pointing at a caterpillar in the garden.
- 虫 (mushi) — bug, insect (the everyday standalone word)
- 虫歯 (mushiba) — cavity, tooth decay (literally "bug-tooth"; the idea that decay eats the tooth like an insect)
- 毛虫 (kemushi) — caterpillar (literally "hair-bug")
- 虫眼鏡 (mushimegane) — magnifying glass (literally "bug-glasses"; used to look closely at insects)
- 虫取り (mushitori) — insect catching (a beloved summer activity for Japanese children)
- 虫かご (mushikago) — insect cage
Common Words & Compounds
虫 appears in compounds across science, medicine, and daily life. Key examples, grouped by theme:
Nature & Science
- 昆虫 (konchuu) — insect (formal biological category)
- 幼虫 (youchuu) — larva
- 成虫 (seichuu) — adult insect
- 益虫 (ekichuu) — beneficial insect
- 害虫 (gaichuu) — pest
- 毛虫 (kemushi) — caterpillar
Health & Body
- 虫歯 (mushiba) — dental cavity
- 回虫 (kaichuu) — roundworm, ascaris
- 寄生虫 (kiseichuu) — parasite
Everyday Objects & Activities
- 虫眼鏡 (mushimegane) — magnifying glass
- 虫取り (mushitori) — insect catching
- 虫かご (mushikago) — insect cage
- 虫よけ (mushiyoke) — insect repellent
Idioms & Figurative Use
- 虫の知らせ (mushi no shirase) — premonition, bad feeling
- 虫が良い (mushi ga ii) — self-serving, asking too much
- 虫の息 (mushi no iki) — barely alive, breathing faintly
Example Sentences
庭に虫がたくさんいます。
Niwa ni mushi ga takusan imasu.
There are many bugs in the garden.
子供たちは夏に虫取りをするのが好きです。
Kodomotachi wa natsu ni mushitori wo suru no ga suki desu.
Children love catching insects in the summer.
虫歯が痛くて、歯医者に行きました。
Mushiba ga itakute, haisha ni ikimashita.
My cavity hurt, so I went to the dentist.
この虫眼鏡で虫をよく見ることができます。
Kono mushimegane de mushi wo yoku miru koto ga dekimasu.
You can see bugs clearly with this magnifying glass.
昆虫は地球上で最も多い生物です。
Konchuu wa chikyuujou de mottomo ooi seibutsu desu.
Insects are the most numerous living creatures on Earth.
害虫から野菜を守るために虫よけを使っています。
Gaichuu kara yasai wo mamoru tame ni mushiyoke wo tsukatte imasu.
We use insect repellent to protect the vegetables from pests.
出発する前に虫の知らせがして、傘を持っていきました。
Shuppatsu suru mae ni mushi no shirase ga shite, kasa wo motte ikimashita.
I had a premonition before leaving, so I brought an umbrella.
毛虫はやがて美しい蝶になります。
Kemushi wa yagate utsukushii chou ni narimasu.
Caterpillars eventually become beautiful butterflies.
彼女のお願いは虫が良すぎると思います。
Kanojo no onegai wa mushi ga yosugiru to omoimasu.
I think her request is asking a bit too much.
Memory Tip
Look at the shape of 虫. The top resembles a head, and the bottom encloses a small space — like a creature curled inside a shell. Picture a bug hiding in a tiny cage. The six strokes mirror the six legs of most insects: six strokes = six legs = insect. In its ancient oracle-bone form, 虫 depicted a coiled serpent — a worm curled in on itself. That image still fits. Every time you see 虫, think: something small, crawling, and alive.