The Japanese word for "Bug" is mushi 虫.
- Broad mushi 虫In the past, it was thought that animals were divided into "furries," kemono 獣, fishes, birds, and literally everything else was mushi 虫. Hence why the term is so broad, even today. You can tell an animal was considered to be a mushi because its kanji will have the 虫 radical. For example, "Frogs," kaeru 蛙, and "Snakes", hebi 蛇, don't have fur, so they were considered to be mushi.
The word "Bug" katakanized would be bagu バグ.
Beware: some kanji that are difficult to handwrite are easy to type on the computer, which may skew the usage statistics.