Why are the names of plants and animals often written in katakana?


I was wondering why fruits, vegetables, animals and plants, are written in
_katakana_? Often, there exist _kanjis_ for those, so why aren't they written
with those _kanjis_ instead? For example:

  * カマキリ instead of 蟷螂
  * ヒマワリ instead of 向日葵
  * シイタケ instead of 椎茸
  * バナナ instead of 甘蕉




This depends on the type of the words.

  * As for easy and common words, such as 桜, 犬, 蚊, they are usually written _in kanji_. These are written in katakana only in biological contexts. 常用漢字表 generally tells us what is considered easy and standard in modern Japanese. If you wrote "東京はサクラがきれいです" or "イヌを飼いたいと思う", that would look unnatural.

  * Relatively difficult words whose kanji are not listed in 常用漢字表, such as 薔薇, 豹, 蜻蛉, are usually written in katakana or hiragana in newspapers and official documents. People can generally read these kanji, but don't remember how to write them with confidence, because they are not something we learn at school. Using kanji for those words (with the aid of IME) is generally safe, but that may look too stiff or literary. Whether to use katakana or hiragana is up to the writer's taste. Katakana may look a bit technical, but it does stand out in the sentence, which will help us read smoothly.

  * There are hundreds of plants/animal names whose kanji are simply too difficult. I think majority of the Japanese population do not know (and do not want to know) how to read 紫萁, 臘虎 and 蟷螂. We have no choice but to use either hiragana or katakana in these cases.

  * Loanwords such as バナナ, チンパンジー, ピラニア must almost always be written in katakana. This is not surprising, is it? There may be 当て字 or corresponding Chinese names (香蕉, 黒猩々, ...) but they are only for kanji maniacs.




This depends on the type of the words.

  * As for easy and common words, such as 桜, 犬, 蚊, they are usually written _in kanji_. These are written in katakana only in biological contexts. 常用漢字表 generally tells us what is considered easy and standard in modern Japanese. If you wrote "東京はサクラがきれいです" or "イヌを飼いたいと思う", that would look unnatural.

  * Relatively difficult words whose kanji are not listed in 常用漢字表, such as 薔薇, 豹, 蜻蛉, are usually written in katakana or hiragana in newspapers and official documents. People can generally read these kanji, but don't remember how to write them with confidence, because they are not something we learn at school. Using kanji for those words (with the aid of IME) is generally safe, but that may look too stiff or literary. Whether to use katakana or hiragana is up to the writer's taste. Katakana may look a bit technical, but it does stand out in the sentence, which will help us read smoothly.

  * There are hundreds of plants/animal names whose kanji are simply too difficult. I think majority of the Japanese population do not know (and do not want to know) how to read 紫萁, 臘虎 and 蟷螂. We have no choice but to use either hiragana or katakana in these cases.

  * Loanwords such as バナナ, チンパンジー, ピラニア must almost always be written in katakana. This is not surprising, is it? There may be 当て字 or corresponding Chinese names (香蕉, 黒猩々, ...) but they are only for kanji maniacs.

