No Japanese person I’ve asked yet was aware of it (though none of them are kanji fanatics or Japanese language teachers). All of them knew the word ぼうふら, but some of them didn’t know ぼうふら are the larvae of mosquitos. They thought it was some other kind of animal altogether.
But it is now burned indelibly into all of our memories. Just think of how appreciative the small isolated, helpless mosquito larvae must feel knowing that we can understand stories written just about them!
When I search that word I also get 棒振 as another combination, and then right under it, I see the entry for 孑孑. I wonder if it’s usually writing with the former kanji. And by usually, I mean when it’s not usually written in kana alone.
棒を振るような泳ぎ is offered as an explanation of the origin of the word. So that’s where that kanji comes from. It’s almost never written in kanji in any sense. 孑孑 is probably the “correct” way if you wanted to write it in kanji and you were doing so in a serious (scientific?) setting.
I was reading about mosquitoes and the word ぼうふら appeared in hiragana, and I just looked it up (even though it was explained as 蚊の幼虫 within the sentence). I just was shocked at the kanji when the dictionary entry came up.
Oh, and the reason I was reading about mosquitoes is because I was studying the kanji 吻 (ふん proboscis) for Kanken level pre-1 and I just assumed that stuff about mosquitoes would use it. And I was right about that.
Fun fact about that kanji, the word 接吻 (せっぷん) is like… the technical term for kissing.
Since you’ve made my brain hurt after a rather lengthy review, I’ll leave you with the page I like to use as a test of how far I’ve come… It helps that I actually know a fair bit about this in English.
Yeah, I know the concept in English roughly, so even though I’ve never seen most of those words before, I didn’t have trouble following what I read of it. Long scientific kanji compounds are usually good about being pretty literal in their meanings, except when the concept gets tangled up with pre-scientific ideas I guess.