müller was an early investigator of coevolution.p27 he was the author in 1873 of "die befruchtung der blumen durch insekten", a book translated at the suggestion of darwin in 1883 as "the fertilisation of flowers". he and darwin corresponded—36 letters between the two, or from darwin concerning müller, are recorded. darwin cited him extensively in "the descent of man" for his information about the behavior of bees.