Eurasian blue tit host is "Proctophyllodes stylifer". However, this mite seems to be of no concern to the bird as, until now, it is only known to feed on dead feather tissue. "P. stylifer" lives all its developmental stages, i.e. egg, larva, protonymph, tritonymph and adult, within the plumage of the same host. The usual sites where "P. stylifer" is encountered are the remiges and the rectrices of the bird where they can be found tandemly positioned between the barbs of the rachis. The Eurasian blue tit is classified as a least concern species on the IUCN Red List (version 3.1), and as
Acorus calamus asexually. The tetraploid variety is usually known as "Acorus calamus var. angustatus" Besser. A number of synonyms are known, but a number are contested as to which variety they belong. It is morphologically diverse, with some forms having very broad and some narrow leaves. It is furthermore also cytotypically diverse, with an array of different karyotypes. "A. calamus" has been an item of trade in many cultures for thousands of years. It has been used medicinally for a wide variety of ailments, and its aroma makes calamus essential oil valued in the perfume industry. The essence from the rhizome is