Mihi itch or Mihisucht is the ambition to describe new species (or other taxa: subspecies, hybrids, genera, etc.)
Mihi is the dative form of the Latin word ego, thus "mihi itch" means to satisfy one's egotistical impulses.
[1] The expression appeared in print as early as 1884.
[2] A consequence of the Mihi itch may be the unwarranted description of new taxa, differing only slightly from already established taxa, leading to taxonomic inflation.
A more extreme case may be termed taxonomic vandalism when a large number of species are described with limited scientific evidence.