About the rarity of the work - today, only about 14 – partially incomplete – copies are known. They were recorded and examined by Sacher from Germany (Wittenberg, Berlin, Jena, Darmstadt, Erlangen, Kiel, Munich, Frankfurt/M.), England (London), U.S.A. (Cambridge/Mass.), Austria (Vienna), and France (Paris). ""Monographie der Spinnen"" has become a rarity already at the beginning of the 20th century. This rarity is because only small editions were produced: "More than a hundred copies of each installment will not be produced.", remarked Hahn on this subject in 1820. The great rarity of complete copies probably results primarily from the long gap between installments. Ascertaining whether Hahn broke with his publisher or Lechner with him has not been possible, but a separation took place some time before the publication of the sixth installment. Indeed, in 1831, the first installment of ""Die Arachniden"" had already appeared in Zeh's Bookshop in Nuremberg as an obvious substitute for the ""Monographie der Spinnen"". It was more accessible, thus also better known than the ""Monographie der Spinnen"". In the sixth installment of the ""Monographie der Spinnen"", publisher Lechner 1831 inserted a small-format "message", which announced that Hahn had been relieved as editor. Probably the contents of the sixth installment still can be wholly attributed to Hahn, though he had only admitted to the first five installments. For obvious reasons, Lechner was not in a position to print anything new, though he still had original drawings in his possession, which he published without Hahn's consent. For this reason alone, competing with Hahn's new project was already impossible. So not surprisingly, the promised ninth installment failed to appear.