Nomina dubia in the genusTheridionresulting from errors in instalment six of Carl Wilhelm Hahn’s “Monographie der Spinnen” (Araneae: Theridiidae)

An overlooked error in the correlation of new scientific names with the spider images on plate 4 in Carl Wilhelm Hahn’s sixth instalment of his book ”Monographie der Spinnen” led to the notion that at least two of the spiders illustrated on plate 4 cannot be identified and their names are nomina dubia. Here, I draw attention to the fact that, if the names are re-aligned to the images in a meaningful way, then at least three spiders on plate 4 can be identified. Theridion rufipes sensu Hahn is a synonym of Gongylidium rufipes (Linnaeus, 1758) (syn. conf.). In particular, the previous nomen dubium Theridion tibiale Hahn, 1831 is a senior synonym of Lasaeola tristis (Hahn, 1833) (syn. nov.). Evidence is presented that the junior synonym is in prevailing usage and the senior synonym is therefore regarded as nomen oblitum