On the Importance of Contrasts in Taxonomic Diagnoses: A Survey of 405 Newly Described Insect Genera

Diagnoses are one of the most important ways that taxonomists make new taxa recognisable by others. A recent paper stated that diagnoses for newly described organisms should include both the characteristic(s) of the new taxon (providing state-specificity) and name the taxa with which they are compared (giving contrastiveness). I argue that the characteristics of the compared taxa should also be included such that the diagnostic features are not only contrastIVE but also overtly contrastED I surveyed 278 papers wherein 405 new insect genera were described. Forty-four genera did not have a formal diagnosis, among the rest, there was a total of 427 diagnoses because some genera had multiple diagnoses. Among these, 83 (19.4%) had one or more diagnostic states overtly contrasted and over one-eighth (13.9%) contrasted all of them. Unsurprisingly, diagnoses that overtly compared the new genus to others were significantly more likely to include characteristics that were contrasted than did diagnoses that were lists or combinations. I discuss how features should be contrasted in diagnoses.