S. Mahunka szerk.: Folia Entomologica Hungarica 58. (Budapest, 1997)

ROVARTANI KÖZLEMÉNYEK LVIII 1997 pp. 227-235 How to classify the species of the genus Thrips (Thysanoptera)? R. zur Strassen How to classify the species of the genus Thrips (Thysanoptera)? - The genus Thrips Linnaeus is one of the largest genera in the order Thysanoptera comprising about 275 species. It is difficult to work out a useful key to species of this genus if certain phylogenetic groupings of the species are to be taken into consideration. In order to get an approximate phylogenetic line of the species, the question is discussed which of the ancestral (plesiomorphic) characters are "older" than other ones, and in contrast, which of the advanced (apomorphic) characters are "younger" than others. INTRODUCTION In the order Thysanoptera the genus Thrips Linnaeus (1758: 457) is one of the largest genera comprising about 275 extant species. This figure results from unpublished working catalogues of L. A. Mound and the writer. Palmer (1992: 1) quotes 250 species. More than further 110 species have turned out in the past to be synonyms. As to the morphology, Thrips is a rather uniform taxon with the females being more monotonous than males. Considering the big number of species, it is not surprising to taxonomists to recognize the difficulties in distinguishing these species from another. It is certainly more difficult to prepare a key to species based on reliable and fairly easily detectable characters. And finally, it is still more arduous to group the species by means of certain features which may possibly be of some phylogenetical valence. Palmer (1992: 60) was recently occupied with this problem and discussed it in detail. A good number of characters commonly used in present time was unknown to our respected forefathers in res Thysanopterorum. Uzel (1895: 53) and the early Priesner (1927: 343) have in their keys to the European Thrips species more often referred to colour pattern than is the practice today. Too many species exhibit each a wide range of colour pattern which in such cases become useless for separating species or species groups. In running down Uzel's key to 21 species, Thrips minutissimus Linnaeus (1758: 457), the common European leaf inhabitant of deciduous trees in spring, is reached after six steps, three (= 50%) of which are dealing with colour. In case of the abundant flower inhabitant, Thrips flavus Schrank (1776: 31), there are in the same key to species also six steps, but four (= 66%) of which are concerning with colour. Similarly, in the key to 42 species by Priesner, five steps are needed to come to minutissimus with three (= 60%) of which indicating colour pattern; accordingly, the figures for flavus are nine steps with five (= 55.5%) on colour.