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

During the second half of the present century an increasing number of detailed morphological characters have been tracked in Thysanoptera and afterwards introduced to keys to species reducing herewith the need of references to colour pattern. This development is partly reflected by the data given in Table 1. Table 1. Relation of the total number of couplets in keys to species of Thrips, and those with a statement on colour pattern used for females References Total number Number of Region treated Number of of couplets couplets with species coloration Priesner 19646: 84 93 44 (47.3%) Europe 62 Gentile and Bailey 1968: 16 30 15 (50.0%) North America 31 Mound et al. 1976: 46 34 16 (47.0%) British Islands 34 Bhatti 1980: 113 38 15 (39.5%) India 33 Palmer 1992: 9 93 38 (42.2%) Orient, Pacific 91 Nakahara 1994: 15 67 35 (52.2%) New World 61 RESULTS How to group the species? As far as the colour pattern is concerned, there are several Thrips species with a wide range of variation. The polyphagous cosmopolitan Thrips tabaci Lindeman (1888: 72) is in the genus one of the species occurring in all colour shadings from dark greyish brown to pale yellow, or even to almost whitish. Such a species cannot be placed in any group if these refer mainly to certain colour pattern. The unsatisfactory alternative in this case would be the placement of tabaci in every of these groups. Which other criteria except for colour pattern have to be recognized in Thrips for establishing species groups? As stated already, hardly any striking physical characters are existing in that genus with but one exception. In the Holarctis, 77?. calcaratus Uzel (1895: 195) is unique in having distinctly armed fore tarsi, that is a tooth at the inner apical edge of their terminal segment. There are in the genus only two further species being equipped also with a fore tarsal tooth, both from the Australian/New Zealand region. Less striking but by all means useful distinguishing characters are the different numbers of antennái segments (eight, or seven); the shape as well as the ratio length/width of some of these segments; the size of certain parts of the body; the type of line sculpture of and the presence, or absence, of campaniform sensilla on certain sclerites; the nature of microtrichia on the pleurotergites; the state of a comb of microtrichia on the hind margin of tergite VIII; and additionally, in males the number and size of areae porosae on the stern ites. The structural monotony of the species as well as their still increasing number has forced taxonomists to search more often than usual for characters from the field of chaetotaxis. This term means the designation (size, shape of tip, position) and taxonomical utilisation of hairy structures (bristles, setae). Certain setae inserting at defined positions of the body have in many species a strong systematic value. The same applies in other species, or species groups, to the absence of setae from the same defined positions.