S. Mahunka szerk.: Folia Entomologica Hungarica 58. (Budapest, 1997)
Among the 56 European species having 7-segmented antennae, discal setae are present on sternites in females of 20 species, on pleurotergites in those of eight species, and on both of these sclerites in only five species. It appears conspicuously that the portion of species having discal setae on both sternites and pleurotergites is much bigger in the species having 8-segmented antennae (ten out of 14 species = 71.4%) than in those with 7-segmented antennae (five out of 56 species = 8.9%). In a discussion of how to classify the species of Thrips, the arrangement of the areae porosae on sternites in males should also be considered. The males of a distinct majority of the European species (72.3%) have an area each on five sternites, that is on III —VII. There is, however, a single species, conferticornis Priesner (1922: 93), with the most striking number of six sternites (III — VIII) each with an area, so far not known in any other species of the World fauna of this genus. Table 4 shows the distribution of the areae on sternites. Table 4. Distribution of areae porosae on sternites in males of 65 European Thrips species (males of six species are not known yet) Areae porosae on Number of species with Number of species with Total number of sternites 8-segmented antennae 7-segmented antennae species (%) III—VIII 0 1 1 (1.5) III—VII 12 35 47 (72.3) III—VI 2 6 8 (12.3) III-V 1 5 6 (9.2) III-IV 0 3 3 (4.6) The question as to the phylogenetical relevance of the number of areae porosae should be repeated here, in particular with regard to the valuation of that character, or to the direction of the morphocline. Schliephake (1975: 7) contemplates the presence of the areae in males as an apomorphic character, their absence as a plesiomorphic one. Aeolothripidae and Merothripidae lack areae porosae completely, hence both families are regarded as being phylogenetically old. In the remaining families the areae, and together with them the internal glands, are at least partly present, a character which seems to occur only in the more advanced families. Following up the same train of thoughts, the lack of areae in a number of taxa on both generic and specific level in the advanced families Thripidae and Phlaeothripidae has to be explained as a later resulted reversion. However, are there convincing counter arguments when the other way round is being postulated, that is the opposite direction of the morphocline? This would mean that the areae are of a plesiomorphic type of a character which in the course of the evolution has become subject to reduction in separate steps. According to this version, the glands and their areae porosae were developed as some sort of a latent character as early as in the proto-thysanopterans. Of course, there is so far no evidence for this hypothesis. If taken it for granted, this particular character underwent involution at a later phylogenetical stage as is manifested in the branches of Aeolothripidae and Merothripidae. In these two families the areae have either gone lost whatever the "reason" might have been; or their genetic instructions are not expressed phenotypically. Contrary to this, in the more advanced branches with the heterothripids in the old sense and those with the Thripidae and Phlaeothripidae, the areae maintained phenotypically in many taxa. But in some of the taxa a reduction of the areae had taken place although the inherited genetic instruc-
