The significance of morphological variation within the Thrips hawaiiensis (Morgan) species-group is examined. Multivariate analyses of four characters from 344 females and seven characters from 90 males show two distinct groups found throughout the Oriental, Pacific and American Regions, corresponding to T. hawaiiensis and T. florum Schmutz, and an intermediate group, exilicornis Hood, from Africa. The results are compared with previously published morphometric data concerning the separation of T. hawaiiensis and T. florum, and additional distinguishing characteristics are assessed. The distributions of the three forms as recognized in this study are summarized.

Multivariate analysis was used to demonstrate that specimens of Pianococcus collected from yams (Dioscorea spp.) in both the West Indies and Africa can be differentiated from the similar P. ficus (Signoret) which occurs on figs, grapevines and pomegranates in the Mediterranean Basin, Pakistan, South Africa and Argentina. The specimens from yams are considered here to be a distinct species, to which the name P. halli Ezzat & McConnell is applied. Examination of material of both species reared on potato tubers at various temperatures showed that the differentiation is not a host-induced effect. Independent canonical variates analysis of the field-collected and reared material each showed clear differentiation of the two groups. However, the coefficients obtained for each character differed markedly between the analysis of the field-collected material and that of the reared material, and thus could not be used to assign individuals to groups. This difference in the values of the coefficients is considered to have been due to the peculiarities of individual populations, as the field-collected material included many genotypes while only three genotypes were represented by the reared material. A key and illustrations are provided for the separation of the two species.

. Morphological variation among freshly caught specimens resembling Folsomia quadrioculata Tullberg was examined using principal components analysis and canonical variates analysis. Two distinct groups were identified corresponding with F. quadrioculata and F.manolachei Bagnall. Previous workers have questioned the specific status of F.manolachei and regarded these two species as inseparable using morphometric characters. A study of specimens previously identified as F. quadrioculata suggested that many were mis‐identified and that F.manolachei is more abundant in the British Isles than is usually thought. Variation in some characters traditionally used to identify Folsomia species was examined and a method for distinguishing adult and juvenile F.quadrioculata from F.manolachei is provided. The synonomy of F.nana Gisin with F.manolachei is supported. The separation of F.diplothalma Axelson from F. quadrioculata is discussed, concluding that no characters are known which can reliably separate British specimens of these species.

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