POLYMORPHISM AND KLEPTOPARASITISM IN THRIPS (THYSANOPTERA, PHLAEOTHRIPIDAE) FROM WOODY GALLS ON CASUARINA TREES

Two species of Iotatubothrips are now known, both inducing woody stem galls on Casuarina trees In Australia, and the single known species in each of Phallothrips and Thaumatothrips kleptoparasitise these galls. All four species of thrips vary remarkably in body form, in associati on with wing and behavioural polymorphisms, In particular, the previou sly unknown macropterae of Phallothrips houstoni are strikingly differ ent in body form from the apterae of this species. The weakly armed ma cropterae invade Iotatubothrips galls, isolate themselves individually within a small, self-built enclosure, and produce a brood of highly a rmed apterae that then leaves the enclosure and usurps the gall. In co ntrast, macropterae of Thaumatothrips froggatti are well armed and hea vily sclerotised, and apparently do not isolate themselves within a ga ll subsequent to invading it. One of the two species of Iotatubothrips is here newly described as Iotatubothrips kranzae. It is remarkable b ecause the male genitalia are about 55% longer in macropterae than mic ropterae, and are longer than in any other thysanopteran. This is the first recorded instance of genitalic dimorphism within a Thysanoptera species. This species is from Western Australia on Casuarina obesa, wh ereas the previously known species, Iotatubothrips crozieri, is from e astern Australia on Casuarina cristata and Casuarina pauper. In contra st, no significant morphological differences were detected between the eastern and western populations of the Phallothrips and Thaumatothrip s species on these tree species. All four thrips species exhibit unusu ally high intrapopulation variation within all morphs, and this may be related to fluctuations in within-gall density and, for the kleptopar asites, deterioration of feeding conditions in older galls.