Ecology and evolution of galling thrips and their allies.

About 300 species of thrips belonging to 57 genera are known to form galls. Galls are caused by feeding, usually by one or more adults, on actively growing plant tissue. Most thrips genera with galling capabilities exploit multiple plant families, but there are several possible cases of thrips tracking the speciations of their host-plants. Gall morphology in thrips reflects insect phylogenetic relationships rather than those of plants. Galling species and their nongalling allies on Acacia in Australia exhibit a range of complex social behavior, including soldier castes, pleometrosis (i.e. joint colony founding), group foraging, and group defense, that is directly related to the nature of their domiciles. Galling thrips, by virtue of their haplodiploid genetic system and their ecological relationships with plants and natural enemies, are useful for analyzing a wide range of ecological, evolutionary, and behavioral questions.