Insects dominate virtually all terrestrial and freshwater habitats on earth. This chapter reviews insect habitat selection, focusing on the occupation and defence of mating sites. First the adaptive basis of mating systems, sex roles, and behaviors in regard to habitat are established, then site occupation and defence in territorial species is explored. Resource-holding potential and resource value are discussed for how they determine aggressive motivation, as well as how contestants seek to gauge such parameters, with particular attention to the role of convention, drawing upon exemplar studies in damselflies and butterflies that have provided a narrative between theory and empiricism. Conventional and/or plastic behaviors are also discussed in terms of the presence and certainty of contestant roles, encompassing phenomena, such as residency confusion, nasty neighbours and interloper effects. The chapter concludes by discussing future avenues, foremost among which is the opportunity to synthesize empirical data across taxa.