Insects are an extremely diverse class of mainly terrestrial arthropods (arthropods are invertebrates in the ecdysozoa, with an exoskeleton made of chitin), with a million named species and more to be discovered. At least 1.2 trillion individual insects are farmed each year for food and feed around the globe, with trillions (perhaps quadrillions) affected by human activity in other contexts. The question of insect pain is an open one, i.e. without broad scientific or philosophical consensus. This chapter examines the history of scientific interest in the subject and presents the neurobiological and behavioural evidence related to insect pain. The potential pain and suffering experienced by farmed insects during rearing, transport and slaughter are reviewed while acknowledging the uncertainty of insect pain perception and the lack of validated tools for assessing it. The chapter also reviews analgesics and anaesthetics for use in insects and examines the attitudes of consumers, producers, academics and others to insect pain. The diversity, and contexts of use, of arthropods other than insects and crustaceans are briefly reviewed before concluding with the complexity of moral caution in the insect case.