Recent models have identified evolutionary explanations for sensitive periods, when individuals are more responsive to experiences at certain stages of development, based on benefits and costs of attending to environmental cues. Empirical tests of these models face challenges, requiring complex, long-term experiments, and detailed understanding of physiology and ecology. Insect systems offer the opportunity to overcome these challenges, given their tractability, diversity and well-studied mechanisms. These studies shed light not only on fundamental biology, but have societal implications given the roles insects play in pollinating or decimating food crops and in spreading parasites. Understanding the role of sensitive periods can help to protect beneficial insect populations while controlling pests and vectors of disease.