A physiological state of arrested development, occurring in some insect and acarine species in precise developmental stages, or expressed in adults as reproductive immaturity. It may be induced, in anticipation of seasonal deterioration of habitat and/or adverse climatic conditions, by photoperiod, temperature, food and/or humidity. When occurring, it is usually facultative, although in some cases it may be obligatory. Displacement in time (diapause) may be regarded as an alternative to displacement in space (e.g. migration).