univoltinism

Univoltinism is a life-history strategy in which a species completes one generation per year. In insects, univoltine populations typically carry out the entire life cycle—from egg to larva or nymph to pupa to adult—within a single annual cycle and survive unfavorable seasons in a diapause or resting stage. The pattern is closely tied to seasonal resource availability and environmental conditions that favor development at a single, decisive time of year.

The number of generations per year is influenced by environmental cues such as photoperiod and temperature, and can be obligate (fixed) or facultative (flexible) depending on the species and population. In temperate regions, univoltinism often evolves as an adaptation to short growing seasons and a harsh winter, with diapause typically occurring at a specific life stage to bridge unfavorable periods.

Ecologically, univoltine species synchronize their life cycles with the phenology of resources, such as host plants, and with climate patterns. They may be particularly vulnerable to climate change, which can shift the timing of resource peaks and disrupt the match between life stages and available resources. Compared with bivoltine or multivoltine species, univoltine taxa generally have fewer generations per year, which can constrain population growth but may stabilize populations when seasonal resources are predictable.

Univoltinism occurs across several insect groups, most prominently among Lepidoptera (butterflies and moths), and is also observed in some Coleoptera and Diptera in temperate zones.