Insects and Climate: Seasonality, Migration, and Diapause

Insects synchronize their life cycles with seasonal changes in temperature, day length, and food availability. Some species migrate thousands of miles to track favorable conditions, while others enter diapause—a programmed dormancy—to survive harsh winters or dry seasons. Understanding these strategies helps predict how insects will respond to climate change across North America.

Seasonal Timing and Phenology

Many insects emerge at precise times each year, triggered by accumulated degree-days or photoperiod cues. Eastern tent caterpillars hatch in early spring when host trees leaf out, while periodical cicadas emerge in 13- or 17-year cycles synchronized across vast regions. Climate warming is shifting these timing patterns: some species emerge earlier, creating mismatches with their food plants or predators.

Tracking first emergence dates—when you first see a particular butterfly, dragonfly, or beetle each year—helps scientists document phenological shifts and understand ecosystem-level consequences.

Migration: Long-Distance Travelers

Monarch butterflies undertake one of the most spectacular insect migrations, traveling from breeding grounds across the United States and Canada to overwintering sites in Mexico and coastal California. Dragonflies like the green darner also migrate, riding favorable winds southward in fall. These migrations require precise navigation using sun compasses, magnetic fields, and landscape features.

Climate change threatens migrations by altering wind patterns, reducing overwintering habitat, and disrupting the timing of nectar availability along migration routes.

Diapause: Surviving the Off-Season

Diapause is a state of suspended development that allows insects to survive unfavorable conditions. Many temperate species enter diapause as eggs, larvae, or pupae, resuming development when temperatures warm or day length increases. Some desert insects enter diapause during dry periods, emerging only after rainfall triggers plant growth.

Warmer winters can disrupt diapause timing, causing insects to break dormancy too early and face late freezes or lack of food resources.

Insects' responses to climate—through migration, diapause, and phenological shifts—reveal both their remarkable adaptability and their vulnerability to rapid environmental change. Your observations contribute to understanding these dynamics and informing conservation strategies.