Moths are a diverse group of insects, with over 160,000 known species globally, far outnumbering butterflies. They exhibit diverse colors, patterns, and behaviors, and can be found in various habitats from forests to urban gardens. While many people associate moths with nighttime activity, their active periods vary significantly across different species.
Daily Activity Rhythms
Moth activity patterns are categorized into three main rhythms: nocturnal, diurnal, and crepuscular. Most moth species are nocturnal, active during the night and often attracted to artificial light sources. Examples include many hawk moths, like the tobacco hawk moth, which feed on night-blooming flowers. These moths are significant pollinators.
Some moth species are diurnal, flying during the day and often mistaken for butterflies due to their colorful wings. The hummingbird hawk-moth (Macroglossum stellatarum) is a well-known diurnal species that hovers near flowers to feed on nectar, much like a hummingbird. Other examples include the Bella Moth, Cinnabar Moth, and Lunar Hornet Moth. These day-flying moths have evolved adaptations like bright coloration, which aids in pollination and deters predators.
A third category is crepuscular moths, active during the twilight hours of dawn and dusk. Many hawk moths fall into this group, visiting flowers as the sun sets or rises. The white-lined sphinx (Hyles lineata) is one such crepuscular species, feeding on flowers from dusk until dawn. This varied timing allows different moth species to access specific food sources and avoid certain predators.
Seasonal Presence
Moth activity also follows distinct seasonal patterns, influenced by their life cycles and regional climates. Many species emerge and are most active during late spring and summer, when temperatures are warmer and food sources are abundant. Their life stages—egg, larva (caterpillar), pupa, and adult—often align with the seasons. A common overwintering strategy is to remain in the pupal stage, often in leaf litter or soil, emerging as adults in the spring.
Some moth species, like the Winter Moth, are adapted to be active as adults during colder periods, even flying on warmer winter nights. These moths can shiver their flight muscles to generate heat and have “furry” abdomens for insulation. Other species overwinter as eggs, larvae, or adults, finding sheltered spots like tree bark or buildings. Multi-brooded species can have several generations within a single year, leading to multiple peaks of activity from spring through autumn.
Environmental Influences on Activity
External environmental factors significantly influence when moths are active, affecting both their daily and seasonal rhythms. Light levels are a primary driver; while many nocturnal moths are attracted to artificial lights, excessive light pollution can disrupt their navigation and natural behaviors. Moonlight can also influence activity, with some moths reducing flight during full moons to avoid predators.
Temperature is another important factor, as moths are ectothermic, meaning their body temperature is influenced by their surroundings. Most moths have an optimal temperature range for flight, often between 25-27.5°C, with activity decreasing significantly below certain thresholds. To enable flight in cooler temperatures, moths can shiver their flight muscles to raise their body temperature.
Humidity also affects moth behavior, impacting survival and foraging. Some hawk moths adjust foraging based on ambient humidity, increasing nectar intake in low humidity. High humidity can also be favorable for egg laying and larval development in certain species. The availability of food sources, such as nectar from blooming flowers, further dictates moth activity, as moths are often found where their preferred plants are abundant. These combined environmental conditions can trigger or suppress moth activity regardless of their inherent daily and seasonal patterns.