Common Brimstone

The Common Brimstone can be commonly found throughout the Palearctic. Individuals have been seen from western Europe to east Asia. The high mobility of this butterfly allows it to search widely for new host plant locations and expand its range. While the geographic distribution of the adult is larger than that of its host plant, its range is nevertheless limited by the presence of host plants due to the needs of its larval stage. The Common Brimstone uses various environments for different stages of its life cycle. The butterfly inhabits wetlands during mating and breeding season, as they provide ideal areas for oviposition due to an abundance of host plants like the alder buckthorn. The Common Brimstone prefers laying eggs on younger host plants with late bud-bursts that are isolated from other plants in the area and exposed to both open space and sun. During the winter, adult brimstones travel to woodlands to hibernate, as they provide ideal overwintering sites with shelters such as evergreen foliage and holly. The Common Brimstone has an appearance that is highly similar to the leaves of these plants, so during hibernation it can remain hidden. In other seasons, habitat selection is also affected by the abundance of nectar as a food source for adult brimstones.

The common brimstone is one of the longest-living butterflies, with a life expectancy ranging from 10 months to a year. Due to its hibernation and life cycle, it has one generation per year. Development from the laid egg to the emergence of the imago is approximately 50 days. However, the adult brimstone spends a large portion of its life in an overwintering state. The brimstone is highly mobile, feeding and travelling to regions ideal for hibernation during the late summer and fall, and returning to regions ideal for mating and egg-laying during the spring.

Egg. Adult Common Brimstones lay eggs singly on the underside of buckthorn leaves. The eggs are around 1.3 mm tall, and are spindle-shaped in appearance. The eggs change colour over time, initially having a greenish-white colouration, then progressively darker shades of yellow, and finally brown before hatching.

Caterpillar. The larvae of the common brimstone undergo five instars, initially having a length of 1.7 mm in the first instar and reaching up to 34.9 mm in length when fully grown. The caterpillars have a green colouration with white hairs and dark tubercules across its length. When they first hatch, they move to the top side of the leaves and eat them, leaving characteristic hole patterns in their host plants. …