of butterflies across varying seasons and regions. In general, there is movement towards wetlands to reproduce. After the eggs hatch, develop, and pupate, newly hatched adult butterflies emerge and disperse locally into both woodlands and wetlands to overwinter. Butterflies travel to the woodlands for overwintering, and no mating appears to occur within these habitats. Overwintering also occurs in the wetlands, where the host plant alder buckthorn is abundant. After emerging from overwintering, adult brimstones that were previously in the wetlands are joined by those that hibernated in woodlands, and the population breeds and lays eggs. The environmental conditions of a particular year also affect migration, as seen in the elevational migrations of the common brimstone. Uphill migration is potentially influenced by habitat limitations, such as a lack of the forest cover that is required during overwintering. Brimstones travel to higher elevations for greater forest cover and reduced exposure to higher temperatures during their activities. Downhill migration is influenced by the need for larval resources such as host plants during breeding seasons - the butterflies travel to lower elevations in search for regions containing these plants, with adults commonly returning to the areas where they had been bred due to their long lifespan. Enemies Predators Like most woodland Lepidoptera, G. rhamni is preyed upon by many species of birds and wasps. Both larvae and adult brimstones fall victim to predation and use means such as protective coloration and mimicry to avoid this fate. Parasites The common brimstone has two recorded species of parasites: the braconids Cotesia gonopterygis and Cotesia risilis. These two species of parasitoid wasps are completely specialised for G. rhamni, possibly due to the wide distribution of the butterfly and the host plants in its habitats. The broad presence of its host allows the wasps to be host-specific. The wasps are primarily associated with the presence of the food plant Frangula alnus due to its association with their host. Protective colouration and behaviour Both the larval and adult common brimstone exhibit cryptic colouration, meaning they match the colour of their habitats. Larvae are so difficult to see due to this colouration that they can remain in the open undetected. When not eating, the caterpillars remain still in a position alongside the midrib of leaves, making them even more difficult to spot. Adult brimstones are leaf-mimics, as they share similarities in shape, colour, and pattern to leaves. This allows them