Gonepteryx rhamni, commonly named the common brimstone, is a butterfly of the family Pieridae. It lives throughout the Palearctic zone and is commonly found across Europe, Asia, and North Africa.
Taxonomy
It was first described and published in Linnaeus's book, the 10th edition of Systema Naturae in 1758.
Brimstone is an old name for sulphur, the colour which matches the colour of the male's wings.
Distribution and habitat
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.
Food resources
left|thumb|The common buckthorn, one of the larval host plants.|220x220px
Caterpillar
Larval brimstones appear to feed on only two plant sources: the alder buckthorn (Frangula alnus) and the common buckthorn (Rhamnus cathartica). This influences the distribution of the adult brimstone, as the presence of these two buckthorn species is necessary for the survival of their offspring. The high mobility of G. rhamni enables the butterflies to find even the most isolated host plants in an area, which are more ideal for their offspring. The eggs change colour over time, initially having a greenish-white colouration, then progressively darker shades of yellow, and finally brown before hatching. The common brimstone hibernates for the next seven months of winter, remaining inactive until April, where they then emerge and proceed to reproduce and lay eggs. Both males and females have orange spots in the discoidal cell of each wing, pink head and antennae, and a thorax covered in white hair. 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. Due to these pigments, the beads absorb short wavelength light and scatter longer wavelengths outside of the pigment absorption spectrum, such as light in the complementary wavelength range. This demonstrates that the pattern appears to be optical, rather than pigmental, as the effect is only seen at certain angles and distances of light and changes with positions. Pairs are formed after the butterflies have engaged in a dalliance flight for a period of time. Research suggests that there are antennal olfactory receptors for phenylacetaldehyde and the terpene compounds oxoisophoroneoxide, oxoisophorone, and dihydrooxoisophorone, as these compounds elicited some of the strongest electrophysiological responses whether they were presented in natural or synthetic mixes of floral compounds. Males emerge earlier than females, as they are more willing to fly in lower temperatures than females. The causes of this population decline are not fully determined, but there are several possible factors. Since the common brimstone is univoltine, it may have difficulties adapting to changing environmental conditions compared to species that have multiple generations a year.