areas with these environmental conditions. Other possibilities include a better ability to assimilate resources as an indication of male mate quality. Because ultraviolet coloration is energetically expensive to develop, it could signal high male quality. Mating After the common brimstone emerges from hibernation, it travels towards habitats that contain larval host plants and mates. The brimstone is primarily monandrous, as demonstrated by the presence of usually only a single spermatophore in females throughout the mating season. Pairs are formed after the butterflies have engaged in a dalliance flight for a period of time. When a pair settles to mate, they do not take flight during copulation and remain paired for a long time of up to forty-eight hours. Physiology Vision The common brimstone appears to have an innate preference for certain colours in nectar plants – red and blue inflorescences are common in heavily used nectar sources in some regions. G. rhamni also has a stronger reliance on visual indications such as colour compared with other butterfly species, which rely more on odour. Olfaction The common brimstone has an antennal response to the floral scent compounds of nectar plants, where neural activity in antennal olfactory receptors occurs in the presence of certain compounds. 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. Additionally, these two compounds are present in the largest quantities in the nectar plants utilised by the brimstone, indicating that scent detection could be important for detecting food sources. This would contribute to more efficient foraging in adult butterflies, as odour could act as a cue for finding and distinguishing nectar plants, allowing more energy to be utilised for other activities such as reproduction. Diapause The adult common brimstone overwinters for seven months, remaining hidden and motionless throughout its hibernation. While both sexes have similar egg to adult development times, they differ in the times that they reach sexual maturity. The reproductive development of males begins just after pupal emergence, and continues during hibernation, which indicates that males may not be able to reproduce until after overwintering. For females, eggs remain undeveloped as the butterflies overwinter, and no reproductive development occurs until after emergence from hibernation. The sexes also differ in times of emergence after overwintering. Emergence