Brimstone Gonepteryx rhamni (Linnaeus 1758 )
Family: Pieridae, subgroup Coliadinae (The Yellows)
Common and becoming more widespread and abundance determined by the presence of one of its larval foodplants . It is a strong , fast flying, far ranging species that can turn up in almost every corner of our county. However they do come together to form colonies often in woodlands where they will overwinter. The species is not under threat.
The maps illustrate Purging Buckthorn preference for limestone along the Magnesiam limestone ridge, The tabular hills on teh south side of the North York moors and the Craven limestones on Inglebrough, Grassington and Bastow. Alder buckthorn prefers the wetlands of the Humberhead levels.
Buckthorn is a rare plant but widespread which accounts for the Brimstones gypsy lifestyle. Alder Buckthorn is acid-loving, being found in damp, marshy areas or as an under-storey in open woodlands. Sometimes associated with old woodlands where it was grown to produce gunpowder charcoal. Often confused at the bud and young leaf stage with alder which also prefers the wet. It grows mainly as a shrub, only occasionally reaching as high as 5-7m (15-20ft) and tolerates partial shade. It has also been widely planted as part of new hedgerow in the stewardship scheme and by local authorities, nature reserves biodiversity projects and wildlife trusts
Purging Buckthorn thrives best on poor, dry, chalk and limestone soils. It is thorny and can be used in hedging but grows into a tree 3-10m (10-30ft) in height. It is found along woodland edges and in scrubby areas and hedgerows.
Buckthorn ID Tips
Common or Purging Buckthorn Alder Buckthorn
Common buckthorn leaves are hairless, have toothed edged and curved veins (left two) and leaves have a pointed tip; while alder buckthorn leaves are glossy have smooth edges and parallel veins and red/brown petioles (right two) Alder buckthorn is also easily confused with young common alder and share the hairy karki coloured shoot tips and also grow in the same habitat. Both species are often confused with Dogwood.
Conservation Gardening Tips
If you plant a young plant in your garden you are nearly guaranteed more regularly visits and the delight of watching the eggs develop into caterpillars from April- Late July
Abundance Scale =
The northern limit of the species in Britain lies mainly across Yorkshire and Cumbria, and into Northumberland, with the occasional very rare sighting into Southern Scotland in more recent years.
Very mobile, hibernating resident. One brood, with butterfly stage lasting up to 12 months (approx Jul/Jul).
The majority of tetrad records represent single sightings of wanderers, whilst tetrad clusters indicate areas of foodplant availability where regular breeding takes place. The Brimstone is a butterfly invariably seen one or two at a time and even in its hotspot areas, site counts (covering up to 1km square) are rarely above the 10/30 range. The butterfly has been recorded in every month of the year and increasingly reported earlier (Feb/Mar) and later (Sept/Oct).
2019 was an excellent year with numbers much higher than any in the past 10 years. Good sites in Yorkshire where this species has been regularly seen over the past couple of years are North Cave Wetlands, Strensall Common , Brockadale , Bishop Wood , and Nosterfield Nature Reserve .
Adults spread widely so it is not surprising we see them but finding their rare foodplant necessitates constant searching. After wintering in woodlands males emerge first and hunt for females. Eggs are placed on leaf buds at the shoot tip and the underside of the youngest developing leaves of foodplant leaves . At first blue through green and then later pale cream bottle-shaped eggs are quite conspicious and are only laid on Buckthorn species.
Females will spend time testing the plant selecting those in fairly good light and healthy and she will return many times over the spring monthes into summer. They tend to choose smaller plants away from others in an attempt to avoid predation by particularly blue tits who will home in bigger plants with more caterpillars. Mortality rates can be very high.
Eggs are laid from April to July and hatch after about 10 days. At first pale pale yellow larvae feed on the underside of the youngest leaves but rapidly grow and later instars are darker green larvae take around a month and 5 instars to mature and usually leave their buckthorn to pupate in low vegetation.
Adult butterflies emerge after about 2 weeks and can remain active until the end of Sept or later, returning to their woodland home then can re-emerge to take advantage of good conditions to build up reserves. In very hot years they rarely reappear unless nectar is abundant.
The species shows a strong preference for purple flowers when nectaring, and its long proboscis is well-adapted to feeding on flowers like Teasel Dipsacus fullonum. Brimstones often hibernate under evergreen leaves, especially Holly or Ivy. They may 'test' the air on warmer winter days and visit ‘Pussy’ Willow catkins Salix sp or early Dandelions in search of a top-up nectar feed.
Photo by J Bone
Photo by Nyree Fearnley
Photo by Nyree Fearnley