Alex Hyde / Orange tip butterfly egg (Anthocharis cardamines) on Cuckoo flower / Lady's smock (Cardamine pratensis). Peak DIstrict National Park, Derbyshire, UK. May.

Nigel Cattlin / Hairy bittercress (Cardamine hirsuta) leaf rosette with pinnate leaves, growing as garden weed. Berkshire, England, UK. May.

Nigel Cattlin / Hairy bittercress (Cardamine hirsuta) growing as garden weed. Berkshire, England, UK. May.

Nigel Cattlin / Common wintercress (Barbarea vulgaris) in field margin. Berkshire, England, UK. May.

Nigel Cattlin / Common wintercress (Barbarea vulgaris). Berkshire, England, UK. May.

Nick Upton / Yellow dung fly (Scathophaga stercoraria) grooming on a Yellow rocket (Barbarea vulgaris) flowerhead, Wiltshire, England, UK, May.

Nick Upton / Yellow dung fly (Scathophaga stercoraria) grooming on a Yellow rocket (Barbarea vulgaris) flowerhead before taking off, Wiltshire, England, UK, May.

Bruno D'Amicis / Kitaibel's bittercress (Cardamine kitaibeli) leaves in old-growth Beech (Fagus sylvatica) forest. Abruzzo, Lazio and Molise National Park / Parco Nazionale d'Abruzzo, Lazio e Molise UNESCO Wor...

Robert Thompson / Orange-tip butterfly (Anthocharis cardamines), male on Cuckooflower (Cardamine pratensis). Brackagh Moss National Nature Reserve, Portadown, County Armagh, Northern Ireland, UK. May.

Robert Thompson / Orange-tip butterfly (Anthocharis cardamines), male on Cuckooflower (Cardamine pratensis). Brackagh Moss National Nature Reserve, Portadown, County Armagh, Northern Ireland, UK. May.

Fabrice Cahez / Wavy bittercress flowers (Cardamine flexuosa) Vosges, France, April.

Dong Lei / Wild flowers (Cardamine tangutorum) Balang Mountain, Wolong National Nature Reserve, Sichuan Giant Panda Sanctuaries - Wolong, Mt Siguniang and Jiajin Mountains UNESCO World Heritage Site, Sichuan Pr...