Herts-based lepidopterists Andrew Neild and Mark Sterling have made impressive use of a recent discovery that the pupae of Purple Emperor butterflies glow in the dark using ultra-violet light.

Visiting a site site near Wheathampstead in-mid June, they were excited to locate and photograph a bright blue, fluorescent chrysalis. Even more remarkably, when he returned in daylight two days later, Andrew found a newly-emerged female butterfly still clinging to a sallow leaf next to her empty pupa case. As an added bonus, a male Purple Emperor then appeared while he was watching the female.

It is less than five years since a search for Purple Emperor larvae using UV light found that although the caterpillars did not glow as hoped, the pupae 'shine'  – attributed to a white, waxy coating on the chrysalis.

Thanks go to Andrew Neild for sharing his photographs. He is a Scientific Associate of the Natural History Museum and also author of a two-volume Butterflies of Venezuela.