[Photo] The Idioneurula donegani, a new butterfly species

A new species of butterfly has been found during an expedition to an unexplored region of the high Andes of South America.

The coffee-brown butterfly was found by scientist Blanca Huertas, who is butterfly curator at the Natural History Museum.

Because of the difficulty of the terrain Huertas and her team and their equipment were dropped by helicopter on to an isolated peak at 3,000 metres above sea level.

It was the first time people have explored the highest elevations of the 100 kilometre-long mountain range in Colombia's Serran??a de los Yarigu??es. and led to it being designated a national park by the Colombian government.

The butterfly was named Idioneurula donegani in honour of Thomas Donegan, project director of Evaluation of Biodiversity in the Andes (EBA) who pioneered the expeditions.

The medium-sized butterfly has eyespots on its hindwings and resembles three other species of Idioneurula butterflies with yellow and orange outlines on the wings.

It lives in the high elevation 'paramo' forests of Colombia, characterised by ferns, orchids, palms and grasses and is an endemic species of the Yarigu??es mountains in Colombia, which means it is not found anywhere else in the world.

The new species was found at two different locations at the top of the mountain range and has been recommended for IUCN categorisation as vulnerable.

Blanca Huertas,said: 'This is an amazing discovery. Butterflies are a diverse group of insects with almost 20,000 known species, 40 per cent of which are in South America. We have been to almost every corner of the world and although some remote parts of the Neotropical region remain unexplored, we only occasionally discover a new species.'

Butterflies found during the expedition were examined and compared to specimens held in the Natural History Museum's collections, which include more than 7,000 species of butterflies from South America. Molecular analysis of DNA collected from the butterflies in the field revealed that I. donegani is a separate species.

'New finds like this encourage us to keep exploring the world', said Huertas.

'We have only recently explored the mountain where we found I. donegani. Other remote and unexplored mountains like the Yarigu??es could have other species that remain undiscovered. We are privileged at the Natural History Museum to have one of the largest butterfly collections in the world. We look after 28m insects here, which include around 3m butterflies.'

The paper describing the new species was published this month in the prestigious international journal Zootaxa and is available online (www.mapress.com/zootaxa/2007f/zt01652p040.pdf).