Dr Sarah Luke, postdoctoral researcher at the Museum of Zoology, writes:
This elegant little damselfly (with the rather un-catchy scientific name Euphaea subcostalis) is a favourite of mine in the collection, because it reminds me of the time I spent doing fieldwork in rainforest streams in Borneo. The male has a black body, which almost looks velvety, and very strikingly coloured iridescent turquoise and black wings. They often sun themselves on rocks or logs in the stream, and they are easy to spot as their turquoise wings glint in the sun. Absolutely beautiful!
I was lucky enough to come across a lot of them during fieldwork in Sabah, Malaysian Borneo, during my PhD. Borneo – along with many other places around the world – is increasingly affected by land use change, including logging of natural forest habitat for timber, and conversion of forest to agriculture. During my PhD work I was interested in finding out how land use type surrounding streams affects the dragonfly and damselfly community. Because their larvae develop in water, whilst the adults rely on resources from the land, dragonflies and damselflies can be affected by a range of impacts and so can be valuable ‘indicators’ of environmental changes that are happening across landscapes. They also play important roles as predators in and around streams, and as prey for other species, including birds, and so any losses or changes in their community could have big knock-on effects. To determine how land use affects dragonfly and damselfly communities I did surveys in streams running through a range of habitat types including old growth forests that had never been logged, forests that had undergone selective logging of trees to extract timber, and also oil palm plantations, and recorded the species and the number of individuals found in each.
I found that whilst Euphaea subcostalis were very common in the forested streams, these turquoise gems were largely missing from streams that had oil palm right up to the water’s edge. Although there were still lots of dragonflies and damselflies in the oil palm streams, they were a different range of species, suggesting that something about this habitat didn’t suit the needs of Euphaea subcostalis. However, in oil palm streams where there was still some forest remaining on the stream bank (so-called ‘riparian buffers’), I found Euphaea subcostalis again.
It was lovely to have the opportunity to see so many of these beautiful damselflies flitting around the forest, and very encouraging to find that a forest-specialised species can persist if small changes are made to how agriculture is managed. I hope that this glitzy species continues to take centre stage in the streams of Borneo for many years to come!