Diptera expert Erica McAlister talks to Tom Ireland about the awesome diversity and unappreciated beauty of flies Robber fly (Asilidae), also known as the assassin fly Erica McAlister is senior curator of Diptera at the Natural History Museum (NHM) and published her first book, The Secret Life of Flies, in 2017. Within a few minutes of meeting her it’s clear that I will have to abandon the regular ‘Q&A’ format for writing up interviews in The Biologist. There are more than 2.5 million Diptera specimens in the NHM collections, and as we get coffee and wander around the museum she seems to have a story about each one of them. McAlister starts by describing the collection’s oldest extant fly species, an Asilus crabroniformis (hornet robber fly) from 1680, collected in Hampton Court Palace by the Queen’s gardener. “A lot of the time back then, they were preserved in books, so the colour still looks fabulous,” she says happily. “Flies don’t contain much lipid, so they don’t deteriorate as much as other specimens. Although they are bit squashed, we can still obtain DNA from them.” McAlister is on a mission to change people’s perception of flies as unhygienic, ugly nuisances. The Secret Life of Flies explores how Diptera is among the most successful and diverse groups of organisms on the planet; how they perform essential ecological functions such as nutrient recycling and pollination, and have evolved a truly amazing range of weird and wonderful life cycles and behaviours. She shows me spider-killing flies, fungus gnats and a tiny chocolate midge, one of the few pollinators of the cocoa plant. No chocolate midge equals no US$100bn chocolate industry. “The language we use with flies is so negative and we need to do more to tackle this. We don’t talk about butterflies annoying us like we do flies. And we would never say ‘all primates do this’ if one primate was really annoying or dangerous, but we do say it about hundreds of thousands of different flies.” McAlister points out a botfly that lives in the stomach of rhinos. “We’re so vertebratecentric that we don’t realise what’s really going on,” she says. “There are more species of fly in the UK than there are mammal species in the world, but look at the bias towards [studying] them.” U n i t e d S t a t e s G e o l o g i c a l S u r v e y McAlister says it’s hard to define her role at the museum, as there is “no normal” for curators here. Her main responsibility is to maintain and enhance the biological heritage contained in the collection, but she also travels to provide expertise to research projects overseas, which are often focused on mosquitos, one of her areas of research. “A species of mosquito called Anopheles barbirostris was found to be spreading malaria on some Indonesian islands and not others, so I was asked to help find specimens from the original locality,” she explains. “The type Vol 66 No 2 / The Biologist / 15