If you want to make a significant discovery in zoology you usually need to trek through uncharted rainforests or dive a neglected coral reef. However, entomologists at London's Natural History Museum just need to pay attention while at work when a species of insects previously unknown in Europe turned up literally in its Wildlife Garden.
Those of a whimsical nature might suggest the bright but tiny flies wanted to be found so they parked themselves at one of Britain's leading centers for zoological research. More practical minds might wonder if Chryptochetidae are now widespread across Britain, but had to come to the experts to be noticed.
The Cottony cushion scale parasite fly (Cryptochetum iceryae) originates in Australia, where they are appreciated by citrus farmers for the contribution their larvae plays in keeping down Cottony cushion scale (Icerya purchasi), an insect that feeds on citrus plants. Indeed, they are so valuable in this role they have been deliberately introduced to orange-growing countries like Israel and Chile, despite the history of animals introduced to control a pest sometimes turning into a bigger one in a new environment.
Current temperatures notwithstanding, Britain is usually considered too cold to host a major citrus industry, so C. iceryae has not been introduced there deliberately. Nevertheless, the Museum's Senior Curator of Hymenoptera (wasps, ants, and bees) David Notton collected two of the flies during a routine sweep of the wildlife garden's meadow habitat and was struck by their bright metallic colors.
Further investigation led Notton to publication in Dipterists Digest. The flies are just 2 millimeters (0.05 inches) long and have a similar wingspan. Notable features include their large antennae and stout body shape for their size.
I. purchasi is an invasive pest British biosecurity are keen to keep out, and it has been spotted multiple times on ornamental plants people have attempted to import. It seems at least one case slipped through, but fortunately that time the pest arrived accompanied by its predator.
C. Iceryae has never been reported before in the whole of Europe. For Britain, this discovery is not only the first sighting of the species, but the entire Chryptochetidae family from which it comes.
“It’s absolutely fantastic that we’ve identified a new family of fly in Britain,” Notton said in a statement. “It really shows the importance of urban green spaces such as the Museum’s Wildlife Garden. I love spending time with nature and looking out for what’s in my back garden too – it’s great for mental health and there are so many wonderful things to discover.”
The discovery was made in May 2018, but sadly there has been no repeat sightings, at the museum gardens or anywhere else, in the time it has taken for it to be published.