New Study Unveils Exotic Flies Hiding in Urban LA

Research posts

The common laboratory fruit fly, Drosophila melanogaster, is arguably the most intensively studied and best known multicellular organism—over 16,000 research papers were published in the last five years with the word “Drosophila” in the title. Many other species of Drosophila, though, still surprise scientists. In a study just published in the journal PLOS ONE, a group of researchers led by the American Museum of Natural History and the Natural History Museum (NHM) of Los Angeles County announce the discovery of two species of Drosophila flies never before seen in the United States living in the heart of Los Angeles.

Drosophila gentica, one of the two surprising fly species in urban Los Angeles.  © AMNH/D. Grimaldi

Drosophila gentica, one of the two surprising fly species in urban Los Angeles. 

© AMNH/D. Grimaldi


"Given their great diversity and ecological significance, as pollinators in particular, arthropods are extremely important to city ecosystems. These two flies are remarkable examples of hidden biodiversity in one of the most populated urban centers in the world,” said David Grimaldi, a curator in the Museum’s  Division of Invertebrate Zoology and lead author of the study. "As urban green areas become better recognized for improving quality of life, with parks and lots replanted with native species, and community gardens multiplying, more attention is being paid to species within cities.”

One of the newly noted species, Drosophila gentica, is the second-most common fruit fly found in the Los Angeles BioSCAN traps. This species was described in 1962 based on specimens collected in El Salvador in 1954, the first and last time it’s been recorded anywhere until now.

This study marks the first time Drosophila flavohirta has been seen in the Western Hemisphere.  © AMNH/D. Grimaldi

This study marks the first time Drosophila flavohirta has been seen in the Western Hemisphere. 

© AMNH/D. Grimaldi


The other species, Drosophila flavohirta, has its origin in Australia, but has accompanied transplanted eucalyptus from Australia to South Africa and Madagascar. That might also explain its presence in California, given the popularity of eucalyptus trees and shrubs there. This is the first time the species has been seen in the Western Hemisphere. The two fly species were collected by researchers with Biodiversity Science: City and Nature (BioSCAN), a project of the NHM.

“I was as surprised as anyone when such unusual flies were found in our samples,” said Brian Brown, NHM entomology curator and an author on the study. “But urban biodiversity is an almost unknown frontier.”

How could these species of one of the world’s most studied organisms have escaped notice for so long in a place like Los Angeles? It all depends on how you look. Previous surveys used fruit or other baits to catch Drosophila. The research team suggests that may be why these species were missed—both breed on flowers, not fruit.

The new study used a tent-like insect trap called a “Malaise trap,” made of a fine-screened fabric that intercepts and collects fly specimens. Thirty of these traps were placed in yards and outdoor areas around L.A., including in two gardens and at one school.

“The citizen scientists that host these traps share in the credit for this discovery,“ Brown said.