Picture of the Week: Scuttle Flies

If the 30 flies above look nearly indistinguishable, you could be forgiven. It took a passion for insects and extreme dedication—hours spent poring over tens of thousands of specimens—for entomologist Emily Hartop to determine that each is actually a species new to science. 

They’re all scuttle flies, tiny creatures in the phorid family that resemble fruit flies and are so ubiquitous you’ve likely encountered many in your lifetime and simply didn’t know it. The photo grid above features their “official mug shots”—that is, baseline pictures that help scientists make the case for why a species should be considered novel, says Hartop.

Differentiating the flies mostly came down to their genitalia, according to Hartop, who is an assistant collections manager at the Natural History Museum of Los Angeles County (NHM). “We are obsessed with genitalia because that is one of the best ways to tell insects apart,” she says. “I spent many hours at the microscope dissecting these flies.” (Sketches that Hartop did of various fly genitalia appear below.) Hartop and colleagues recently published their findings in the journal Zootaxa. 

The fly specimens were collected at 30 sites in the L.A. area as part of a citizen science project called BioSCAN, which the NHM launched in 2012. The project partners with families to turn their backyards into field laboratories.

The main piece of equipment is called a Malaise trap. “It looks like a pup tent,” explains BioSCAN participant Joe Hogg, 70. “It’s flat on one side [and] rises to a peak on the other. There’s a partition in the middle.” The fly enters under an opening at the base, and then zooms upward. It eventually wears itself out trying to escape, dropping into an ethanol vat below. “They are preserved for eternity at that point,” says Hogg.

Once a week on Saturdays, Hogg changes out the ethanol with a new container. Then every six weeks, someone from the museum arrives to collect the used vats. Other than what were likely mischievous raccoons twice tearing the Malaise trap netting, the process has been seamless, says Hogg, a pseudo-expert in such projects. In addition to volunteering for BioSCAN, he and his wife, Aprille, are also participating in a butterfly-surveying program run by the museum and serve as docents at the Los Angeles Zoo.

It’s fitting, then, that the Hoggs now have a scuttle fly named for them: Megaselia hoggorum. (Megaselia is the genus.) All the BioSCAN participants do, actually. “Each of the families was given the opportunity to name their species. We of course suggested to use their last name,” Hartop says. “They loved it. Who doesn’t want a species named after them?” (A few flies were found at sites other than backyards and are named for the location.)

Collecting flies has another benefit, too: It introduces participants to what BioSCAN calls “hyper-diverse small fauna” found in the area. “You don’t have to go to the Amazon, you don’t have to go to a remote area,” says Hogg. “There’s a diversity of life in your backyard.