The Galapagos finches have a problem – and breeding maggots is the solution. (Rosemary Grant/Science via Associated Press)

Nobody keeps maggots in little plastic farms, like they do with ants. Nor do they reminisce about catching maggots in a Mason jar on a warm summer night, as they might with lightning bugs. And I have yet to hear of anyone tucking their kids into bed with a sweet tale of maggot metamorphosis, though these creatures go through the same four-step transformation as other insects with pupal stages, like very hungry caterpillars.

Indeed, the maggot may be one of the least liked creatures on planet Earth.

But what if raising maggots was the key to saving a critically endangered species? Might you be able to look past their plump, repugnant little bodies and their squirmy-wormy writhing?

Paola Lahuatte has. In fact, you might call her the Mother of Maggots.

As a junior researcher at the Charles Darwin Foundation in Ecuador, Lahuatte has spent the last few years conducting painstaking research into the life cycle of Philornis downsi, a nasty, parasitic fly that’s on its way to killing off the last few dozen mangrove finches left on earth.

Mangrove finches, you see, are native to the Galapagos Islands. The parasitic flies are not. As adults, the flies eat fruit and nectar, which is why it’s thought they may have arrived on the island by stowing away in a shipment of bananas. But it’s when these flies produce maggots that the story takes a dark turn.

First, an adult P. downsi seeks out a bird nest where it deposits up to 200 eggs. In a few days, the eggs hatch into the fly’s larval form — tiny maggots smaller than a grain of rice, but similar in appearance.

A medium ground finch (Geospiza fortis) nestling that was killed by Philornis downsi larvae. (P. Lahuatte) A medium ground finch (Geospiza fortis) nestling that was killed by Philornis downsi larvae. (P. Lahuatte)

The maggots wriggle up to the unfortunate chicks in residence, crawl into their nostrils and auditory canals, and use special hooks in their mouths to tear through the chicks’ tender tissues. Then the maggots simply suckle at the wounds like creamy-white chupacabras.// //

“When the larvae get older they move to the bottom of the nest and emerge at night to feed on the nestlings, leaving puncture wounds,” says Lahuatte.

And all this blood-sucking takes a toll. A particularly bad P. downsi infestation can kill all the chicks in a nest — even before the maggots are done developing. When this happens, the larvae shift from stealing the blood of live chicks to simply feeding on their carcasses.

At this point you may be wondering why anyone would want to create more of these ravenous hell spawn. But to put these parasites out of commission, you need to breed hordes of them.

Lahuatte and her colleagues are hoping to breed infertile male flies that they can release onto the Galapagos to disrupt the reproduction cycle of P. downsi. The more female flies in the wild that mate with dummy males, the fewer maggots the birds will have to deal with in the next generation. Scientists call this the “sterile insect technique”, and it is the reason you’ve probably never had to dig a screwworm out of your shoulder.

But here’s the thing: You can’t just forget to take out your trash can for a week and wind up with ten bajillion P. downsi maggots. That’s because these creepy crawlies crave blood. And because ethics standards (and common decency) prevent scientists from letting the maggots go nuts on a captive population of living birds, Operation Black Hawk Downsi has never really panned out.

“The irony is that this fly is so successful in the wild, but so hard to rear in the lab,” says Lahuatte.


An adult Philornis downsi. (P. Lahuatte)

In 2008-2009, other researchers tried to find a way around the live host issue by making all sorts of offerings to the tiny, parasitic gods. They fed the maggots powdered egg whites, powdered milk, ground beef, liver, psyllium, and, er, “throat mucous.” But out of 477 maggots, just three survived to adulthood. And they made it on a diet of chicken blood.

Unfortunately, a lack of funding halted progress for several years, but in 2013-2014, Lahuatte and her colleagues picked up the torch. They set out to see if they could perfect the chicken blood approach. This meant capturing adult flies in the wild and coaxing them to lay their eggs inside a container. Then they’d remove the eggs oh-so-gently using the moistened tip of a paint brush and place them in Petri dishes.

Any maggots that hatched were randomly placed into three groups with a different diet. The first group received pure chicken blood, collected from a local farm as it slaughtered chickens for commercial purposes. The second group received a sort of chicken-blood protein shake — that is, chicken blood mixed with protein, milk powder, iron, calcium, zinc, and vitamin C and D. And group three dined on chicken blood mixed with protein and brewer’s yeast.

In the end, Lahuatte and company were able to raise 41 adult flies from just 385 maggots. (Fifty flies reached adulthood, but nine of these were unable to inflate their wings for some reason.) While different diets didn’t seem to make a significant difference to the survival rate, maggots that were fed the brewer’s yeast developed slightly faster. Overall, the study published Thursday in The Journal of Insect Science yielded a success rate of around 10 percent, a vast improvement over the 0.6 percent survival rate in the earlier attempt.

“We are very excited about this,” says Lahuatte. “Our biggest challenge is getting the flies to reproduce readily in the laboratory and to lay fertile eggs. We need to figure this out so that we can complete the life cycle in artificial conditions.”

If we’re going to save the mangrove finch, progress must come quickly. There are only around 80 to 100 of the birds left in the wild, so few that the Charles Darwin Foundation has taken to breeding them in captivity as a buffer against extinction. And it’s not just mangrove finches that are at stake here. Scientists have documented P. downsi maggots chowing down on at least 15 other species and subspecies of bird on the Galapagos.

This makes every maggot that survives to adulthood incredibly important. And Lahuatte admits that a funny thing happens after you spend all those hours hunched over a Petri dish willing the maggots to survive … You actually start to root for them.

“Not that many people like insects and even fewer people like flies that have larvae that feed on bird blood,” says Lahuatte.

But if nurturing the next generation of P. downsi might help us eradicate the scourge for good, then the ends justify the maggots.

Jason Bittel writes about weird animals for a living. You can find more of his work at his website

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