In Defense of Flies

Just in time for wrapping up spooky season, I was having a conversation with myself about flies. This time of year, flies are about the only insects I still see out and about.

They get especially crafty with finding their way into the warmth of a human house, further perpetuating their reputation of being a pest. I realized I’ve become somewhat tolerant and respectful of the flies since starting beekeeping.

This is certainly not a stance I’ve taken my whole life. I never used to be the kind of girl who would stick up for the flies. I hated them as much as anyone, maybe more because as a friend to bugs, I thought flies ruined it for the rest of the insect community. Why couldn’t they have a little bit more class and be useful like the others?

Even I can’t believe I’m writing this. What defense could possibly exist for these schemers who always seem to be sitting close by, rubbing their little hands together and plotting how to best get on our nerves? However, nature does not keep anything around that doesn’t have a use.

Pollination & Pest Control

If you’re into pollinators, it’s hard to ignore their usefulness. As incomparable in looks as they are to the graceful butterfly, flies are actually the better pollinators. In fact, flies are only second in pollination to bees. Without these essential little creeps, we’d be enjoying a whole lot less delicious plant matter.

Another role we can be grateful to flies for is their role in controlling other pests. Yes, pests control pests, this is the circle of life. So while flies are disgusting, if we did away with them we would be dealing with a lot more destructive insects, like worms (European corn borer), caterpillars (Gypsy moth), and beetles (Colorado potato beetle).

They even go after their own by parasitizing other flies, like the common house fly or the cabbage root fly. That means without flies, we would have more flies. Yikes.

No one does a better job of living up to the height of Halloween spook like the fly. Some might argue that blood-sucking bats are a worthy mascot or the spider with her iconic web-spinning capabilities.

Certainly, these creatures are the better-known representatives of Halloween, but their ties to fright and gore are loosely associated and I think the fly deserves some recognition for their all-encompassing disgust factor.

Parasitoid Flies

Parasitization, while a mouthful, is fascinating. If you’re into horror, no scriptwriter, producer, or actor holds a torch to nature’s imagination. The tachinid fly is the most well-researched parasitoid used as a biological control agent (meaning pest murderers). Tachinids, along with other parasitoids, are very specific about who they choose to be their host. They don’t go laying their eggs in just any old caterpillar larvae. Each species of tachinid (8,000 of them) has a species that it thinks is most delicious.

With highly advanced senses and chemical cues, the tachinid mum finds the host insect, lays her eggs nearby, or sometimes directly on (or in) the host. Their eggs will hatch within the host and begin to feed on its tissues while it’s still living. Some parasitoids will paralyze the host and then proceed to feed, while others allow their host to continue doing its own thing. How gracious.

About 70% of tachinid hosts are Lepidopterans, moths and butterflies. Orthopterans are the next group, which are the grasshopper, cricket, and katydid family.

Flesh Flies

Some baby flies start their lifecycle, hatching from their egg, to the sweet smell of decaying flesh, which their mother so lovingly laid them in after careful consideration about whose rotting body was best suited for her youngsters.

They will feed on the dead tissue of the carcass, which basically makes them flesh-eating zombies. What makes flesh-eating flies (from the families Calliphorodae and Sarcophagidae) more metal than zombies is that they play a huge role in breaking down and returning nutrients to the soil so that things like plants and soil organisms can use them. Think of them as meat composters.

If you’re into all the crime drama available on TV then you may already be on board with the “don’t hate flies” campaign. Because flesh-feeding flies are some of the first to colonize a body after it dies (or is murdered), they are used as an indicator in murder investigations to determine the time of death and if the body was moved.

Another disgusting/interesting reason to not hate flies is maggot therapy. While it sounds like a form of torture, it’s actually an incredibly useful method used for healing wounds that haven’t responded well to antibiotics or surgical options.

The more medical, but still gross-sounding term is larval debridement therapy (LDT). It works by inserting sterilized maggots into the wound, where they selectively feed on the dead tissues, leaving the healthy, alive tissue alone.

While it’s completely safe (more than surgical options) and highly effective, the very thought of allowing someone to put bugs in your open wound keeps many people from benefiting from this therapy. Upon researching this therapy for this article, ChatGPT so lovely put it as “psychological discomfort.” Horror movies have done us no favors over the years in destigmatizing the therapy either.

Don’t Poo-Poo the Flies

Other fly moms prefer the cozy home that feces provides their young, which is yuck. You might ask yourself why anything needs to feed on poo at all? Why not just leave it to let it decompose without anything having to eat it?

The fact is that something has to eat it. If maggots don’t eat it, microbes eat it. We just don’t see this happening because they are too tiny. However, maggots (fly children) decompose things about 50-70% faster than microbes alone.

Not only do maggot babes break it down faster, but by competing with the microbes that also want to eat feces they reduce numbers of harmful bacteria. Black soldier flies breaking down waste in countries with improper waste management systems have been used as part of the solution. We think of flies as agents that spread disease, but in a lot of cases, they do the opposite.

Mimicry

You no doubt have seen a fly in your life and thought it was a bee. In fact, I might have tricked you into clicking on this article because you thought the featured picture was a bee.

Aw, there she is.

Black and yellow stripes don’t always mean bee. While fooling humans into thinking they are bees has definitely saved a few of them from the fly swatter, their original intent with mimicking bees was to protect themselves from predators.

I know you know that insects and animals use colors to signal their toxicity, and you probably know that some animals capitalize on this by displaying bright colors when they aren’t toxic. This copying is called Batesian mimicry, named after the guy who discovered it, as per usual.

Perhaps I’ll write something about how to spot the difference because it’s quite easy if you know what to look for (fly eyes, itty-bitty antennae, two wings).