# The Fly Farm

True story, also posted to https://substack.com/home/post/p-181423349

*CW: farming and eating animals*.

I was twenty in the year twenty-twenty. It was high summer and high covid; in the UK, we were pretty much banned from meeting up with anyone. I'd spent the months since March stuck with my parents and frantically texting a girl with whom I had a feelings-deeply-repressed-but-once-did-hook-up-friendship.

I hadn't heard from my university professors in months, but one of my coursemates had been offered **two** summer jobs. One was remote-work data analysis on domestic dog genomes. The other was hands-on fly farming. She took the first.

"I can't believe you turned down the fly farm!"

"I don't want to work on a fly farm!"

"I do, hang on, can you put him in touch with me?"

So for two and a half weeks, I worked on a fly farm. It was run by a guy I'll call Harry (not his real name) who was amusing but prone to stress, and his fiancée. They were in their mid twenties I think.[^i7ymjlv80a8]

* * *

They were black soldier flies. Not native to the UK, but 'naturalized' meaning that they don't really cause any trouble. The Rethink Priorities Welfare Range Report assigns them a moral weight of 1/77 of a human. Flies are not valuable produce. Adult flies are only valuable insofar as they are needed to produce larvae.

![The Black Soldier Fly: the star of insect farming](https://betterorigin.co.uk/wp-content/uploads/2021/05/shutterstock_1788085229-scaled-2.jpg)

They're quite handsome animals. They don't buzz around your food like fruit flies or bluebottles.

There are two or three valuable things you can do with larvae. Primarily, they're sold as pet food for birds and lizards. They're more nutritious and easier to work with than the more standard mealworms. Mealworms need to be dusted with nutrient powder before being used as pet food, and they produce dust which is harmful to the farm workers.

The second use is waste disposal. Harry was able to get their feedstock for free: it was mouldy oranges from a local food distribution centre. Once or twice a week, we would take Harry's pickup truck and stack it and the trailer with rejected cardboard boxes. Most palettes had only one or two bad oranges, Harry told me he usually ate the rest. The oranges were a major boon because the farm mostly just smelled or oranges, rather than fly.

Rethink Priorities does not provide a moral weight for these larvae. The closest thing may be silkworms, which are rated at 1/500 of a human.

* * *

My days mirrored the lives of the larvae. First, I went to The Fly Rooms. These were where we kept the adult flies. Every inch of wall space was covered by flies. Whenever I entered, the flies were mostly just sitting around, but my first task was to keep the rooms humid. This meant spraying down the walls with water, which dispersed the flies. Many of these would land on me, but I got used to it.

They were the worst smelling part of the farm: adult black soldier flies don't eat, but they do like to lay their eggs around rotting things, so we used rotting wheat germ (kind of like fermenting, mouldy porridge). Each box of rotting wheat germ had several blocks of wood stacked on top.

I would pick up these blocks, and gently, gently scrape off the eggs. The eggs are about a millimetre in size, basically as small as a thing can be for you to still see it. Eggs went into sideways-stacked jars, with a little more wheat germ, not mouldy this time.

These were called "K-boxes" which was short for "kinder". The German word for children that is, nothing to do with kindness. I checked the K-boxes for ones where the eggs had hatched and the larvae had grown to a few millimetres in length. These were moved to the trays, and taken to the main room of the farm.

This room had three large racks, two on the left and one on the right. They went almost to the ceiling. On the racks were trays of grubs. Sometimes, there were too many trays, and we stacked them on palettes on the floor. Usually we did this with the younger ones.

This room really smelled of oranges. The lights were always low, because the larvae prefer the dark. They'd always move to the darker side of the tray. I often thought that I could program a decent simulacrum of one of these larvae. If dark, flee. If touched, wiggle. If food, eat.

Sometimes, the lights were left on overnight by mistake, and the larvae on the top shelves would, fleeing from the light on one side, pile up on the opposing side of the tray and spill out onto the floor. The larvae have very simple behaviour. This happened once when I was there, and I first realized something was wrong when I stepped onto them.

Stepping on the larvae was inevitable, in the course of operations, and not only when a mishap like that had happened. There were literally thousands of them at any one time, and they're not really the kinds of animals you can easily see on a dirty floor. They're quite sturdy, for insect larvae, but not sturdy enough to survive being trodden on. You could feel them popping underfoot; I suppose their toughness meant that when their bodies did burst, the resulting explosion was all the more powerful.

When a whole tray had made a break for it, the proper course of action was to sweep them up, and scoop them back into a tray.

Anyway, the oranges. The oranges were pulped by a giant machine, one of about two useful industrial installations on the farm. Each tray got one large scoop of oranges per day, if the larvae in there had eaten their previous rations. The exception was when the larvae were nearing adulthood; then, we often held back a scoop, so that they would be drier the next day.

* * *

Two final tasks. Trays of large larvae, almost ready to pupate, were selected each day. They had two potential fates. A lucky few were transferred back to The Fly Rooms, where they would pupate, emerge as adults, and fuck like crazy (there's very little else to do in The Fly Rooms). 

The others were to become pet food. This meant separating them from their waste, which had accumulated in each tray. This waste was a mixture of shit and shed skin, and we called it "frass". To do this, we used a device which I called The Grub Vortex. The Grub Vortex was, well:

![A large mesh device oscillates, comically bouncing grubs out of a chute on once side and into a tray.](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/animations/aad2950e211c2e7bea92d4f5885402f2aff9d5cbc3f52342.gif)

Bad and Naughty Grubs Go Into The Grub Vortex

The effectiveness of separation was remarkable. The larvae came out almost completely free of frass, as long as the frass was relatively dry. This was why we didn't feed them for a day or so before they were to be shipped out.

These larvae were packaged up by weight. I then drove them to the local Post Office. They were labelled "Caution, Live Insects". Once, a research institute in Ghana asked for a gram of eggs, for which they paid £90 plus shipping. We never quite figured out why they wanted these, as black soldier flies are native to Ghana.

Our biggest customer was a major pet shop chain. They took orders on Monday. These were packaged by volume, instead of weight, with a little bit of coconut substrate.

* * *

Harry also wanted to sell a kind of "grub popcorn" for human consumption. His fiancée told me they first froze the larvae, to kill them, then microwaved them. Apparently they were really quite nice. Harry also thought about farming bloodworms, small larvae of non-biting midges, since their colour makes them a visually appealing meat substitute.

Most insects are pretty unappealing to eat. They're small and difficult to peel, so unlike shrimp or lobster they're usually eaten with their carapaces still on. With adult insects, like crickets, this usually means that the legs get caught in your teeth. The texture is tough, but not very crunchy. It's bad. You can't even taste the crickets most of the time, since they're usually drenched in seasoning powder.

Ants have an interesting flavour. They're full of formic acid, which is even simpler than acetic acid which is AKA vinegar. Formic acid is literally named after the ants. It gives them a tangy flavour, similar to vinegar. Formate is technically toxic in high doses, but it's unclear whether or not this matters when you're eating ants. Ants are too small for the texture to be unpleasant.

Mealworms are edible. They're just about simple enough to get the flesh out of the carapace. Apparently they taste like shrimp, minus the sea. 

I never got to try the grub popcorn. Harry's fiancée told me it was pretty good. I wonder if the flavour stands on its own.

* * *

It's five years later, and I'm living with the girl from the first paragraph (we un-repressed our feelings once the summer was over) last week, I was looking through animal welfare charities. Seems like, by my estimates, the campaign against cage-free eggs is the best. 

"Why are you donating to cage-free eggs?"

"It's the most effective way to help farmed animals."

"But you don't care about chickens!"

"Yes I do!"

* * *

Black soldier fly larvae have around 36,000 neurons at their largest size. This is about one two-millionth of the number that a human has, or one one-hundred-thousandth of the number that a cow has. A black soldier fly larva yields one one-millionth of the meat on a cow.

The Rethink Priorities Welfare Range Report estimates a moral weight of 1/500 to 1/76 of a person for the larvae and flies I worked with. This many larvae fit into a single tray, and can be packaged up and sent to pet shops in about an afternoon.

I don't know whether the larvae on our farm were living "the good life". Certainly, being kept in a tray seems unpleasant, but it's not like the flies had lofty ambitions for their lives. Being kept in a tray which also contains everything you could ever need, want, or dream of (that is, orange pulp) doesn't sound so bad.

Freezing invertebrates is usually considered the most humane way to kill them. Unlike humans, they don't have any ways to keep themselves warm. They can't shiver. Prevailing wisdom is that their nervous systems just slow down like any other chemical reaction, without much in the way of a stress response. Then they die. Being eaten by a pet lizard sounds much less pleasant.

As I alluded to earlier, most insect larvae have only one response to threats: they wiggle. Presumably, the primary threat to an insect larva is being picked up by a predator, like a bird, and wiggling is the best way to escape. They also wiggle if dabbed with capsaicin, sometimes.

I can attest that wiggling sometimes works. Last autumn, I spotted a local cat[^j9irl75bz9] pawing at something and looking extremely alarmed as it did so. That something was a lime hawk-moth caterpillar, wriggling like mad, but unharmed. I rescued the caterpillar, allowed it to pupate in some soil, and it is currently spending the winter in my fridge, in a tupperware on the shelf I also use for steaks and cheeses.[^b70wo8fvmas] Occasionally, I pick it up to check on it, at which point it, you guessed it, it wiggles a bit.

What is the moral weight of five-hundred `if-then-else` clauses?

![undefined](https://upload.wikimedia.org/wikipedia/commons/8/89/Lime_hawk_moth.jpg)

[^i7ymjlv80a8]: Harry and his wife were, barring the flies, vegan, as far as I remember. 

[^j9irl75bz9]: Cats have around the same brain size as cows. 

[^b70wo8fvmas]: I am not going to eat the moth. My hope is to release it next Spring.