How Smart is a Fruit Fly?

This guy right here? This is Drosophila melanogaster, the common fruit fly. Small, gross, annoying, generally something you want to avoid. So why would I want to get up close and personal with one?

Well, good ol’ D. m. is also a model organism. They’re cheap, easy to care for, reproduce quickly, and genetically simple. Biologists have been studying these guys hardcore for over a century, so they understand them really, really well. Pretty much anything you want to know about a fruit fly, it’s out there somewhere.

That’s especially cool for me as an A.I. researcher. The human brain is – as neuroscientists put it – “really friggin’ complicated.” The fruit fly brain? Not quite so much.

For comparison, a human has about 85 billion neurons in his whole body. Cat, 1 billion. Frog, 16 million. Cockroach, 1 million.

Fruit fly? A measly 100,000 neurons.

Pretty simple, right?

Yet this tiny, almost microscopic brain turns out to be surprisingly sophisticated. Here’s what it looks like, courtesy of the Virtual Fly Brain website (yes, that exists):


You can see it has a definite structure: two optic lobes (connected to the eyes) on the far left and right, two hemispheres in the main body of the brain, smaller structures clearly visible.

What does a fruit fly do with 100,000 neurons?

They can fly, of course, navigating around obstacles and searching for food. They can see, hear, smell, taste, and touch – and make decisions based on all those senses. They’re affected by alcohol in much the same way humans are, and can even become “alcoholic,” seeking more and more of the stuff over time. Remarkably, they can even form long-term memories, learning to seek or avoid arbitrary smells based on laboratory training.

In a nutshell: they’re thinking. They’re not reading Hamlet, they’re not self-aware, and who knows if they have anything like consciousness – but they’re definitely thinking.

With only 100,000 neurons. All of which have been painstakingly studied and analyzed for decades. For someone working on artificial intelligence, that’s pretty flippin’ sweet.

I’ve got some studying to do.

9 responses to “How Smart is a Fruit Fly?

  1. I looked up ‘how smart is a fruit fly’ because of a couple of unique behaviours I’ve noticed. Our local groceries produce has a bad fruit fly problem…and that means my house has a fruit fly problem. They are so different from common flys. Their speed of mind seems closer to humans. A common fly seems to buzz around at 100 times faster than a human percetion with zero memory. A single fruit fly will get away from you if you swat at it. A fly seems not to remember the swat. If there’s a cabinet where I’ve killed several fruit flys…they will stop hanging out on that cabinet. Maybe the smell the blood of their fallen comrades and know to avoid it. Even their flight paterns seem more organized. And I started laughing when I read about their ability to become alcoholic. I find more fruit flies in my beer or vodka than water or pop or any other beverage. Poor guys drank themselves to death. Anyway…thought I’d put my observations out there. Nobody else seems to care. I found your post both interesting and informative. Thanks.

  2. Matt what mutated fruit flies are those? Currently have a slight fruit fly problem but they seem more like zombie drones than bigger flies, they keep landing in front of me on my desk where I swat them, several dead ones here right now, they still land near them eve on them, I swat miss, and it will land again 5 seconds later to be swatted again. Annoying little zombies. O god I can’t express how much I loathe fruit flies. I like animals, I even respect insects, showing flies and spiders out the window instead of killing them (despite being arachnophobic).. but fruit flies.. I’d be willing to commit genocide on their species… aaaaaaargh these things annoy me to no end and I can’t find a source. There’s no food in the house, it’s clean here. yet for some reason past week I have a slight infestation, checked pipes etc they are all empty and clean too.. One of these days I will snap and I’ll just bring home a flamethrower.

  3. Sexy…

  4. ❤ I started observing them with a magnifying glass on a piece of fruit I left out. Talking to them lovingly and not having the heart to hurt them. I just moved the fruit outside. Anyway the behavior is interesting, some like to hang out with me and it feels like we have repor. Especially the tiniest ones….like they know I’m going to feed them. Hard to find words for such oddity. However it is happening ❤ glad to see actual studies…there is something here for sure

  5. I set out cups of vinegar with a couple of drops of soup in the mix ,the next day I had alot of dead fruit flies floating at the bottom.So I set out afresh cup of the mix in high hopes of getting rid of my fruit fly problem.To my surprise they will no longer fly into the vinegar,I haven’t caught a single fruit fly since.They have some how learned through the deaths of their friends to stay away from it.This is awesome,I now have a deeper respect for the fruit fly.Also, even the younger ones will not go into the mix,like someone has told them to stay away.

  6. I went searching to find out about these guys because the last 2 days i have been killing them left and right. they seemed very very very <—-not exaggerating) agressive. I'll swat at one and it would weave and dart into my direction once again. So after killing about 30 to 40 in a span of 2 days i decided to eliminate them once and for all…………i strategically set up the vinegar/oil traps throughout the house………guess what happened!!!!!!! THEY ALL DISAPPEARED!!!!!!!!!!!!!!!!!!!!!!!!!!!! GONE!!!!!!!!!!!!!!!!!!!!!! except 1 who died in the trap. It has been 24 hours since i have set the traps and they are all empty………..weird. Even the way the dodge and get away from danger seems kind of odd. Whats crazy is when both my hands are occupied and cant swat at them they try to land on my hands as if they are taunting me to swat at them

  7. For the traps can use any kind of vinegar? I’ve heard cider vinegar, didn’t have that so I used rice vinegar with a splash of water and a couple of drops of dish washing liquid. If that doesn’t work I guess I can try beer

  8. The net is the smartest insect in the world and the most annoying and it also understands English think about it talk to him see what happens I bet he answers he can’t talk so just tell him to go away and he will tell him to stick around and you will guaranteed

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.