Fruit Fly

A whole fruit fly nervous system, alive in a world you can walk into.

The specimen on the plinth is the complete central nervous system of an adult male Drosophila melanogaster: 164,587 neurons and 25,563,197 connections from the MaleCNS v1.0 connectome. Every neuron is a leaky integrate-and-fire unit stepped on the GPU, wired by the dataset's own synapse counts and transmitter predictions, and drawn where its cell body actually sits. A neuron brightens when it fires, so the cloud is the readout.

The fly walking the arena floor is driven by that network, and nothing else. Nothing about it is scripted.

Your first minute

A card meets you when you arrive and walks you through four steps: reset the network, watch the proboscis motor neurons, stimulate the tarsal taste pegs, then look at the fly. Its proboscis comes out. The signal that put it there crossed a real connectome to get there.

After that, open the Experiments panel and press RUN on any of the five protocols. Each one resets the network, drives it on the network's own clock, and prints a verdict from the numbers it measured. Press COMPARE to lay two runs over each other.

The bench

The Fruit Fly Lab window is where you drive the brain by hand.

• Name any set of neurons by cell type, type prefix, class, superclass, side or index, or tap one of the chips for the common ones.
• Stimulate it at a rate you choose, silence it, ablate it, or put it back.
• Watch any group as a live rate, a bar against an honest scale, a scrolling trace, or a spike raster when the group is small.
• See which classes are hot right now, and which drives are running and who owns them.
• Point at the cloud and press ID to name the neuron under the pointer: its cell type, class, superclass, side, transmitter and out degree, with one press to select that whole type.
• Turn the synaptic gain, the time scale and the minimum synapse count, and watch the network change regime.

The five experiments

1. Taste to the proboscis. Drive the 50 tarsal taste pegs at 100 Hz. The two proboscis motor neurons answer within a few hundred milliseconds and the mushroom body stays quiet.
2. Auditory control. The same drive on Johnston's organ instead. Nothing reaches the proboscis, which is how you know the first result was the wiring and not the stimulus.
3. Gain recovery. Sweep the gain and the connection threshold. Too low and nothing arrives, too high and the whole network runs away.
4. Looming and escape. Walk your avatar at the fly. Its looming detectors fire, the giant fibre bursts, and it jumps. Silence LPLC2 and try again.
5. Ablation. Take the Kenyon cells out, or one side of DNa02, and run the taste drive against the intact result.

The fly

Front feet on a sugar disc drive the tarsal taste neurons, one side at a time, so a patch off to the left gives the steering neurons the asymmetry they need to turn toward it. Labellar bristles take over when the proboscis reaches the food. Leg motor neurons walk it, DNa01 and DNa02 turn it, the wing power muscles beat its wings, and a giant-fibre burst throws it into the air. A ring on the floor marks the arena its own escape circuit keeps it inside.

Controls

Action	Keyboard and mouse	Controller	Touch
Move	W A S D	Left stick	On-screen stick
Look	Mouse	Right stick	Drag
Jump	Space	South	Jump
Sprint	Shift	Left stick click	Sprint
Open the bench	L	Start	Lab
Name a neuron	Left click	West	ID
Move between bench controls	Arrows or Tab	D-pad	Tap it
Nudge a slider	Left and right arrows	D-pad left and right	Drag
Activate a bench control	Enter	North	Tap it
Open the experiments	P	Select	Experiments
Run the selected protocol	R	Right trigger	RUN
Next and previous protocol	N and B	Right stick click	Tap it
Compare two runs	C	Left trigger	COMPARE

Put the fly in your own world

Everything here is one installable package, fruitFly. Install it from ZeroMind and add a FruitFlyBrain, a FruitFly, a FoodPatch or two, a FruitFlyLab and a FruitFlyExperiments to your scene. The package README and its experiments guide cover the model, the wiring and the regime it is calibrated to.

Every cell type, class and constant named anywhere in this world is the dataset's own. Nothing about the biology is invented.

Data: MaleCNS v1.0, https://male-cns.janelia.org/, CC-BY 4.0 (HHMI Janelia FlyEM, Google Research and the Cambridge connectomics group; Berg et al. 2026, Cell). Model constants: Shiu et al. 2024, Nature.