Ant Trails

0pieces of food brought home

–cells an ant walks from food to nest now (typical of the last 100)

–cells on the shortest possible road to the nearest pile

–longer than the shortest road from its pile

ant food (ants carrying food show it) nest "home this way" scent "food this way" scent rock

Each trip home

one ant carrying food home: how far it walked the shortest road to the nearest pile something you did

Food brought home

pieces per 100 ticks

Run

Speed Map World size

Your hands

Brush Food per pile

Drag on the ground with the chosen tool, even while the ants run. Block their road and watch them find another. With Add food, every click drops a new pile: add as many as you like, anywhere. Piles shrink as the ants carry them off, and when one is gone its trail fades. Food per pile is for the piles you add and for a new start.

Try this

Two roads

A wall with a short gap and a long way round (endless food, as in all the tries below). Ants try both at first; within a few hundred ticks almost all use the short one.

Block the road

Let them settle, then close the short gap. The old trail leads into a wall for a while, until the long road's scent wins.

A shortcut appears

Only the long road is open. When the trail is busy, open the short gap. Do they notice?

Too good a memory

The same, but the scent fades 4 times slower. Old habits now win: most colonies keep the long road for thousands of ticks.

Maze

Three walls with gaps at alternating ends. Harder: trips stay longer than the best road, but they get there.

Ants and scent

Ants Scent fades Fresh for Wander Smell ahead show home scent show food scent

Scent fades: share lost each tick. Fresh for: an ant's scent is strongest just after it leaves the nest or the food and weakens over this many ticks, so the scent tells "how far is it from here". Wander: random turning each step (exploring). Smell ahead: how far ahead an ant smells, in cells. Changing the world size scales the number of ants with its area.

Why it works

Every ant marks the ground with a scent that is strongest just after it left the nest (or the food). An ant that got somewhere by a short road arrives with fresher scent than one that came the long way, so the freshest mark on each spot always points back along the shortest road found so far. Ants follow the fresh scent, which makes the road busier, which keeps it fresh. When a road gets blocked, its scent fades and the next best road takes over. Real ants do this with pheromones; Simon Goss, Jean-Louis Deneubourg and their team showed it in 1989 with Argentine ants and two bridges of different length, and computer scientists copied it to route phone calls and delivery vans ("ant colony optimisation").