The photo (above) shows a green sweet that has been discovered by ants on a paved path in my garden. The sweet had been dropped several hours before, and had attracted the interest of an ant colony which was carrying it away. But the pattern of the surrounding plant debris is a mystery. What accounts for its arrangement around the candy?
鈥� The smaller pieces of debris have been dropped by foraging ants which have discovered the much more valuable sugary sweet on the ground. The larger pieces, leaves and sticks, have been trapped in the moraine of small fragments.
John Davies, Lancaster, UK
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鈥� The ants account for the arrangement of leaves around the candy. I know this because I used to watch the ants in my last house build similar structures around tasty morsels of food. There being no leaves handy in my home, the ants would do me the great favour of collecting up cat hair, lint, pieces of thread and suchlike to construct their little fortresses. They would weave the hairs together very nicely too.
鈥淎nts build structures like fortresses around tasty morsels of food in order to defend them鈥�
They do this in defence of the tasty sweet, and only if the food particle justifies the effort 鈥� if it is something they enjoy a good deal, and is too large to be hauled off in just a couple of trips.
I watched carefully to see if they seemed to be using the barrier as scaffolding, to make it easier to reach the food and demolish it, but they did not appear to be doing so. This suggests the purpose of the debris is to keep some competitor away from the ants鈥� prize.
I am not sure what competitor this behaviour evolved to thwart, but I can assure you the cat-hair fortresses would have no deterrent effect on my cat, should he decide he wanted their treat.
Alyson Irvin, Nashville, Tennessee, US