walked off the edge and then seemed lost, wandering aimlessly around, but Sherlock was fascinated to watch the ants who reached the paper walking across it until they reached halfway, then turning and heading at right angles to their previous path until they came to the edge and then walking off and starting to wander again.
âTheyâre following a path,â he breathed. âA path they can see but we canât. Somehow, the first few ants had laid that path down and the rest followed it, and when you turned the paper around they kept following the path, not knowing that it now leads somewhere else.â
âThatâs right,â Crowe said. âBest guess is that itâs some kind of chemical. When the ant is carrying food, he leaves a trail of the chemical behind. Imagine it like a rag covered in something that smells strong, like aniseed, attached to one of their feet, and the other ants, like dogs, have a tendency to follow the aniseed trail. Because of the drunkardâs-walk effect, the first ant will wander all over the place before he finds the nest. As more and more ants find the honey, some of them will take longer paths to the nest and some shorter ones. As more ants follow, the shorter paths get reinforced by the chemical because they work better and because the ants can get back quicker, and the longer paths, the wandering ones, fade away because they donât work as well. Eventually you end up with a nearly straight route. Anâ you can prove that by doinâ what I did with the paper. The ants still follow the straight-line trail even though it now leads them away from the nest, not towards it, although eventually theyâll correct themselves.â
âIncredible,â Sherlock said. âI never knew. Itâs not ⦠intelligence ⦠because itâs instinctive and theyâre not communicating, but it looks like itâs intelligent.â
âSometimes,â Crowe pointed out, âa group is less intelligent than an individual. Look at people: one by one they can be clever, but put them into a mob anâ a riot can start, âspecially if thereâs an incitinâ incident. Other times a group exhibits cleverer behaviour than an individual, like here with the ants or with swarms of bees.â
He straightened up, brushing dirt and grass from his linen trousers. âInstinct tells me,â he said, âthat itâs nearly lunchtime. You reckon your aunt and uncle can make some space at the table for a wanderinâ American?â
âIâm sure they can,â Sherlock replied. âAlthough Iâm not so sure about the housekeeperâMrs. Eglantine.â
âLeave her to me. I have bottomless reserves of charm which I can deploy at a momentâs notice.â
They wandered back across the fields and through coppices of trees, with Crowe pointing out clumps of edible mushrooms and other fungi to Sherlock as they went, reinforcing lessons that heâd taught the boy weeks before. By now, Sherlock was fairly sure that he could survive in the wild by eating what he could find without poisoning himself.
Within half an hour they were approaching Holmes Manor, a large and rather forbidding house set in a few acres of open ground. Sherlock could see the window of his own bedroom at the top of the house: a small, irregular room set beneath a sloping roof. It wasnât comfortable, and he never looked forward to going to bed at night.
A carriage was sitting outside the front door, its driver idly flicking his whip while the horse munched hay from a nose bag hung around its head.
âVisitors?â Crowe said.
âUncle Sherrinford and Aunt Anna didnât mention anyone coming for lunch,â Sherlock said, wondering who had been in the carriage.
âWell, weâll find out in a few minutes,â Crowe pointed out. âItâs a waste of mental energy to speculate on a question when the