Young Sherlock Holmes_ Red Leech - Andrew Lane [3]
Sherlock just smiled and shook his head.
‘Honey is largely sugar, plus a whole load of other things,’ Crowe continued. ‘Ants love sugar. They take it back to the nest to feed the queen, and the little grubs that hatch from the eggs.’
Dipping his finger in the honey, which Sherlock noticed was runny in the heat of the morning sun, Crowe scooped up a huge shiny droplet and let it fall. It caught on a clump of grass and hung there for a few moments before strands of it sagged to the ground and lay there in scrawled and glistening threads.
‘Now let’s see what the little critters do.’
Sherlock watched as the ants continued in their random wanderings; some climbing up strands of grass and dangling upside down for a while and others foraging among grains of dirt. After a while, one of them crossed a strand of honey. It stopped midway. For a moment Sherlock thought it was stuck, but it wandered along the strand, then wandered back, then dipped its head as though drinking.
‘It’s collecting as much as it can carry,’ Crowe said conversationally. ‘It’ll head back for the nest now.’ And indeed the ant did appear to retrace its steps, but rather than heading directly for the nest it continued to wander back and forth. It took a few minutes, and Sherlock almost lost it a couple of times as it crossed the path of other groups of ants, but eventually it reached the pile of dry earth and vanished into a hole in the side.
‘So what now?’ Sherlock asked.
‘Look at the honey,’ Crowe said.
Ten, perhaps fifteen ants had discovered the honey by now, and they were all taking samples. Other ants kept joining the throng. As they joined, others broke away and headed vaguely in the direction of the nest.
‘What do you notice?’ Crowe asked.
Sherlock bent his head to look closer. ‘The ants appear to be taking a shorter and shorter time to get back to the nest,’ he said, wonderingly.
After a few minutes there were two parallel lines of ants heading between the honey and the nest. The random wandering had been replaced with a purposeful direction.
‘Good,’ Crowe said approvingly. ‘Now let’s try a little experiment.’
He reached into his pocket and took out a scrap of paper about the size of his palm. He laid it on the ground halfway between the nest and the honey. The ants crossed the paper back towards the nest as if they hadn’t even noticed it.
‘How are they communicating?’ Sherlock asked. ‘How are the ants who have found the honey telling the ones in the nest where it is?’
‘They’re not,’ Crowe answered. ‘The fact that they are returnin’ with honey is a signal that there’s food out there, but they can’t talk to each other, they can’t read each other’s minds and they can’t point with those little legs of theirs. There’s something a lot cleverer goin’ on. Let me show you.’
Crowe reached down and deftly turned the scrap of paper through ninety degrees. The ants already on the paper 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 reached the edge and then walking off and starting to wander again.
‘They’re following a path,’ he breathed. ‘A path they can see but we can’t. 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.’
‘That’s right,’ Crowe said approvingly. ‘Best guess is that it’s 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 strongly, 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 “drunkard’s walk” effect, the first ant will wander all over the place before he finds the nest. As more and more ants find the