But what does keep caterpillars marching around a rim? I once climbed the ninety-one steps of the Temple of Kukulkán at Chichén Itzá and found, as have many others, that going up the steep staircase is much easier than coming down, which is quite scary. Fabre’s circling caterpillars likely found themselves in a similar predicament, weighing their secure footing on the rim of the pot against a plunge down its steep and smooth sides. In one famous case of similar entrapment, the New York Times reported that in June of 1913, teeming hordes of another social species, the forest tent caterpillar, climbed onto the tracks of the Long Island Rail Road. Rather than go up and over, the caterpillars showed the same reluctance to descend as had Fabre’s. The rails were soon covered with the slippery remains of tens of millions of caterpillars, until eventually the wheels of locomotives spun in place!
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