According to Forel, this is how the Amazons (Polgergus rufes-cens) go to the "nest of Formica rufa, situated often from forty to sixty meters away and quite hidden. In the springtime and in the summer days the Polyergus workers individually leave their nest and explore the vicinity for great distances, thus discovering the nests of the species which they pillage. It can be stated with certainty that these are scouts, which later become guides." Thanks to the memory of the places which they have scouted, they serve as guides to the phalanx, and this memory is not purely visual, as Fabre believed, but also olfactory and tactile, since, "deprived of its antennae, a Polyergus cannot orient itself. ' '
It is always with the path of an explorer that the establishment of a temporary or a permanent road begins. When the ants are blind they follow the road of the explorer solely by the anten-nary sense, as we have seen in the experiment of Forel with Eciton carolinense. Certain ants with sight indicate the route to their sisters, and leave on it a slight scent from the end of the abdomen. Thus it is with our little Tapinoma erraticum, according to Forel and the experiments of Santschi; and also with Lasius niger, according to Lubbock.
We owe to Cornetz exact experiments upon the way Messor establishes its permanent roads. A nest of these mining ants is found in a poor pla e without herbage or graminaceous plants in the neighborhood. A worker leaves for exploration, and is offered a package of small seeds. The insect profits by the prize, and makes many journeys between the nest and this provender. Other workers go out in turn. Guided, without doubt, by the scent trace of the explorer, they follow the scent of their sister for a certain distance from the nest; then they spread out fan-shaped, and only part of them reach the seeds. In proportion as the number of seekers multiplies the common scent increases. It is not to be doubted, Cornetz justly observed, that the putting out of provender brought about a slow change from a hunting country into a road; then later, in following days, a progressive transformation of the road into a permanent route visible through frequent use.