Ants Can Smell Almost Anything

The sense of smell is remarkably acute in all ants—at least equalling that of dogs.

The outstanding ant odor is that of formic acid, which is somewhat like that of illuminating gas, exuded from the bodies of all species. But this is only the smell of the race. It must be subject to an infinite number of variations to most of which ants alone are sensitive. They know their comrades, even after a long separation. Famed naturalist Sir John Lubbock once returned some ants to their old nest after a separation of 21 months. They were amicably received and evidently recognized as friends. On the other hand if a strange ant is placed in a nest of her own species she is at once attacked.

Dr. William M. Wheeler insists that even the human nose can detect some different species and even, in a few cases, different castes by their odors. Thus, over and above the formic acid smell, the smell of one species suggests ether, of another lemon-geranium, and of still another rotten coconuts.

At least one species of ant has three distinct odors: 1. A scent deposited by the feet, forming an individual trail by which she retraces her own steps. 2. An inherent odor of the whole body which is identical for all of the same lineage and a means of recognizing blood relatives. 3. A nest odor, consisting of the commingled odors of all members of the colony, used to distinguish their nest from the nests of aliens.

Evidently the odor of ants changes with age. It has been pointed out that “a cause of feud between ants of the same species living in different communities is a difference of odor arising out of difference of age in the queen whose progeny constitute the communities.” Ants apparently not only differentiate the innate odors peculiar to the species, sex, caste and individual, but also the incurred odor of the nest and environment. As worker ants advance in age their progressive odor intensifies or changes to such a degree that they may be said to attain a new odor every two or three months.