Page:Harvesting ants and trap-door spiders. Notes and observations on their habits and dwellings (IA harvestingantstr00mogg).pdf/89

 of distinct species, tend to show that, even as things are, they frequently have to fight for their food.

Hitherto, as far as I have been able to learn, only nineteen true harvesting ants have been detected in the whole world, limiting this term to those species which make the collection of seeds the principal occupation of their outdoor lives, and are evidently in the main dependent upon this kind of food for subsistence.

Now if we compare these nineteen species of ants together a very curious fact forces itself upon our notice—namely, that all of them are closely related, so much so that not only do all belong to the same division of ants (the tribe Myrmicineæ), but that with one exception (Pseudomyrma) all would have been placed by the great Fabricius in one genus, Atta, and the one exception is not far removed from it.

We must not forget, however, that, as has been stated, there are other ants which do occasionally collect seeds, and thus appear to show traces of this remarkable instinct; but as far as I have yet seen, it is always possible to distinguish them readily from true harvesters. Still I think it very likely that in hot climates the division between harvesters and non-*harvesters may be bridged over by a complete chain of intermediates. Here two more questions suggest themselves for more complete future solution. (1) Do true harvesters which store seed in granaries ever