INTERRELATIONS OF INSECTS 279 



average, though occasionally as deep as 6 feet, and the entire route led 

 with remarkable precisior^to a tree which was being defoliated. 



The same observer has given also a brief account of a leaf-cutting ant 

 that lives in New Jersey. This species (Atta septentrionalis) cuts the 

 needle-like leaves of seedling pines into little pieces, which are carried 

 to the nest. Two columns of workers may be seen, one composed of 

 individuals returning to the nest, each with a piece of a pine needle, the 

 other of outgoing workers. The nest is a simple structure, extending 

 some seven inches underground and ending in a chamber in which are 

 several small pulpy balls, consisting probably of masticated leaves. 

 Further studies upon our own leaf-cutting ants, modeled after the ad- 

 mirable studies of Moller, are much to be desired. 



Harvesting Ants. Lubbock observes that some ants collect the 

 seeds of violets and grasses and preserve them carefully for some purpose 

 as yet unknown. From such a beginning as this may have arisen the 

 extraordinary habits of the agricultural, or harvesting, ants, of which 

 some twenty species are known from various parts of the world. 



The Texas species Pogonomyrmex barbatus, studied by Lincecum 

 and by McCook, clears away the herbage around its nest (even plants 

 several feet high and as thick as a man's thumb) and levels the ground, 

 forming a disk often 10 or 12 and sometimes 15 to 20 feet in diameter, 

 from which radiating paths are made, from 60 to 300 feet in length. The 

 ants go back and forth along these roads, carrying to the nest seeds which 

 they have collected from the ground or else have cut from plants; these 

 seeds are stored in "granaries" several feet underground and are even- 

 tually used as food. The ants prefer the seeds of a grass, A ristida oligantha, 

 but the oft-repeated statement that they sow the seeds of this "ant-rice," 

 guard it and weed it, is denied by Wheeler. 



Notwithstanding the elaborate studies of McCook upon this subject, 

 there still remain not a few essential questions to be answered. 



Myrmecophilism. To add to the complexity of ant-life, the nests 

 of ants, when at all extensive, are frequented by a great variety of other 

 arthropods, which on account of their association with ants are termed 

 myrmeco philes . Most of these are insects, of which Wasmann has 

 catalogued 1,200 species, but not a few are spiders, mites, crustaceans, 

 etc. Though the diverse relations between myrmecophiles and ants 

 are but partially understood, these aliens may for convenience be con- 

 sidered under five groups: captives, guests, visitors, intruders and parasites. 



Captives. Besides enslaving other species, as already mentioned, 

 ants make use of aphids and some coccids for the sake of their palatable 



