ANTS AS DOMINANT INSECTS. n 



( >ther species of ants are well-known garden pests. In the United 

 Slates Lasiits amcricanus, Prcnolcpis imparis and Formica snbscricea 

 >< >niftimcs disfigure the lawns and flower-beds with their excavations 

 and untidy castings, while in tropical America the larger leaf-cutting 

 ants of the genus Atta are a serious menace to horticulture. These 

 latter ants defoliate garden shrubs and fruit trees in an incredibly 

 short time. But the greatest harm is undoubtedly done both in tropical 

 and temperate regions by a host of species that have a pronounced 

 fondness for pasturing and guarding plant-lice (Aphides), mealy bugs 

 (Coccidse) and tree-hoppers (Membracidse) on roots, stems or foliage. 

 All these insects suck the juices of plants and their protection must 

 therefore be regarded as pernicious. The honey-dew which they excrete 

 is eagerly sought by all our species of Camponotus, Formica, Lasius, 

 Prcnolepis, Cremastogaster, Myniiica and Dolichoderus, but only the 

 most abundant species of these genera are to be regarded as positively 

 harmful. Such a species is the commonest of all our ants, Lasius 

 niycr, which is known to hoard the eggs of the corn-root louse (Aphis 

 inoidiradicis) in its nests over winter and to distribute the just-hatched 

 young in the spring along the roots of the maize. The noxious char- 

 acter of some aphidicolous species is, however, slightly mitigated by the 

 fact that in the absence of ants the plant lice discharge their sweet 

 excretions on the leaves where, especially during protracted dry 

 weather, it forms a varnish that interferes with the respiration of the 

 plant and affords a favorable substratum for the growth of destructive 

 leaf-fungi. 



Ants are often feared on account of their stinging and biting habits, 

 but these, at least in the United States, have been greatly exaggerated. 

 In reality only a few of our species like the fire-ant (Solcnopsis qcuii- 

 nata ) and the larger harvesting ants ( Pogonomynnc.r barbatus and P. 

 occidentalis) are sufficiently abundant in the neighborhood of human 

 dwellings to be at all formidable. The fire-ant, which occurs only in 

 the tropics and in our Southern States, is very fond of nesting in door- 

 yards and along paths and roads. It is extremely pugnacious, and, as 

 its name indicates, can sting severely. The sting of the larger harvest- 

 ing ants is even more formidable, but these species, confined to the 

 great plains and the deserts of the Southwest, do not thrive in the 

 neighborhood of human settlements. In general it may be said that 

 ants do not go out of their way to sting and bite, but resort to these 

 offensive measures only when their nests are violently disturbed. 



In concluding this chapter attention may be called to the great value 

 of ants as objects of study. No other group of animals presents 

 such a maze of fascinating problems to the biologist, psychologist and 



