High Altitude Ants of the Southern Blue Ridge

Abstract

Four subfamilies of Formicidae, representing 62 forms and 22 genera were recorded above 3500 feet elevation in the southern Blue Ridge Province. A total of 192 collecting trips was made, resulting in 1124 collections. The low average of collections per collecting trip reflects the paucity or lack of ants in certain areas at higher elevation. The ecology of the ant fauna is described in terms of a) altitude, b) forest type, c) nesting site, d) slope exposure, e) degree of slope, and f) percentage of canopy. Ant assemblages could not be satisfactorily defined by any one or several of these environmental factors or variables. Percentage of canopy, which best indicates temperature and moisture conditions at the microhabitat level, was used in describing quantitative population variations. The number of ant forms, and in most cases the number of colonies, decreased with increasing altitude. The exceptions are listed. The most widely preferred nesting site was under rock, either in forest or in the open. Many forms have a wide tolerance: some occupy many or all of the recognized sites. Nests were distributed most frequently on the west, southwest, and south slopes. Colonies were seldom found on steep slopes of more than 75?. No variation in ant distribution could be attributed to the small range of latitude studied. The most common and conspicuous ants were: Aphaenogaster rudis picea, Lasius alienus, and Formica fusca. The altitudinal subspecies, Aphaenogaster rudis picea and A. r. rudis, were both retained as valid forms until further work proves or disproves their validity. Stigmatomma pallipes montigena could not be separated from S. p. pallipes and all Stigmatomma were included under the latter name. Insolation, affecting moisture, relative humidity, rate of evaporation, and temperature of the nesting site is seen as an essential factor in the establishment and success of a colony. Altitude, forest type, nesting site, and slope exposure, are important only as they reflect temperature and moisture conditions.