A CHECKLIST OF THE ANTS OF MONTANA BY

The history of myrmecology in Montana probably began in 1913 with Wheeler’s description of Formica subpolita from Helena and 1914 when he described a new species, Manica hunteri from Gallatin County. A considerable hiatus ensued until 1932 when Cole recorded Pogonomyrmex occidentalis from Custer County. In 1973 Borchert and Anderson published a thorough ecological analysis of the ants of the Bearpaw Mountains, one of the small ranges, which is mostly in Hill County. Thirty-three species were reported. In 1984 Youngs and Campbell published the results of a study of ants preying upon the western spruce budworm near the western border. They reported 4 species of Camponotus and 7 species of Formica from 3 localities in Missoula County and one in Sanders County, but they failed to indicate which species was taken in which locality. These records are indicated by YC. Six other authors have contributed a few records each. From Wing we got four records as spots on maps. D. R. Smith contributed three species for the whole state. Five records are represented by gifts of specimens from Creighton. Finally we are greatly indebted to Roy R. Snelling for sending us 63 additional records based on specimens in the Los Angeles County Natural History Museum. During the summers of 1956, 1961, 1963, 1964 and 1965, while we were still at the University of North Dakota (Grand Forks), we made seven field trips into Montana to observe and collect ants in 32 of the 56 counties. These expeditions yielded a total of 151 records in 64 species. (A record is a species in a locality.) From all these records we extracted a list of 76 species of ants for the state of Montana.


Psyche
THE BIOMES OF MONTANA Our usual guide to biomes is Odum's map, but this time it has failed us, for it puts the whole of Montana in the Grassland Biome.
Only the eastern third is in that biome and is continuous with the Grassland Biome in North Dakota. The middle third might be considered ecotone between the Grassland Biome and the Coniferous Forest Biome of the western third, for the prairie is broken by many small mountain ranges, which are outliers of the Rocky Mountains and the Coniferous Forest Biome. In the western mountains the timberline is at about 9500 ft in the south to 6000 ft in the north. Above that is the Alpine Biome.
With only limited ecological data we have made no attempt to list the ants which characterize each biome.  (Smith 1979). The species in each genus are arranged alphabetically except in Formica where they are first divided into speciesgroups; here we do not follow Smith, because we have transferred the microgyna species-group into the rufa species-group.
The localities in which a species has been collected are grouped by counties (see Figure 1) which are arranged alphabetically. The localities represented by our collecting are preceded by an asterisk. Those in the Borchert-Anderson study are followed by (BA); those of Youngs-Campbell by (YC); those from Snelling by (LA). (See introduction.) Others are followed by the name of the author and year of publication of the book or article. Finally the elevation above sea level is given wherever known.  Figure 2. Thatching ant mounds are conspicuous features of the grasslands. This is partly due to the size of the mound itself, but also to the fact that vegetation around the nest is taller than that of the surrounding prairie. Most of the nest is underground, but it is surmounted by a dome-shaped thatch mound. A typical mound is about 25 inches (66 cm) in diameter and 12 inches (30 cm) high. It is constructed of twigs, grass blades, dried herbaceous stems or any other slender bits of material, assembled by the workers from neighboring vegetation. The thatching ants collected in Montana are Formica haemorrhoidalis, F. obscuripes, F. obscuriventris and F. oreas. the grasslands. A typical mound is conoidal or paraboloidal, 24 inches (60 cm) in basal diameter and 51/2 inches (14 cm) high. It is composed of excavated soil and covered with a layer of fine gravel collected by the workers from the surface of the surrounding soil. A mound is rendered more conspicuous by a circular bare area which surrounds it. These areas average 5 ft (1.5 m) in diameter. The mounds of P. owyheei are similar.
OBLIGATORY SLAVE-MAKERS. Obligatory slave-makers are incapable of performing any of the nest-functions and are therefore wholly dependent upon their slaves. The story of how they raid the nest of some species of Formica to get their slaves is fascinating but too long for this essay. The Montana slave-maker was Polyergus breviceps and its slave was Formica subsericea.
FACULTATIVE SLAVE-MAKERS. These are in the genus Formica and they enslave other species of Formica. They are, however, capable of performing all necessary nest functions; hence they can, and often do, get along without slaves. The species of this group that have been taken in Montana are the five species in the sanguinea species-group. The reported slaves were F. fusca and F. lasioides. nAaVESTIYG AYTS. These ants collect seeds when they are abundant and store them in the nest to be consumed in times of scarcity. Montana harvesting species are Pogonomyrmex occidentalis, P. owyheei and Veromessor lobognathus. The last named species is--for us--the most interesting Montana ant. During the ten years preceding 1965 we traveled 50,000 miles to observe and collect ants in all the continental states (except Alaska) and provinces (except Saskatchewan) north of Mexico and west of the 100th meridian and did general collecting in all biomes. We were, however, especially alert for V. lobognathus ever since we had discovered it in North Dakota in 1955 (Wheeler and Wheeler 1956). "We suspected that if this species occurred in southwestern North Dakota and on the western border of South Dakota, it might also be found in southeastern Montana. Consequently our first stop was at Ekalaka, where we called upon Mr. Marshall Lambert, Director of the Carter County Museum. As a paleontologist Mr. Lambert is thoroughly acquainted with the region. We described the desired habitat. He showed us on our contour map where to go and how to get there. Within 15 minutes after we arrived at the place he had recommended, we found a nest of V. lobognathus." (Wheeler and Wheeler 1967.) As in the Dakotas this nest was on a treeless south-facing slope where much of the surface was bare. The slopes were always near junipers which were on the north-facing slope. This species is a characteristic inhabitant of the Pinyon-Juniper Biome.