FORAGING ACTIVITY, TRAILS, FOOD SOURCES AND PREDATORS OF FORMICA OBSCURIPES FOREL (HYMENOPTERA, FORMICIDAE) AT HIGH-ALTITUDE IN COLORADO

The thatching ant, Formica obscuripes Forel, was studied at high altit ude in Colorado by marking workers and flagging trails. Mounds had 1-5 trails up to 53.6 m long. Seventeen mounds had trails going to a Doug las fir tree (Pseudotsuga sp.). Activity at trail checkpoints varied f rom 0-171 ants per minute during the day. Ants marked on one mound wer e found on as many as 24 other mounds up to 77.9 m away. Ants were obs erved on 12 plant species and tended aphids on nine of them. Leaf clus ters on mountain snowberry (Symphoricarpos rotundifolius A. Gray) and Saskatoon serviceberry (Amelanchier alnifolia Nuttall) contained up to 1163 aphids/cluster and predaceous insect larvae. Ants also tended tr eehoppers, scale insects, mealybugs and galls on plants. Ants were see n feeding on an owl carcass, but usually scavenged dead insects. A bea r cub was observed excavating mounds. The results are compared to othe r studies of this species.