The Feeding Habits of the Wood-Ant, Formica rufa (Hymenoptera: Formicidae), in Limestone Woodland in North-West England

Abstract

SUMMARY (1) Food habits of Formica rufa L. in a limestone woodland in north Lancashire are studied. Use is made of a semi-automatic collecting device which solves some of the problems inherent in manual sampling. (2) The main food items are shown to be aphids (mainly Drepanosiphum platanoides Schr.), Diptera (mainly Bibionidae), Lepidoptera larvae (mainly Operophtera brumata L.) and honeydew. (3) Aphids, Lepidoptera larvae and honeydew are brought in in greatest quantities in spring and early summer, Diptera throughout the year. Differences in food income at two study sites are discussed in relation to differences between the two sites. (4) Many ants are shown to be involved in the collection of building material or are apparently unladen. (5) Dry weight studies show honeydew to be the most important food in these terms. (6) Honeydew was also found to be the most important food in terms of energy content. Up to 15 200 kJ/5 min of honeydew are carried in on a single trail. The maximum intake of solid food on the same trail was 13 287 kJ/5 min. (7) Formica rufa is shown to utilize particular species of tree at different times of year. Sycamore is important in the early season with scots pine and oak increasing in importance in summer and autumn. This is related to the food being obtained from these species. (8) The present results are discussed in relation to previous data on wood-ant feeding habits and its more general applications are discussed in terms of work done on food selection in birds. The importance of assessing the impact of large ant colonies on the ecosystem via studies of their food income, etc. is stressed.