Work efficiency in heterospecific ant groups composed of hosts and their labour parasites

Abstract

1. 1. The work efficiency of sand excavation in heterospecific ant groups was tested with two dulotic species, Polyergus samurai Yano ( Po), and Formica sanguinea var. fusciceps Emery ( Fs), in various combinations with their common host species, Formica fusca japonica Motschulsky ( Ff). 2. 2. Samurai never participated in the work, and effected the activities of fusca neither positively nor negatively. Although excavating behaviour seldom differed qualitatively between sanguinea and fusca, quantitative differences appeared. Sanguinea was far less efficient than in fusca individual output, in number of élites and in working procedure. 3. 3. Throughout the group sizes tested, individual efficiency seldom exceeded the level attained by single workers and generally declined as group size increased. 4. 4. The decrease of active participants or élites, was indicated as an important cause of inefficiency. The group output regressed linearly on the corrected number of élites. 5. 5. Qualitative analyses were undertaken as to the patterns of working, and the relation of such patterns to the outputs and to species-specificity was considered. 6. 6. The results were briefly discussed from both comparative and from general points of view.