ALARM-DEFENCE SYSTEM OF ANT LASIUS ALIENUS

The principal volatile products of the formicine ant Lasius alienus were identified, their glandular sources located in part, and their functions analysed. The more abundant substances in the C9-C10 range were shown to be alarm substances, with behavioral threshold concentrations estimated to vary in order of magnitude from 107 to 1011 molecules/cm3. Undecane, the principal component, was shown to be more effective as an alarm substance for L. alienus, whose estimated response threshold is 107 to 1010 molecules/cm3, than for the relazed species Acanthomyops claviger, whose estimated threshold is 1010 to 1012 molecules/cm3. L. alienus appears to depend less in its defence strategy on orientation toward points of disturbances and defensive chemical sprays, and more on 'early warning' and evacuation, than does A. claviger. © 1969.