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[Vol. 88 
staining was Azan (Heidenhain). The SEM pictures were taken with 
an AMR 1000 A scanning electron microscope. 
Additional methodological details will be given with the descrip- 
tion of the individual experiments. 
Results: 
As demonstrated by Carlin (1982) most of the foraging in O. 
versicolor is conducted by the minor and medium worker castes; the 
majors function primarily or entirely as a defense caste, for which 
they have unique modifications in the form of the mandibles. 
Although workers of O. versicolor seem to forage individually, our 
observations in the laboratory indicate that some sort of social 
facilitation might be involved in stimulating foraging activity in the 
colony. 
Often not more than 1-3 workers roamed the foraging arena. But 
when suddently 30-50 flightless Drosophila flies were released into 
the arena, and the first one or two foragers had returned with 
captured prey to the nest, the number of workers leaving the nest 
tube and venturing into the foraging arena increased markedly. We 
did not, however, observe the foragers performing any motor 
display inside the nest, which might have stimulated the nestmates. 
Fig. 1. Part of the colony of Orectognathus versicolor, the three worker castes 
(minors, medias, majors), males, and different developmental stages. 
