Heathland, nest on top of a small hill.
The workers from this moderately populous nest were on average slightly smaller (based on subjective eye inspection) and distinctly darker in mesosomal colouration than the typical heathland rufibarbis of northern Belgium. Darker workers seem to occur in most rufibarbis colonies here, but they usually only make up a minority of the population (<20%). In this colony, all workers had dark patches of varying sizes on the mesosoma, ranging from mostly grey with small reddish patches at the mesosomal sutures, to mostly reddish with darker patches on the top of the promesonotum and the meso- and metapleuron.
I counted setae on a sample of 20 individuals under the same microscope used to take these pictures. Because the magnification isn’t as high as would be optimal, the setae are often only visible from a certain angle and/or with a certain background. Therefore I checked each specimen from multiple angles and always used the maximum number of setae that I could distinguish with certainty from a single viewing position. Nevertheless, I expect that the attained values slightly underestimate the actual setae numbers across the sample. I’m planning to use the same methodology on some other nest samples so I can compare them.
For this nest sample of 20 individuals, the arithmetic means are 21.45 (12-29) setae on pronotum, 5.65 (0-12) on mesonotum, and 3.15 (1-5) on petiole.
The photo collages each show a single individual from multiple angles, except for the photos taken in the field which show random non-collected workers at the nest entrances.
By the look of it looks like it started by Diacamma tryingto steal Odontoponera's catch
too abundant here. I think one could use their encounter rate to tell the time
The third picture is an other individual from the same nest