Chaff from P. salinus nest in central Washington state.

Chaff consists of the discarded seeds and other plant matter taken from the nest interior, and generally deposited on the edges of the mound structure. This area is sometimes referred to as the 'midden', or 'kitchen midden'.

This material can include the inedible remnants of previously harvested seed pods and grass spikelets, and seeds that have sprouted. Potential food items that have otherwise been damaged by water or contaminated by mold or fungus, may also be discarded, or left out for a period to dry in the sun [1].

The Florida harvester (Pogonomyrmex badius) places bits of charcoal in the midden surrounding its nests. One theory suggests that sometimes this debris, possibly impregnated with a chemical substance by the ants, may serve as a boundary marker - discouraging ants of other species from approaching the nest mound [2].

Ants that have died within the nest are sometimes placed here (in the midden) as well. [IMAGE: discarded plant material (chaff) from the midden of a P. salinus nest in central WA state - dominated by seed pods of Descurainia sp. (tansy- mustard) and parts of grasses - scale in centimeters/millimeters] [scroll down for additional notes/references]

ADDITIONAL NOTES/REFERENCES:

[1]
·McCook, H.C. 1880. The Natural History of the Agricultural Ant of Texas. A Monograph of the Habits, Architecture, and Structure of Pogonomyrmex barbatus. Philadelphia: J.B. Lippincott & Co. 1880
·Taber, S.W. 1998. The World of the Harvester Ants. College Station, TX, Texas A&M University Press
·Wheeler, W.M. 1910. Ants: Their Structure, Development and Behavior. New York, Columbia University Press

[2]
·Gordon, D.M. 1984. The Harvester Ant (Pogonomyrmex badius) Midden: Refuse or Boundary? Ecol. Entomol. 9: 403-412