● NW of Mattawa [Grant Co], WA USA [el. 152 m / 500 ft] view location in Google Maps »
● 5/9/10 10:14AM sunny, air temp: 16°C / 61°F
[IMAGE 1 of 4] The seeds of western tansy-mustard (Descurainia sp.) are apparently a very important source of food for the Pogonomyrmex salinus ants of central Washington state. This series of four images was captured in the space of less than one minute - as a determined worker removed a relatively huge seed-pod from a living plant near her nest. Using her legs and gaster (large abdominal body part) to maximize leverage, she can be seen cutting through the stem, just below the seed-pod (1st and 2nd images). Suddenly, the pod is cut free, and the ant climbs out to the end of a seed-pod below, with cargo firmly held in her mandibles (3rd and 4th images). Two seconds after the last image, she dropped to the ground (from a height of about 25 cm / 10 inches) and ran at full speed to the nest, disappearing into the entrance with her prize.
Descurainia (tansy-mustard) species thrive in dry (and often disturbed) soils, and are quite abundant in many areas where Pogos live. Nest middens are often full of empty Descurainia seed pods. We have observed and imaged P.salinus workers interacting with these plants in several locations in Washington state. These interactions encompass a range of behaviors, including the foraging of seeds/seed pods, removal of empty seed pods from nests, and the removal of entire plants from nest mounds and adjacent areas. Pogonomyrmex salinus has also been observed to collect the seeds/seed pods of various Descurainia species in Oregon and Idaho, and one study indicates that in central Oregon, Descurainia pinnata (western tansy-mustard) is one of the 5 most frequently collected seeds by P. salinus. The others were: Bromus tectorum, Phacelia linearis, Hordeum jubatum, and Sisymbrium altissimum.
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex owyheei in Southest Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982
·Willard, J.R. & H.H. Crowell. 1965. Biological Activities of the Harvester Ant, Pogonomyrmex owyheei, in Central Oregon. Journal of Economic Entomology Vol.58, No.3 - Pogolumina - Pogonomyrmex Harvester Ants of North America
Images of Pogonomyrmex salinus - at various locations in Nevada, Oregon, and Washington states, USA. Scroll down PAST BOTTOM OF PAGE for complete image description, and CLICK large image to make it even LARGER...
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