Formica obscuripes

Formica obscuripes
F. obscuripes worker
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Genus: Formica
Species: F. obscuripes
Binomial name
Formica obscuripes
Forel, 1886

Formica obscuripes (the western thatching ant) is a species of ant in the family Formicidae. It is native to North America. It produces large mounds covered by small pieces of plant material.[1] The number of adult workers per colony may be as high as 40,000.[2] F. obscuripes feeds upon a number of insect species, consumes nectar from homopterous insects they tend, and occasionally eats plant tissue.[1] In the Blue Mountains of Oregon, F. obscuripes has demonstrated the capacity for polydomy. A supercolony in a four-hectare study area near Lehman Hot Springs consisted of 210 active nests with an estimated population in excess of 56 million ants.[3]

Nests

F. obscuripes mound (left), close-up of a mound (center), F. obscuripes on mound (right)

F. obscuripes produce large dome-shaped mounds composed of varying material. The composition of the nest is based upon the immediate plant environment and is commonly referred to as "thatch". The size of these mounds is highly variable and dependent on the age and health of the colony. The height of the average mound ranges from 1 inch (1.5cm) to 18 inches (45.7cm), although nests of larger heights are not uncommon. Nests can extend up to 4 feet (1.2 meters) into the ground. The mounds are typically constructed in a open areas devoid of cover and are often formed around a structure. The condition of the thatched mound is in a constant state of change due to activities by the ants and environmental factors.[4] When a colony possesses a suitable amount of adult workers, the ants proceed to chew off the bark at the base of plants growing on or nearby the mound. Formic acid is ejected (sprayed) into the open layer eventually felling the plant. [5]

References

  1. 1 2 Heikkinen, M. W. (1999). "Negative effects of the western thatching ant (Formica obscuripes) on spiders (Araneae) inhabiting big sagebrush (Artemisia tridentata)". Great Basin Naturalist 59 (4): 380–383.
  2. ↑ Capinera, J. L. (2008). Encyclopedia of Entomology, Volume 3. Springer. p. 4215. ISBN 978-1-4020-6242-1.
  3. ↑ McIver, J.; Torgersen, T.; Cimon, N. (1997). "A supercolony of the thatch ant Formica obscuripes Forel (Hymenoptera:Formicidae) from the Blue Mountains of Oregon". Northwest Science 71 (1): 18–29.
  4. ↑ Weber, N (1935). "The Biology of the Thatching Ant, Formica rufa obscuripes Forel, in North Dakota. Ecological Monographs," (PDF).
  5. ↑ Cole, S.C. Jr. (1932). "The Thatching Ant, Formica obscuripes Forel Psyche Volume 39 (1932), Issue 1-2," (PDF).

External links


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