Formica obscuripes

Western Thatching Ant
Formica obscuripes

 

Identification:

Western Thatching Ant Formica obscuripes workers on 5' round nest
Western Thatching Ant Formica obscuripes workers on 5′ round nest. Nest is about 10 inches high. July 01, 2010 Celista, B.C.
Western Thatching Ant Formica obscuripes worker on leaf
Western Thatching Ant Formica obscuripes worker. July 01, 2010 Celista, B.C.
Western Thatching Ant Formica obscuripes workers beetle flipping
Western Thatching Ant Formica obscuripes workers engaged in beetle flipping. No one knows why they do this. June 21, 2010 Celista, B.C.
Western Thatching Ant Formica obscuripes worker
Western Thatching Ant Formica obscuripes worker in nest. July 01, 2010 Celista, B.C.

Workers: Head and thorax light red, smaller workers spotted with brown. Legs and horn (petiole) are reddish-brown. Abdomen deep brown or blackish, covered with slightly long and dense, gray hair. Eyes hairy.

Size: Worker 3.8 to 8 mm long.

Habitat: Prairies, grassy meadows, pine forest edges.

Food: Other insects found dead or alive are carried back to the nest. Also honeydew from aphids and treehoppers. Travel high up in trees and are an important predator of the Western Spruce Budworm and other larvae. Also engage in ‘beetle flipping’, turning beetles on their backs before carrying them to the nest as food.

Flight Time: Late June to early July. Morning flights.

Life Cycle: Nests are found in open areas; large mounds covered by small pieces of plant material to help regulate temperature in the nest. Tunnels are deep.  Colonies are large and can be over 35,000. Newly mated queens will try to take over another Formica species nest, killing or driving off the old queen. The old workers continue to feed the new ‘foreign’ queen and her offspring until they die off, and the nest becomes entirely Formica obscuripes.  Apparently this species takes in guests – Formicoxenus hirticornis.

Synonyms: Forel 1886
Formica aggerans, Formica melanotica


References:
Bulletin of the Museum of Comparative Zoology, 1953. Vol. 53, #10, pg. 433 by Wheeler

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