Formica fusca

Silky Ant
Formica fusca


The Silky Ant Formica fusca male
The Silky Ant Formica fusca winged male July 03, 2006 Wheatley, Ontario.
Silky Ant Formica fusca wingless queen
The Silky Ant Formica fusca wingless queen July 07, 2006 Wheatley, Ontario.

Identification: Silky Ant – introduced from Europe. Formica fusca is a dark-bodied species.
Workers have slender black bodies with whitish hairs on top of head, thorax and abdomen. Eyes are hairless. Antenna slender, the base (scape) is red, slightly wider at tip. Antenna segments 1 and 2 also red. Large eyes. Mandibles red, with 8 teeth. Thorax narrow. Abdomen small, whitish hairs longer with a frosted (pruinose) appearance. Legs slender, red to brownish-red. Workers are extremely timid, and subject to enslavement by other species of Formica.
Queen is black. Thorax wider than the head. Wings long, nearly colorless, stigma brown. Abdomen very smooth and shining, less hairs than worker abdomen.
Male is black, slender. Head wide across top, lower face very narrow. Eyes large, hairless. Antenna base (scape) dark brown. Mandibles narrow, pointed and toothed. Wings slightly more tinted than female. Legs yellow, feet black.  Abdomen more brownish, very shiny, long and narrow, without hair. Abdomen tip yellow.

Size: Worker 4 to 6.5 mm. Male 8 to 10 mm. Queen 7 to 10 mm.

Flight Time: July to August.

Habitat: Uncultivated land, nesting under stones and in tree stumps under loose bark.

Food: Feed on small insects, aphid honeydew and flower nectar.

Life Cycle: Nests are usually small 500 to 2,000 workers. Colonies stop producing eggs in late summer, and only adults over-winter in the nest. Winged males and females are not produced until the colony is 3 years old. The winged ants mate on the ground and the newly mated queens start a new nest, feeding their first brood alone.  Colonies can last 10 or more years.

F. fusca group ants are often the hosts of socially parasitic ants, including Polyergus and Formica slave-raiders, and the Little Black Ant Monomorium minimum. To counter these attacks, the Silky Ant has workers who monitor the larva for foreigners, and will remove them from the nest.

Comments: Essex County – not listed; listed for Ontario per NHIC (Natural Heritage Information Centre). Wheeler found it in Guelph. Also in Michigan.

Synonyms: Linnaeus 1758
Formica fusca var. glacialis

References: Wheeler, G. and J. 1986 Ants of Nevada. Natural History Museum of Los Angeles Co.