Western thatching ant

Definition

A large, mound-building ant species (Formica obscuripes) native to western North America, notable for constructing conspicuous above-ground nests roofed with thatch—interwoven fragments of grass, pine needles, and other plant debris. Colonies are populous, often exceeding 30,000–40,000 workers, and function as ecologically important predators and tenders of sap-sucking Hemiptera.

Etymology

Western: geographic range in western North America; thatching: from the distinctive roofed nest structure resembling a thatched roof.

Example

In montane meadows of the Rocky Mountains, Western thatching ant mounds may reach 1 m in height and serve as thermal refugia, with workers aggressively defending the territory and harvesting honeydew from tended aphid colonies on nearby vegetation.

Synonyms

• Formica obscuripes

Related Terms

• Formica
• thatch
• mound-building ant
• honeydew
• Trophobiosis
• polycalic
• Formicidae

Usage Notes

The common name refers specifically to F. obscuripes; other Formica species (e.g., F. rufa group in Eurasia) are also called thatching ants, but 'Western' restricts usage to this Nearctic species. Sometimes confused with Allegheny mound ant (F. exsectoides) in overlapping ranges, but the thatched roof of plant material distinguishes F. obscuripes from the bare soil mounds of F. exsectoides.