Anthill Ecology Formica obscuripes
Anthill Ecology Formica obscuripes
Anthill Ecology Formica obscuripes
Anthill Ecology Formica obscuripes
Anthill Ecology Formica obscuripes
Anthill Ecology Formica obscuripes

Anthill Ecology Formica obscuripes

Among the many ant species in northern Washington State are these thatching ants, Formica obscuripes. In some cases, the activity of the ants causes plants to flourish in a ring around the hill. This effect seems to work with different species of plants, like these hills ringed in grass and a flowering herb.

I noticed that the ants at the hill in image 1 congregated in a crescent-shaped area defined by the shadow of the vegetation.

In the video (6), note a morph with a smaller, darker head emerging from the hole near the end. A similar morph also appears in this image. These morphs are not separate castes as in some other ant species.

The effects on plants near ant hills may arise from several factors (source), including seed dispersal by the ants, a process called myrmecochory (1 | 2 | 3).

Thanks to James C. Trager for the species ID on bugguide.net.