Welcome to re-published posts in my Pandemic “Curious About” series, created to help us all build new connections with the plants and animals who share our Wenatchee Valley home. I feature one species at a time, but you’ll see how connected each is to other organisms in the shrub-steppe ecosystem. By sharing lots of links and ideas, I will strive to trigger new life-long learning experiences for all readers. Today’s critter is the western thatching ant.
I’m pleased to introduce you to the Western Thatching Ant (Formica obscuripes), an ant this is especially common in the Pacific Northwest from grasslands to forests. Most are black-and-red, but some are all black within the same colony. With warmer spring weather, thatching ants have emerged from their colonies and are easy to see in the Wenatchee Foothills. Their name refers to the large mound of twigs, grasses, soil, and plant parts they build on top of of their ground nest. A single colony is spread out between several mounds and worker ants are constantly at work maintaining the thatch. The large mound serves to insulate the ground nest so it maintains a uniform temperature at all times.
Kids and adults alike can visit the Critter Catalogue website to learn all about thatching ant life cycle. 10,000-40,000 individuals make up a colony and they are active during the day. Another great identification resource for ants, spiders, and insects is Bug Guide. The “BugLady’s” post about thatching ants is a quick and easy read. If you’d like help identifying an insect you find, try this Washington focused photo website. This You-Tube video of a HUGE mound in Oregon is impressive. So is this filmed-in-Washington 9 minute You-Tube video with cool music accompaniment. In the video, you can see a close up silhouette of one ant that shows you the “notch” on top of the thorax. Check out the WSU Extension Bulletin that has a nice diagram to show the thorax difference between carpenter ants and Western thatching ants.
Who eats thatching ants? Our resident northern flickers and American crows prey on thatching ants. Soon, when western kingbirds and eastern kingbirds arrive to nest and rear young in our regions, they will seek out thatching ants as an important source of protein.
What do thatching ants eat? They are omnivores and eat many kinds of insects like grasshoppers, beetles, pillbugs, and other ant species. They scavenge on dead insects. They eat plant nectar, leaves, galls, and flowers. Later in the spring they will begin “ranching” aphids (like cows). They move over-wintered aphids out of the nest and up onto to juicy “pastures” of stems of plants like lupine. By June, many of the trailside lupines will look black and upon close inspection, you can find busy ant cowboys tending their cows (aphids).
The aphids suck up sugary plant juices and then excrete “honeydew” – a rich food source of carbohydrates, water, and amino acids. The ants collect the honeydew (sort of like milking a cow??) and deliver it to the nest, to serve as food for the queen, and for developing larvae.
Check out my bibliography for more insect learning tools and field guides. Next time you head out on a trail, take along a magnifying tool so you can have an up-close and personal introduction to a neighboring thatching ant.