• Josiah Kilburn

Formica, The Crossroads Of Diversity

(This post is one of my original posts from my old blog, updated and improved with better terminology, it focuses less on taxonomy and more on captive care than most of my posts do/will. I also added two more sections about different Formica types. )


When it comes to ants, especially those of Colorado, you will have a hard time finding more diverse genus than Formica. Some nest in soil, others in rocks, a few in trees, and a couple in carefully constructed pine needle mounds. Some are scavengers, some are slavers, and some are farmers. Formica is a very diverse genus, here in colorado, there are more than 60 species, more species than any other region in the world.

Generalist (or feild) Formica species

Chances are, if you’ve been raising ants for a while and you live in Europe or North america, you have kept some form of generalist Formica species. This a relatively easy to keep and very common genus. Formica is a nearartic and subtropical genus, the lowest it ranges is Indonesia, the highest is Alaska/Canada. Most species of Formica are found in the United States. In the US, the most diverse state population is found in Colorado. They are one of the few cold resistant genuses which stays out a few weeks past the first snow. I'm classifying field or soil nesting formica as generalists, and the other types Formica fit into different category. Formica is the only genus of ants with species that build their nests entirely out of pine needles and sap. Other than these few species most do implement needles and bark into the entrance of the nest. some of these formica even inhabit deserts and desert wash habitats.


A nest of Formica cf. pallidefulva in a dried up water drainage gulch.



Arboreal (or wood nesting) Formica species

Now before you think to yourself that arboreal species only apply to canopy ants and ones living in live trees. Here is my 2 cents, arboreal is defined as related to trees or inhabiting trees, so therefore, if you find an organism nesting in a rotting log, couldn't it be defined as arboreal? Anyways, that's how I'm defining it, so arboreal Formica species typically nest in rotting logs, but a minority of them actually inhabit pine roots and lower trunks of pine trees. However most of their nests are in trees that have already fallen. The majority of arboreal Formica species can be found just below the bark of a log, but a few of them will venture deeper, most will venture deeper if wood is soft enough.



Mound nesting Formica species

Formica generally form relationships with evergreen trees in one way or another. a great example of an interesting symbiosis between the two, is the large array of "mound ants" a group of formica which build hills of needles and nest often underneath pine trees. They form multiple symbiotic relationships with the tree. Mutualism exists between the ants and the tree just by nesting nearby, not only do they capture and consume pest insects, which benefits both the tree and ants, but they also repel animals like bears and deer which could harm the tree by licking or scratching off the bark. Many people might not actually know this but parasitism is actually a symbiotic relationship as well, these ants often tend to scales and aphids on the base of the needles. They also take resin from the trees sometimes, and use this to help cleanse the ants of pathogens from the nest, usually this has little to no effect on the tree, making this commensalism, another symbiotic relationship. More often than not, queens of this species found parasitically, which is interesting because they usually have the largest colonies of formica.


Old image of a small mound nesting formica species (I mistakenly ID'd them as F. coloradoensis which doesn't exist, I likely meant F. coloradensis but this incorrect as well) The are probably Formica cf. lepida but I can't find a perfect match.



Slaving Formica (and Polyergus)

Some Formica collect the brood of other host Formica. while relatively rare most places, in Colorado, ants that slave Formica are relatively common. they are very interesting and are high maintenance species to keep as they constantly need access to brood of other Formica. There are some creative setups online. I personally don’t keep these types of Formica when I catch them because finding the correct host Formica brood sometimes takes a while. I’ll usually preserve most of my slaving Formica especially when they die. All slaving Formica are also parasitic, which makes them even more difficult to raise. But it is not impossible, it requires some more resources and creativity than most Formica, but that’s the challenge! This is a difficult species to raise in captivity, if you have a strong experience base with complicated species, and ample access to formica brood, you can probably manage this species in captivity.


Old image of parasitic Formica cf. puberula queen.



Ill update this post with more images soon!

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