Harvester Ants of California

     The state of California is one of the most diverse states in the country when it comes to ants. Some of the most iconic ants in California are harvester ants. Harvester ants are unique because one of their primary food sources is seeds. They gather seeds and bring them into their nests, which over time accumulate to create seed storages of impressive proportions. The ants then break down the seeds, and use this nutrition to feed both adult workers and developing larvae, as well as the queen. 

    In California, the two major seed-harvesting genera are Veromessor and Pogonomyrmex. The two have a lot in common, as both are avid seed harvesters. However, there are a few notable differences. Veromessor within California are often polymorphic (multiple sizes of workers), as is seen in the common desert species Veromessor pergandei. Pogonomyrmex within California are exclusively monomorphic (single worker size). Additionally, Pogonomyrmex species have convex thoraxes, while Veromessor species feature two distinct bumps on their thoraxes. 

    I personally have kept six species of harvester ants from California, two Veromessor species and four Pogonomyrmex species. They have all been a joy to keep, due to their non-stop activity, and organized nature. I recently recorded some footage of some of my personal favorite species, Veromessor pergandei and Pogonomyrmex subdentatus, which displays some of the aforementioned behavioral and morphological characteristics of the two genera.

Pogonomyrmex subdentatus

Veromessor pergandei

    In regards to care, each species of harvester ant has their own set of care requirements. Starting with Veromessor, there are two commonly found species in California, V. andrei and V. pergandei. I have started colonies from queens of both species, and they are generally quite forgiving. Before diving into the specifics, it is worth noting that none of these ants require a nectar/sugar source. They can get all the carbohydrates they need from a seed-based diet. 

    Veromessor andrei is a semi claustral species, which means the queens must be fed throughout the founding stage (the time between when a queen leaves her parent nest and when her first workers are born). I personally have founded queens of this species in test tubes, then move them into dirt-based habitats when workers arrived. During the founding process I provide the queens with enough dry foods to last them until their workers arrive, then leave them alone for at least 6 weeks. Checkups can be conducted every week or so, but disturbances at a more frequent interval may lead to stress and brood consumption in founding queens. I feed my queens a diet consisting of Kentucky bluegrass seeds, poppy seed, and crushed freeze-dried mealworms. I also supplement them with high quality fish flakes, as they are readily consumed by the protein-hungry larvae. In my experience they don't like fresh insects. I keep queens and colonies of this species in a temperature gradient, ranging from 75F on the coolest end to 80-85F at the warmest end. When kept at such temperatures, you can expect to see first workers within 6-8 weeks. Once the queen gets workers, I continue feeding the same diet and keep them at the same temperature, though the quantity of food provided should be increased proportionally to colony size. Upon arrival of workers, I typically keep my colonies into dirt setups as I have observed my colonies produce best in them. As the colony gets larger, I simply transfer them into larger dirt based-setups.

    Veromessor pergandei is a fully-claustral species, which means that the queens will not need to be fed until their first workers arrive. I have had success keeping these ants in a wide variety of setups, including test tubes, dirt habitats, and plaster-based formicaria. During founding I typically use test tubes or dirt nests, and limit disturbances/checkups to once every week or so to prevent excess stress. I feed my ants the same diet as Veromessor andrei. The only difference is that this species readily accepts freshly killed feeder insects, whereas Veromessor andrei do not. I personally found the queens in test tube setups, with additional seeds to supplement larval development. While this is not required as the queens are fully claustral, I prefer doing this to increase the amount of energy and food available to the fledgling colony. Once the queen gets her first workers, they can be moved to a plaster formicarium, a dirt formicarium, or kept in their test tube and fed accordingly. When the colony outgrows their setup, a larger one of a similar fashion can be provided. Their temperature requirements are almost identical to that of V. andrei, however they are less heat tolerant in my experience, and temperatures should not exceed 85F.

    The second genus of harvester ants in California, Pogonomyrmex, is slightly more demanding in terms of care. In terms of temperature, I keep all my Pogonomyrmex colonies at a gradient of approximatley 78F to as high as 90F, as I have observed such high temperatures aid brood development. It is also worth noting that like Veromessor, Pogonomyrmex do not need additional sugar or nectar sources, as a grain-based diet provides enough carbohydrates for them to flourish.

    Pogonomyrmex utilize two different approaches to founding. Fully claustral species (Pogonomyrmex rugosus, P. tenuispinus, etc.) do not forage for food during the founding process, and raise their first batch of workers without any food. Semi-claustral species (Pogonomyrmex subdentatus, P. californicus, P. subnitidus, etc.) forage for food during the founding process. 

    I personally provide both fully and semi claustral Pogonomyrmex species with food during the founding process, as in my experience, even fully claustral queens will accept food if provided to them. Because of this, my care for them during founding is identical. 

    During founding I use a tube/outworld combination or a dirt setup, and provide enough seeds and crushed freeze-dried insects to last the queen throughout the founding process. After this, I limit checkups as much as possible, only disturbing them to rehydrate their setups if they are in dirt After the six week mark, I conduct weekly or bi-weekly checkups to check for first workers. Upon arrival of first workers, the first fresh insect meal can be fed. Some species are more receptive to fresh insects than others, so it is not cause for concern if a colony is not receptive to them. I simply give all my Pogonomyrmex colonies such meals to ensure that if the need for additional protein arises, the colony will have some.

    For all Pogonomyrmex species, the ideal diet is quite consistent. I feed all my Pogonomyrmex the same diet as the aforementioned diet for Veromessor pergandei. They need grains and insects to thrive. I use the same mix as with V. pergandei, containing Kentucky bluegrass, poppy seeds, and crushed freeze dried insects. Additionally, I supplement them with high quality fish flakes and freshly killed feeder insects. The contents of the diet remain the same throughout the colony's lifetime, the only difference being that during founding I refrain from feeding insects as there are no workers present to aid in breaking them down.

    I personally enjoy observing and keeping all of California's harvester ants. They behave in a similar fashion, being active, and coordinated foragers. However, each species has their own little unique traits which makes them interesting to keep. If you are looking into ant keeping, I would definitely recommend giving harvester ants a shot!