This semester in the Bee Lab I am working on the Ant Wars Project, focused on the interactions between native harvester ants (Pogonomyrmex californicus) and invasive Argentine ants (Linepithema humile). Harvester ants are a keystone species in California which are known to be threatened by Argentine ant invasion. They are able to alter soil characteristics since their nests are much deeper than those of Argentine ants. Ant diversity is also very important for the overall health of ecosystems since ants can often serve different ecological purposes.
Specifically we are analyzing the foraging habits of harvester ants to see how they are impacted by the presence of Argentine ants. We do this by monitoring their nests and seeing when they exit or enter and open/close their nests across a couple thousand (yes thousand) videos—taken in the fall semester.
During one such watchthrough I saw a weird looking ant. It was wider, black instead of red, and had a totally different body shape. On second thought… maybe it wasn’t an ant?
Unsurprisingly harvester ants live interesting lives, surrounded by other flora and fauna in the Bernard field station and one of these was a round black beetle. The next thing shocked me. It waddled right into the harvester ant entrance!
Clip of Beetle Entering Nest (10/30/2026) [3]
I had never seen something like this happen. Harvester ants are known for their painful stings and they are pretty large as far as ants go. Even more surprisingly the ants ignored it completely. Did this adventurous beetle ever make it out? In the five minute video it is not seen exiting and in the next video an hour later there is no beetle present, leaving its fate undetermined.
This had me wondering. What type of beetle was this? Was this just a mistake it made wandering into a harvester ant nest or was it purposeful? Was it some sort of symbiotic relationship?
Species that have a symbiotic relationship with ants specifically are called myrmecophiles.
Well, how does one evolve to live alongside ants? What traits do myrmecophiles need to live alongside ants?
One article I found used a 99 million year old amber fossil of a beetle (Promyrmister kistneri) to show how haeteriine beetles evolved alongside ants becoming more social. It was encased in amber and found in a mine in Myanmar. This beetle shared some traits of modern clown beetles such as their legs and glands at their legs to produce chemicals to trick ants.
[4]: Image of Promyrmister kistneri in amber.
The relationship between ants and beetles is one of the oldest examples of a symbiotic relationship. Modern myrmecophiles will become extinct without an ant host since they are so adapted to living with ants.
Co-evolution is something we have been discussing in Bio 46 (one of the core classes at Harvey Mudd) in the context of HIV. The evolutionary tree for HIV has a similar shape to that of primates. Using this information you can map the likely host transfers between species. Similarly Haeteriine clown beetles sometimes needed to jump to different ant species in order to survive.
Now, one might ask if there are already known myrmecophilous species that interact with harvester ants (P. californicus).
Not exactly our specific species, but one study by William MacKay excavated Pogonomyrmex montanus, P. subnitidus, and P. rugosus. These are all species in southern California and related to Pogonomyrmex californicus. Their findings were organized by host species and depth found, as well as other identifiers.
Since this beetle was seen entering the nest we can narrow our search to beetles found near the surface or 10 cm deep in the nest.
The Anepsius delicatulus had the most similar coloring to the beetle I saw, but it seems a bit longer than the beetle in the video.
The most frequently spotted beetle on the surface next to Pogonomyrmex ant colonies was Notibius puberulus and is part of the family Tenebrionidae which comprises over 20,000 species! They are scavengers and most of their diet consists of plant matter. Notibius puberulus is observed to have back legs, or tibiae that are shaped like shovels, likely for digging.
Another possible clue is a second beetle I spotted digging in the corner of the video:
Clip of Beetle Digging Near Nest(10/30/2026)[7]
Since the quality of the video is relatively low, we cannot correctly identify what beetle it is, but we can note down some observations about its appearance and its habits.
There are a couple of ways we could identify beetles near the harvester ant colonies we study. One is to repeat the method used in the study where parts of Pogonomyrmex colonies were excavated. Unfortunately this would likely disturb the ants and might lead to a sudden shift in foraging habits or nest entrance location, which could leave them open to Argentine ant raids.
Another idea is to try and catch one of these beetles, although it would be difficult to try and catch a beetle near one of the colony entrances. They might be able to dig inside the ground and again, harvester ants have painful stings. Trying to rummage around their nest entrance catching a beetle might not be the best idea.
The best method of observing beetle species might just be to add them to our regular observations of harvester ants. It will not be possible to correctly identify the beetle through video footage due to the poor quality.
The videos we took are almost daily, so in our observations of the foraging habits of harvester ant behavior we were able to record the presence of some beetles. We could also document the frequency of the beetles and specific colonies where they are observed.
What working on the Ant Wars Project taught me is that in observing small events you can build up a bigger picture of a larger ecological phenomenon. Perhaps the appearance of these beetles will show other ways harvester ants impact the environment and give us more reason to protect this species.
Future Reading:
Dajose, Lori . “These Beetles Have Successfully Freeloaded for 100 Million Years.” California Institute of Technology, 2019, www.caltech.edu/about/news/these-beetles-have-successfully-freeloaded-100-million-years. Accessed 9 Mar. 2026.
MacKay, William P. “Beetles Associated with the Harvester Ants, Pogonomyrmex Montanus, P. Subnitidus and P. Rugosus (Hymenoptera: Formicidae).” The Coleopterists Bulletin, vol. 37, no. 3, 1983, pp. 239–46. JSTOR, http://www.jstor.org/stable/4008025. Accessed 9 Mar. 2026.
Margarethe Brummermann. “Darkling Beetles (Tenebrionidae) in the Dunes of Western Arizona.” Blogspot.com, 2019,
arizonabeetlesbugsbirdsandmore.blogspot.com/2011/03/darkling-beetles-tenebrionidae-in-dunes.html. Accessed 9 Mar. 2026.
Entomology Today. “Harvester Ant Nest Rims Boost Native, Nonnative Plants Alike.” Entomology Today, 25 Jan. 2024,
Media Credits:
[1]: Photo by Alex Wild. https://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Pogonomyrmex/i-PgrMrXH?from=search-page&searchText=Pogonomyrmex+californicus
[2]: Photo by Alex Wild. https://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Linepithema/i-tct8wsd/A
[3]: Video taken by Ant Lab in the Bernard Field Station
https://drive.google.com/file/d/1yMfBrMcV1nNmE5fKeKMN8tkf7Jh9VIp8/view?usp=sharing
[4]: Photo from Zhou et al. https://pmc.ncbi.nlm.nih.gov/articles/PMC6467565/figure/fig1/
[5]: Photo from Jerry Wilson. https://www.bugguide.net/node/view/1537001
[6]: Photo from Margarethe Brummermann.
[7]: Video taken by Ant Lab in the Bernard Field Station
https://drive.google.com/file/d/1yMfBrMcV1nNmE5fKeKMN8tkf7Jh9VIp8/view?usp=sharing
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