Formica exsecta - "Narrow-headed Ant"
Formica exsecta, often called the narrow-headed ant or excised wood ant, is a fascinating ant species found across Western Europe and Asia. They are recognized by their bicolored appearance, typically with a dark brown gaster and a reddish body that may have varying amounts of dark coloration on the head and mesosoma. A key distinguishing feature is their deeply excised (concave) head, particularly noticeable in larger workers. Unlike some 'true' wood ants, F. exsecta builds smaller mound nests, usually about the size of half a football, using finer plant fragments like pieces of herbs, grasses, leaves, and lichen. These active and aggressive ants are known for their vigorous biting when disturbed.
- Difficulty: Hard
- Origin & Habitat: Europe, Asia in Open woodland, moorland, rough pasture, heathland, woodland rides and clearings, roadside verges, subalpine and boreomontane pastures, semidry to xerothermous grasslands, dryer spots of bogs and fens..
- Colony Type: Monogyne or Polygyne, often forming supercolonies, temporary parasitic (on formica lemani, formica fusca, or formica cunicularia) or colony fission. founding.
- Size & Growth:
- Queen: 7.5-9.5mm
- Worker: 4.5-7.5mm
- Colony: Large (tens of thousands) to Supercolony (hundreds of thousands/millions). Fast, especially in polygynous colonies. growth.
- Antkeeping:
- Temperature: Maintain a temperature range of 20-28°C for optimal activity and brood development. Consistent temperatures are beneficial, but some keepers opt for a slight nighttime drop to simulate natural conditions..
- Humidity: These ants prefer a medium humidity level, around 40-60%. It's crucial to provide a moist, but not wet, environment, especially for larger colonies..
- Diapause: Required. 3-5 months at 5-10°C.
- Nesting: In the wild, they construct mound nests from fine plant fragments, often around a grass tussock or supportive structure, with a significant amount of soil. In captivity, nests that allow for depth and humidity gradients, such as those with a good substrate layer, are preferred. Artificial nests should be designed to maintain consistent moisture..
- Behavior: High (towards handler, food, or other ants) aggressiveness.
- Common Issues: Mold in nest, Colony stalling (if host workers/brood are not adequately provided for parasitic founding), Humidity fluctuations, Overfeeding leading to waste, Queen stress (especially during founding phase), Lack of suitable host species for founding.
Formica exsecta is a temporary social parasite, meaning new queens cannot found colonies independently. Instead, they must infiltrate an existing host colony, typically of a Serviformica species like Formica fusca, Formica lemani, or Formica cunicularia. The queen will enter the host nest and, over time, her brood will be raised by the host workers. Eventually, the host workers will die off, leaving a colony consisting entirely of F. exsecta offspring. This founding method is crucial to understand for successful antkeeping of this species, requiring keepers to provide host workers or brood for a newly caught queen.
This species is known for forming supercolonies and polydomous (multi-nest) systems, especially in their polygynous form where there are multiple queens. These networks can be incredibly vast, with some documented supercolonies spreading over many hectares and containing millions of workers across hundreds or thousands of nests. This complex social structure suggests that even though individual nests might be smaller, the overall colony can be immense and interconnected. For antkeepers, this means that even a single founding queen could eventually lead to a truly massive colony requiring significant space and resources.
Formica exsecta workers are generally active and aggressive, especially when their nest is disturbed. They will swarm out and bite vigorously, exhibiting territorial behavior. This aggressive nature also extends to interactions with non-nestmates; they can be quite hostile towards other ant species or even foreign F. exsecta from different colonies, particularly in spring. Therefore, when handling or performing maintenance on their setup, antkeepers should exercise caution and be mindful of their defensive tendencies. They are also known to tend aphids for honeydew, a vital food source, and are predaceous.
Interestingly, Formica exsecta can exist in two distinct social forms: monogyne (single queen) or polygyne (multiple queens). The prevalence of one form over the other often depends on the specific population and resource availability. Polygynous colonies, with their numerous queens, tend to have faster growth rates and can achieve much larger sizes, often extending their colonies through nest splitting. This plasticity in colony structure can influence how a colony develops and expands in captivity. While monogynous colonies are more prone to inbreeding and shorter queen lifespans, polygynous ones are more adept at adapting sex allocation based on resources.
Humidity and temperature management are critical for Formica species. While they can regulate their nest environment in the wild by tunneling deep, in a captive setup, the keeper must provide stable conditions. A medium humidity of 40-60% is ideal, ensuring the nest is moist but not waterlogged. For temperature, a consistent 20-28°C is good, as it promotes faster brood development and worker activity. Providing a heat gradient can allow the ants to choose their preferred temperature. Avoid keeping them in overly cold, air-conditioned rooms, as this will significantly slow down their colony growth.
Frequently Asked Questions
What kind of enclosure is best for a *Formica exsecta* colony?
For newly caught Formica exsecta queens, a simple test tube setup is ideal for the initial parasitic founding phase. Once the colony has a decent number of workers, you'll want to transition them to a larger formicarium. Given their tendency to build mound nests in the wild, setups that allow for a good substrate layer and humidity control, such as plaster or Ytong nests, are often suitable for larger colonies. Just be prepared for their growth-these colonies can get massive!
How do I start a *Formica exsecta* colony since they are parasitic?
Starting a Formica exsecta colony is different from many other species because they are temporary social parasites. This means a queen needs host workers or brood, typically from Serviformica species like Formica fusca or Formica lemani. The queen will invade a host nest, and the host workers will raise her first brood. Without host workers or brood, the queen cannot successfully found a colony on her own. Many keepers will introduce a newly caught queen to a small group of callow (young, light-colored) Serviformica workers or pupae.
Are *Formica exsecta* aggressive?
Yes, Formica exsecta are quite aggressive ants! When their nest is disturbed, workers will quickly swarm out and bite vigorously. They can also be aggressive towards other ant species and even non-nestmate F. exsecta colonies, especially in the spring when resources might be scarcer. Always exercise caution and use appropriate tools when handling them or performing maintenance on their setup.
What do *Formica exsecta* eat?
Formica exsecta are omnivorous. In the wild, they primarily feed on honeydew produced by aphids, acting as 'shepherds' to secure this sugary food source. They are also predaceous, meaning they will hunt and scavenge for insects. In captivity, a balanced diet of sugary foods (like sugar water, honey, or fruit) and protein sources (such as feeder insects like crickets, roaches, or mealworms) is essential for their health and colony growth.
Do *Formica exsecta* need to hibernate?
Yes, Formica exsecta definitely require a diapause period, which is their equivalent of hibernation. This is crucial for the long-term health and development of the colony. Typically, a diapause of 3 to 5 months at temperatures between 5-10°C is recommended. Some keepers prefer to lower the temperature gradually as winter approaches, mimicking natural conditions.
How big can a *Formica exsecta* colony get?
Formica exsecta colonies can grow to be quite large, ranging from tens of thousands of workers to even supercolonies with hundreds of thousands or millions of individuals spread across multiple interconnected nests in the wild. If you're keeping a polygynous queen (or queens), be prepared for rapid growth and a potentially enormous colony that will need substantial space and resources as it matures.
What are common mistakes to avoid when keeping *Formica exsecta*?
One of the biggest pitfalls is not providing the necessary host workers or brood for a newly caught parasitic queen. Another common mistake is moving a small, newly founded colony into a large formicarium too early, which can stress them out and lead to failure. Humidity fluctuations, overfeeding (which can lead to mold), and keeping them in overly cold environments that slow down their development are also things to watch out for. Make sure their outworld isn't overly complicated, as this can encourage ants to move out of the nest and hide.
What kind of humidity do *Formica exsecta* need?
Formica exsecta prefer a medium humidity level, ideally between 40-60%. It's important to provide a moist, but not soaking wet, environment within their nest. For test tube setups, ensure the water reservoir is well-maintained. For larger formicaria, consider designs that allow for humidity gradients so the ants can choose their preferred moisture levels.
What is the typical temperature range for *Formica exsecta*?
For optimal activity and brood development, Formica exsecta thrive in temperatures between 20-28°C. While some keepers maintain a consistent temperature, providing a slight night-time temperature drop can mimic their natural environment. Avoid keeping them in cold, air-conditioned rooms, as this will significantly slow down their growth rate.
Can *Formica exsecta* queens be kept together (pleometrosis)?
Yes, Formica exsecta can be polygynous, meaning they can have multiple queens in a single colony. In fact, polygynous colonies are often larger and grow faster. This means that, in some cases, multiple queens can be kept together, especially if they are from the same colony or if the colony is large enough to accept additional queens. Unrelated queens can sometimes be accepted into existing colonies, though their reproductive success might be lower.
How do *Formica exsecta* build their nests?
In the wild, Formica exsecta construct distinctive mound nests. These mounds are typically built from fine plant fragments like bits of leaves, grass, and lichen, often incorporating a significant amount of soil. They're usually found in open or lightly shaded areas and can be quite numerous within a supercolony network. For captive setups, this suggests providing a suitable substrate for them to dig into or a nest design that simulates these mound-building conditions.
Are *Formica exsecta* native to my region (UK/Europe)?
Formica exsecta is found across Western Europe to Asia. In the UK, their populations are quite disjunct and scattered, primarily in heathland locations in South West England and the central Scottish Highlands. They are a species of conservation concern in the UK. Always check local regulations regarding collecting and keeping native ant species.
