Lasius fuliginosus - "Jet Ant"
The Lasius fuliginosus, often called the Jet Ant or Jet Black Ant, is a distinctive ant species known for its glossy, dark brown to black exoskeleton and a uniquely heart-shaped head. Workers typically measure between 4-6 mm, while queens are larger, ranging from 6-6.5 mm. This species constructs remarkable 'carton' nests by chewing wood and mixing it with their saliva and glandular secretions, resembling wasp or bee hives. They are also notable for their foraging behavior, forming long, visible trails, especially to trees where they tend aphids for honeydew, which is a primary food source for them.
- Difficulty: Hard
- Origin & Habitat: Europe, North Asia, parts of Siberia, and Central Asia. in Primarily found in old woodlands, scrub, pasture, and hedgerows, often nesting in cavities at the base of old trees (like oak, birch, willow, pine), rotting stumps, or sometimes under stones and in open soil..
- Colony Type: Polygyne (multiple queens), temporary parasitic (queen invades another species' nest) founding.
- Size & Growth:
- Queen: 6.0-8.0mm
- Worker: 4.0-7.0mm
- Colony: Large (tens of thousands to millions). Fast growth.
- Antkeeping:
- Temperature: Room temperature is generally suitable for Lasius fuliginosus. While specific nest temperature details aren't widely documented, maintaining a comfortable range between 20-25°C is a good starting point for most ant species. Given their natural habitat, they are adaptable to temperate conditions..
- Humidity: Humidity preferences are not explicitly detailed, but given their carton nest construction within wood, a moderate to slightly humid environment is likely beneficial to maintain the integrity of their nest material and for brood development. Aim for a consistent humidity level within the nest chambers..
- Diapause: Required. 5.0-6.0 months at Not specified.
- Nesting: This species has a strong preference for building 'carton' nests made from chewed wood and saliva. In captivity, they will require a setup that allows them to construct this material. This often means providing wood or cork inserts within an acrylic or glass formicarium. They are arboreal and lignicolous, preferring to nest in hollow trees, logs, stumps, or sometimes in walls and under stones..
- Behavior: Low (towards handler, but defensive of colony and resources) aggressiveness.
- Common Issues: Difficulty with parasitic founding in captivity, Finding suitable host species for founding queens, Maintaining carton nest integrity (if providing materials for self-construction), Humidity fluctuations impacting carton nest, Large colony size management, Providing adequate and consistent food sources.
One of the most fascinating aspects of Lasius fuliginosus is their unique colony founding strategy. These queens are temporary social parasites, meaning a newly mated queen cannot start a colony on her own. Instead, she must infiltrate an existing nest of another Lasius species, typically from the Lasius umbratus group (which includes L. umbratus, L. mixtus, L. bicornis, and others) and sometimes even Lasius niger. The queen then takes over the host colony, often by killing or ousting the original queen, and relies on the host workers to care for her initial brood. This parasitic nature makes them particularly challenging to establish in captivity, as providing suitable host workers and successfully integrating the queen is crucial.
Lasius fuliginosus is considered a 'hyperparasite' because its primary host species, like Lasius umbratus, are themselves temporary social parasites of other Lasius species (such as L. niger or L. flavus). This multi-layered parasitic relationship highlights the intricate ecological interactions within the Lasius genus. Successful adoptions of L. fuliginosus queens by host colonies have been achieved in artificial conditions, but it requires a deep understanding of their biology and careful management of the host colony.
Their distinctive 'carton' nests are a key feature. These nests, made from macerated wood hardened with mandibular gland secretions, can be quite large in the wild, sometimes reaching significant sizes within tree cavities, rotting stumps, or even structures like cellars. In an antkeeping setup, replicating this nesting material or providing an alternative that allows them to create similar structures is vital for their well-being and colony expansion. This is not a species that will thrive in a simple test tube or acrylic setup without a dedicated 'carton' section.
Foraging behavior is another notable trait. Lasius fuliginosus workers are primarily honeydew farmers, tending to aphids on trees and shrubs, and forming long, conspicuous trails to these food sources. While they occasionally take dead insects, honeydew is their staple. This dietary preference means that in captivity, a consistent supply of sugary liquids (like sugar water or honey-dew) is essential, supplemented with small protein sources. Observing their foraging trails in an outworld can be quite engaging for the antkeeper.
Colonies of Lasius fuliginosus can become very populous, with some wild colonies estimated to reach up to 1.5 to 2.0 million workers, and they are often polygyne, meaning they can have multiple queens. This potential for immense colony size means that any long-term antkeeping setup must be prepared to accommodate significant growth, requiring large nesting areas and foraging spaces. Managing such a large colony requires dedication and experience.
