Polyrhachis glabrinota

Polyrhachis glabrinota

Polyrhachis glabrinota is a medium-sized arboreal ant endemic to northern Australia, specifically the Cape York Peninsula region. Workers measure 9.8-12mm and feature the characteristic spines on their shoulders (humeral spines) typical of the Myrmhopla subgenus. They have a distinctive bicolored appearance with a black head and mesosoma, while the propodeum and petiole are noticeably lighter, either reddish-brown or pale depending on the specimen. Their pronotum is notably smooth and polished with short, sparse hairs, which helps distinguish them from the similar-looking P. bubastes from New Guinea. Queens are larger at 11.3-13mm and share the same polished appearance. These ants are primarily arboreal, building nests between leaves in the lower canopy around 2-3 meters above ground, and several colonies have been found nesting inside bamboo stems ^[1][2].

What makes P. glabrinota stand out is their use of silk to bind leaves together into protective nests, a behavior shared by many Myrmhopla species. Unlike ground-nesting ants, these are true tree-dwellers that rarely come down to the forest floor. They belong to the sexpinosa-group within Myrmhopla, characterized by their well-developed spines and arboreal lifestyle ^[3].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Endemic to northern Australia, specifically Cape York Peninsula (Lockerbie Scrub, Bamaga, Jardine River, Iron Range, Mt Tozer). They inhabit the lower arboreal zone in tropical rainforest areas, building nests between leaves approximately 2-3 meters above ground. Colonies have also been found inside bamboo internodes ^[2][1].
• Colony Type: Single-queen colonies (monogyne). Each colony maintains a single nest with no satellite nests, they do not build multiple nests per colony ^[3][4].
  • Colony: Monogyne
• Size & Growth:
  • Queen: 11.3-13.10mm ^[2][1]
  • Worker: 9.78-11.95mm ^[1][2]
  • Colony: Unknown for this specific species, related Polyrhachis species typically reach several hundred workers
  • Growth: Moderate, based on typical Polyrhachis development patterns
  • Development: Estimated 8-12 weeks based on genus-level data for Myrmhopla species (Development time is inferred from related arboreal Polyrhachis species, specific timing for this species has not been documented. Cocoons are present, which may extend development slightly compared to naked pupae.)
• Antkeeping:
  • Temperature: Keep around 24-28°C. Being from tropical northern Australia, they prefer warm conditions. A gentle gradient allowing them to move between warmer and cooler areas is ideal
  • Humidity: Moderate to high, arboreal ants prefer humid conditions but not saturated. Aim for 60-80% relative humidity with good ventilation to prevent mold
  • Diapause: Likely minimal or none, being a tropical Australian species from Cape York, they probably do not require a true hibernation. However, a slight cooling period during winter months may be beneficial
  • Nesting: Arboreal setup is essential. These ants naturally nest between leaves and in hollow stems. In captivity, they do well in vertical or tilted setups that mimic trees, Y-tong nests, bamboo sections, or naturalistic setups with plants they can use for silk binding work well. They need vertical space and materials they can manipulate with silk ^[3][4][2]
• Behavior: Generally calm and non-aggressive for a spiny ant. They are arboreal and spend most of their time in the upper portions of their enclosure. Workers are moderately active foragers that patrol plants and branches. They are not known for being particularly defensive but will use their spines if threatened. Escape risk is moderate, they are medium-sized ants but being arboreal, they will explore vertical surfaces and may climb out of unsecured setups. Their use of silk means they can seal small gaps with webbing, so escape prevention should be good quality.
• Common Issues: arboreal nature makes them prone to escaping if enclosure top is not secure, they will climb and explore, nesting in bamboo means they need appropriate diameter tubes or stems, too large and they may not feel secure, silk production can clog small gaps and airways in formicaria if not monitored, humidity that is too high without ventilation causes mold problems that can devastate colonies, being tropical, prolonged cool temperatures below 20°C can slow or stop brood development

Housing and Nest Setup

Polyrhachis glabrinota requires an arboreal-focused setup rather than a typical horizontal formicarium. In the wild, they nest between leaves and in bamboo stems 2-3 meters above ground, so your setup should mimic this vertical orientation. Y-tong (acrylic) nests work well, especially when tilted or mounted vertically. Bamboo sections of appropriate diameter (slightly larger than worker width) are ideal and closely mimic their natural nesting sites. You can also use naturalistic setups with live or artificial plants where they can build silk nests between leaves. The key is providing vertical space and materials they can manipulate. Because they produce silk to bind nest materials, include some flexible materials like cotton, moss, or leaf pieces they can work with. A water tube for humidity is important, but position it so it doesn't flood the nesting area ^[2][3].

Feeding and Diet

Polyrhachis ants are omnivorous with a preference for protein sources. In captivity, they readily accept typical ant foods including sugar water or honey as an energy source, and protein-rich foods like small insects (fruit flies, small crickets, mealworms), boiled egg, or cat food. Being arboreal, they may prefer to forage on elevated surfaces rather than the nest floor. Feed them a few times per week, offer protein 2-3 times weekly and keep a constant sugar water source available. Remove uneaten protein after 24-48 hours to prevent mold. Some keepers report that Polyrhachis species are less interested in seeds than some other genera. Observe your colony's preferences and adjust feeding accordingly.

Temperature and Heating

Being from tropical northern Australia, P. glabrinota prefers warm conditions. Aim for temperatures between 24-28°C during the active season. A slight temperature gradient (warmer on one side, cooler on the other) allows the colony to self-regulate. You can achieve this with a small heating cable or heat mat placed on one side of the enclosure, but always ensure there's an unheated area they can retreat to. Avoid temperatures below 20°C for extended periods, this species is not adapted to cold conditions. Room temperature in most homes (22-24°C) may be adequate, but you may need supplemental heating to reach optimal range. Monitor colony behavior, if workers are clustered near the heat source, they're telling you they want it warmer. ^[2]

Humidity and Water

These arboreal ants need moderate humidity around 60-80%. Unlike ground-nesting species that need damp substrate, P. glabrinota gets moisture primarily from food and a water source. Provide a water tube or small dish that they can access. Mist the enclosure occasionally, but avoid creating standing water or overly damp conditions that lead to mold. Good ventilation is important, stagnant, humid air causes fungal problems that can kill colonies. The arboreal lifestyle means they're adapted to drier conditions than ground-nesting ants, so when in doubt, lean slightly drier rather than wetter. ^[2]

Colony Structure and Growth

P. glabrinota forms single-queen colonies with no satellite nests, the entire colony lives in one location. This is important for keepers to understand because you won't see the kind of expansion behavior seen in species that branch out into multiple nests. Colonies likely grow to several hundred workers over time, though exact maximum size is undocumented for this species. The presence of cocoons (they wrap their pupae in silk) means development may take slightly longer than species with naked pupae, as the cocoon must be constructed before the adult emerges. Be patient with growth, Polyrhachis species are not fast growers compared to some genera, but they are long-lived and colonies can persist for many years ^[3][4].

Behavior and Handling

These ants are generally calm and not particularly aggressive. Their main defense is their spines, they may curl into a ball if handled roughly, using the spines as protection rather than actively stinging. Workers are moderately active and will explore their environment, particularly vertically. They are skilled climbers and will explore any branches, plants, or surfaces in their enclosure. Because they produce silk, you may notice them binding materials together or sealing small gaps. This is normal behavior and indicates a healthy, active colony. They are not known for major escape problems compared to tiny ants, but always use a secure lid, any gap is an opportunity.

Frequently Asked Questions

References