Polyrhachis foreli

Polyrhachis foreli

Polyrhachis foreli is a medium-sized rainforest ant native to northern Queensland, Australia and New Guinea. Workers measure 7-10mm and queens reach 10-11mm, making them one of the larger Polyrhachis species. They are striking ants with a black body and distinctive spines protruding from the pronotum, mesonotum, propodeum, and petiole. Their legs and antennae may show reddish-brown coloration. This species belongs to the subgenus Myrma and is part of the relucens species-group. In the wild, they nest in rotting logs, tree stumps, epiphytes, or directly in the ground in rainforest habitats ^[1]. A notable trait is their Blochmannia bacterial symbiont, which they acquire by tending sap-feeding insects, this relationship helps them process nitrogen from their honeydew diet ^[2][3].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Rainforest of northern Queensland, Australia and New Guinea. They inhabit the wet tropics from Iron Range on Cape York Peninsula south to Mission Beach and Hinchinbrook Island, as well as disjunct Papuan populations on islands like Goodenough and Normanby ^[1].
• Colony Type: Single-queen colonies (monogyne). Queens have been collected from Saibai Island in Torres Strait, indicating established colonies in these areas ^[1].
  • Colony: Monogyne
  • Founding: Claustral
• Size & Growth:
  • Queen: 10.23-11.44mm ^[4]
  • Worker: 7.36-10.33mm ^[4]
  • Colony: Unknown, likely moderate-sized colonies typical for rainforest Polyrhachis
  • Growth: Moderate, estimated 6-10 weeks from egg to first worker based on genus patterns
  • Development: 6-10 weeks (estimated based on related Polyrhachis species) (Pupal cocoons are present, which is typical for the genus. Development time is inferred from related species in the subgenus Myrma.)
• Antkeeping:
  • Temperature: Keep around 24-28°C. As a rainforest species from tropical Queensland, they prefer warm, stable conditions. A gentle gradient allowing them to move between warmer and cooler areas is ideal.
  • Humidity: High humidity required, rainforest species. Keep nest substrate consistently moist but not waterlogged. Provide a humid outworld area as well.
  • Diapause: No, being a tropical rainforest species, they do not require hibernation. Keep temperatures stable year-round.
  • Nesting: They naturally nest in rotting wood, tree stumps, and epiphytes, but also in the ground. In captivity, a naturalistic setup with rotting wood pieces or a Y-tong/plaster nest works well. They are arboreal-nesting capable and may use silk to bind nest materials together ^[5].
• Behavior: Generally calm and non-aggressive for a large ant species. They are active foragers but not particularly defensive. Workers are medium-sized and can escape through small gaps, use standard escape prevention. They tend sap-feeding insects for honeydew and may harvest food bodies from plants. Their Blochmannia symbiont helps them process nitrogen from this diet. They spin cocoons for their pupae.
• Common Issues: high humidity is critical, drying out can kill colonies quickly, escape prevention needed, workers can fit through standard barrier gaps but monitor, tropical species cannot tolerate cool temperatures, keep above 24°C, slow colony growth compared to faster-developing species may frustrate beginners, wild-caught colonies may have parasites that affect survival in captivity

Housing and Nest Setup

Polyrhachis foreli is a versatile nester that in the wild uses rotting logs, tree stumps, epiphytes, and ground cavities. For captivity, a naturalistic setup with pieces of rotting wood works well, you can collect decayed wood from rainforest areas or purchase pre-treated nesting material. Alternatively, a Y-tong (acrylic) or plaster nest provides good humidity control. Because they come from humid rainforest environments, the nest must maintain high humidity while still having some ventilation to prevent mold. Place a water reservoir or moisture chamber connected to the nest area to maintain consistent dampness. The outworld should also have some humidity, and you can add live plants or moss to help maintain conditions. These ants can climb smooth surfaces well, so apply fluon or barrier gel to the rim of the formicarium. ^[1][5][7]

Feeding and Diet

Like other Polyrhachis in the subgenus Myrma, P. foreli has a mutualistic relationship with Blochmannia bacteria that helps them process nutrients from honeydew ^[2][3]. In captivity, offer sugar water or honey as a constant energy source. They also need protein, small insects like fruit flies, small crickets, or mealworms work well. In the wild, they have been observed harvesting food bodies from Ryparosa kurrangii seedlings during the day ^[6], so they may accept plant-based foods too. Feed protein 2-3 times per week and keep sugar water available at all times. Remove uneaten prey after 24 hours to prevent mold.

Temperature and Humidity

Being a tropical rainforest species from Queensland's wet tropics, P. foreli requires warm and humid conditions. Maintain temperatures between 24-28°C with minimal fluctuation. A heating cable on one side of the nest creates a gradient allowing workers to self-regulate their temperature preference. Humidity should be high, aim for 70-85% relative humidity in the nest area. The substrate or nest material should feel consistently moist but never waterlogged. Mist the outworld occasionally and monitor for condensation. If the nest dries out, workers may become sluggish and brood development will slow or stop. Conversely, excessive moisture without ventilation leads to mold problems. ^[1]

Colony Development

Queens are 10-11mm and claustral, they seal themselves in a chamber and raise the first workers alone using stored fat reserves. Pupal cocoons are present, which is typical for the genus ^[7]. First workers (nanitics) will be smaller than mature workers but should appear within 6-10 weeks under optimal conditions. Colony growth is moderate, expect several months before you have more than a dozen workers. As the colony grows, they may need more space and you can consider moving them to a larger formicarium. Unlike some Polyrhachis that form supercolonies, this species appears to maintain single-queen colonies.

Behavior and Temperament

Polyrhachis foreli is a relatively calm species compared to some other large ants. Workers are active foragers but not particularly aggressive or prone to stinging. They are primarily arboreal and have been observed foraging in the rainforest understory. Their spined morphology serves as a defensive adaptation, the multiple spines make them harder for predators to handle. Workers can live for several years, and queens can live for over a decade with proper care. They are not escape artists in the traditional sense but can fit through small gaps due to their size, standard barrier methods are usually sufficient. ^[1]

Frequently Asked Questions

References