Polyrhachis inermis

Polyrhachis inermis

Polyrhachis inermis is a small, black ant species belonging to the subgenus Myrma, part of the inermis-group. Workers measure approximately 4.5-5mm and are entirely black in color, distinguishing them from similar species like P. orsylla which has reddish-brown tibiae. This species is found throughout the Indomalaya region including Borneo, Sulawesi, the Philippines, Malaysia, Singapore, and Thailand ^[1][2]. As canopy-dwelling ants, they are typically found in tropical rainforests where they inhabit the forest layer rather than the ground ^[3].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Tropical Southeast Asia, found in Borneo, Sulawesi, Philippines, Malaysia, Singapore, and Thailand. They inhabit tropical rainforests, particularly the canopy layer, and have been collected in alluvial forest environments ^[4][3].
• Colony Type: Likely monogyne (single queen) based on typical Polyrhachis patterns, though colony structure has not been directly documented for this specific species.
  • Founding: Claustral
• Size & Growth:
  • Queen: Undocumented, estimated 7-9mm based on related Polyrhachis species
  • Worker: 4.5-5mm (approximately 2¼ lines) ^[1]
  • Colony: Unknown, related Polyrhachis species typically reach several hundred workers
  • Growth: Moderate, typical for tropical ants
  • Development: Estimated 6-8 weeks at optimal tropical temperatures based on genus patterns (Development time inferred from related tropical Polyrhachis species, direct measurements unavailable for this species)
• Antkeeping:
  • Temperature: Keep at 24-28°C, they are tropical ants requiring warm, stable conditions ^[4]
  • Humidity: High humidity (70-85%), rainforest species that naturally inhabits damp canopy environments. Keep nest substrate consistently moist but not waterlogged.
  • Diapause: No, as a tropical species, they do not require hibernation. Maintain warm temperatures year-round.
  • Nesting: Canopy-dwelling species. In captivity, they do well in naturalistic setups with vertical spaces or Y-tong nests with moisture. They prefer humid conditions with some vertical climbing space.
• Behavior: Generally peaceful and non-aggressive compared to some other Polyrhachis species. They are arboreal (tree-dwelling) ants that prefer to stay in elevated spaces. Workers are active foragers in the canopy layer. Escape prevention is important as they are small and agile, use fine mesh barriers. They likely accept sugar sources and small prey, though specific feeding preferences are unconfirmed.
• Common Issues: tropical species requires consistent warmth, cold temperatures can slow or stop brood development, high humidity needs mean mold can be an issue if ventilation is poor, small size makes escape prevention critical, use fine mesh and tight-fitting lids, canopy-dwelling nature means they need vertical space in their enclosure, slow founding means colonies take time to establish, patience is required

Housing and Nest Setup

Polyrhachis inermis is a canopy-dwelling species, so they do best in setups that provide vertical space for climbing. A Y-tong (acrylic) nest works well, or you can use a naturalistic setup with plants and branches. Because they come from humid tropical rainforests, keep the nest substrate consistently moist but not flooded. A small water reservoir connected to the nest helps maintain humidity. Provide a foraging area with some height so workers can explore. Escape prevention is critical, these small ants can squeeze through surprisingly small gaps, so use fine mesh on all openings. ^[3][4]

Feeding and Diet

Like most Polyrhachis species, P. inermis is likely omnivorous. Offer sugar water or honey as a constant energy source. For protein, provide small insects like fruit flies, pinhead crickets, or mealworms. In the wild, they forage in the canopy and may tend honeydew-producing insects. Feed them small prey items 2-3 times per week, and keep a sugar source available at all times. Remove uneaten prey after 24 hours to prevent mold.

Temperature and Humidity

These are tropical ants that need warm, humid conditions. Keep temperatures between 24-28°C year-round, they do not tolerate cool conditions well. A small heating cable on one side of the nest can help maintain warmth if your room temperature is below 24°C. Humidity should stay around 70-85%. Mist the nest area regularly and keep the water reservoir filled. Avoid placing the nest near air conditioning or drafty windows. Unlike temperate species, they do not need any cooling period or hibernation. ^[4]

Colony Development

A newly mated queen will seal herself in a chamber and lay eggs after a few weeks. She feeds the first brood using her stored fat reserves, this is called claustral founding. The first workers (nanitics) will be smaller than mature workers and appear after 6-8 weeks at optimal temperatures. After the nanitics emerge, the colony grows gradually. Expect the first major workers (larger, fully developed workers) to appear a few months later. Colonies develop moderately fast once established, but the founding phase requires patience.

Behavior and Temperament

Polyrhachis inermis is generally peaceful and less aggressive than some other Polyrhachis species. Workers are active foragers that explore their territory methodically. As arboreal ants, they prefer to stay elevated and will often travel along branches or plants in their enclosure. They are not known for stinging and pose no danger to keepers. Their small size and agile movement make them interesting to watch. They are not escape artists in the sense of being particularly strong, but their tiny size means they can slip through small gaps, excellent escape prevention is still essential. ^[3]

Frequently Asked Questions

References