Rhopalomastix murphyi

Rhopalomastix murphyi

Rhopalomastix murphyi is a tiny bark-nesting ant species native to Singapore, first described in 2018. Workers are remarkably small at just 1.6-2mm in total length, with a uniform yellowish-brown coloration and slightly darker head and mesosoma . These ants are monomorphic, all workers look essentially the same size with little variation. They nest under the bark of trees, particularly durian trees, where they create tunnels in the soft inner bark layer ^[1]. The colony type was collected from an extensive area of bark on a durian tree in an abandoned plantation forest, indicating they can form relatively large colonies .

What makes Rhopalomastix murphyi particularly interesting is their mutualistic relationship with armored scale insects (Andaspis numerata). The ants live alongside these scale insects and likely tend them for honeydew, similar to how other ants tend aphids ^[1]. This species is also notably more aggressive than other Rhopalomastix species, they have retained a functional sting and will readily use it when threatened ^[1]. This is unusual because many Myrmicinae ants have lost their sting, making these ants more capable of defending themselves than many related species.

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Singapore (Indomalaya Region). Found in abandoned plantation forests, nesting under tree bark, particularly on durian trees (Durio zibethinus) ^[1].
• Colony Type: Multi-queen colonies. The type series came from a large colony with numerous workers and multiple dealate queens . This suggests they are polygynous (multiple queens per colony).
  • Colony: Polygyne
  • Founding: Claustral
• Size & Growth:
  • Queen: 1.94-2.46mm total length (HL 0.42-0.45mm, HW 0.38-0.42mm)
  • Worker: 1.59-2.07mm total length (HL 0.40-0.44mm, HW 0.36-0.41mm)
  • Colony: At least 138 workers observed in a small nest fragment, colonies can likely reach several hundred workers ^[1]
  • Growth: Moderate, based on typical Myrmicinae development
  • Development: Estimated 5-8 weeks at tropical temperatures (25-28°C). This is a small Myrmicinae species, so development is relatively fast compared to larger ants (Development time is estimated based on genus-level patterns for small tropical Myrmicinae. Specific development data for this species is not available.)
• Antkeeping:
  • Temperature: Keep at 24-28°C (tropical species from Singapore). They can tolerate slightly warmer conditions but avoid temperatures above 32°C. Room temperature in most homes (22-26°C) should work well
  • Humidity: Bark-dwelling ants prefer moderate to high humidity (60-80%). Keep the nest substrate slightly moist but not waterlogged. The inner bark they naturally nest in is 2-5mm thick and relatively soft ^[1]
  • Diapause: No diapause required. As a tropical species from Singapore, they do not need a hibernation period. They remain active year-round
  • Nesting: These are bark-nesting ants. In captivity, they do well in small acrylic nests, Y-tong (AAC) setups, or naturalistic setups with bark pieces. They prefer tight, narrow chambers that mimic the tight spaces under tree bark. Test tubes can work for founding colonies but may need to be modified to provide the tight spaces they prefer ^[1]
• Behavior: Rhopalomastix murphyi is notably aggressive compared to other Rhopalomastix species. Workers have retained a functional sting and will sting if threatened ^[1]. They are active foragers, with many workers venturing outside the nest during daytime to tend scale insects and forage ^[1]. They are small ants but determined defenders of their territory. Escape prevention is important, their small size means they can squeeze through small gaps, though they are not as prone to escaping as some truly tiny species. They are best housed in secure enclosures with tight-fitting lids.
• Common Issues: aggressive behavior and functional sting means they can deliver painful stings, handle with care and use gloves when necessary, small colony size at founding means growth can be slow and beginners may lose patience, tropical species requires consistent warmth, cold temperatures will slow or stop development, escape risk due to small size, use fine mesh barriers and check lid seals regularly, wild-caught colonies may arrive with scale insects or other commensals that could affect colony health

Housing and Nest Setup

Rhopalomastix murphyi is a bark-nesting ant, so your setup should mimic their natural environment under tree bark. For founding colonies, a small test tube setup works well, make sure the water reservoir is appropriately sized and the cotton is packed tight to prevent flooding. As the colony grows, consider moving them to a small acrylic formicarium or Y-tong (AAC) nest with narrow chambers and passages. These ants prefer tight spaces, the natural tunnels they create in bark are just a few millimeters thick ^[1]. A naturalistic setup with pieces of cork bark or wood can also work well, giving them the bark crevices they naturally prefer. Whatever nest type you choose, ensure it has good escape prevention, these tiny ants can squeeze through surprisingly small gaps.

Feeding and Diet

In the wild, Rhopalomastix murphyi associates with armored scale insects (Andaspis numerata) and likely feeds on the honeydew these insects produce ^[1]. In captivity, you should offer a varied diet including sugar sources (sugar water, honey, or diluted honey water) and protein sources. They will likely accept small insects like fruit flies, small crickets, and mealworms. Given their small size, prey items should be appropriately sized, tiny insects and arthropods are most appropriate. Feed protein 2-3 times per week and keep a sugar source available at all times. Remove uneaten prey after 24-48 hours to prevent mold issues.

Temperature and Seasonal Care

As a tropical species from Singapore, Rhopalomastix murphyi requires warm conditions year-round. Keep the nest area at 24-28°C for optimal brood development. They can tolerate temperatures up to around 32°C but should be kept away from direct heat sources that could cause drying. Unlike temperate species, they do not require a diapause or hibernation period, they remain active throughout the year. If your room temperature drops below 22°C, consider using a heating cable or heating mat on one side of the nest to maintain warmth. Place heating under or to the side of the nest, never directly on top where it can cause excessive drying.

Behavior and Defense

Rhopalomastix murphyi is notably more aggressive than other Rhopalomastix species, they have retained a functional sting and are not afraid to use it ^[1]. Workers will actively defend the nest and can deliver a noticeable sting if provoked. When handling these ants or working with their colony, use caution and consider wearing gloves. They are active foragers, with many workers visible outside the nest during daytime ^[1]. This means they are not shy about exploring their outworld. They are not overly skittish but will readily escalate to stinging if they feel threatened. This aggression also means they may dominate food sources and defend territory aggressively against other ants.

Colony Structure and Growth

This species is polygynous, meaning colonies naturally have multiple queens . The type series came from a colony with numerous workers and multiple dealate queens, indicating they live in multi-queen societies . This can be an advantage for keepers, having multiple queens means the colony can grow faster and is more resilient to queen loss. However, it also means you should not expect queens to fight as they might in monogyne species. Colony growth is moderate, starting from a single queen, you can expect first workers (nanitics) in 5-8 weeks under optimal conditions. Mature colonies can reach several hundred workers. The observed colony had 138 workers in just 18.5cm² of nesting space, suggesting they can maintain dense populations in relatively small areas ^[1].

Frequently Asked Questions

References