Rhopalomastix murphyi

Quick Summary

• Difficulty: Hard
• Origin & Habitat: Singapore (Indomalaya Region). The type series was collected in an abandoned plantation forest from the bark of a durian tree (Durio zibethinus) ^[1]. They nest in the soft inner bark, which is 2-5 mm thick, and are active foragers during daytime ^[2].
• Colony Type: Multiple queens per colony (polygynous). The type colony had numerous workers and multiple dealate queens, indicating stable polygyny ^[1][2].
• Size & Growth:
  • Queen: 1.94-2.46 mm total length ^[1]
  • Worker: 1.59-2.07 mm total length ^[1]
  • Colony: At least 138 workers in a small nest fragment, mature colonies likely reach several hundred workers ^[2]
  • Growth: Moderate (inferred from small tropical Myrmicinae)
  • Development: Estimated 5-8 weeks at tropical temperatures (25-28°C). Specific data unavailable, but development is relatively fast compared to larger ants (Development time is estimated based on genus‑level patterns for small tropical Myrmicinae.)
• Antkeeping:
  • Temperature: Keep at 24-28°C. As a tropical species from Singapore, they need warmth year‑round and can tolerate up to about 32°C. Avoid temperatures below 22°C, which will slow growth
  • Humidity: The natural nest substrate (inner bark) is soft and crumb‑like. Provide moderate to high humidity by keeping the nest area slightly moist but not wet. A humidity gradient is recommended: one drier side and one slightly moist side ^[2]
  • Diapause: No diapause required. They are active year‑round
  • Nesting: These ants prefer tight, narrow chambers that mimic bark crevices. Use Y‑tong (AAC), plaster, or 3D‑printed nests with thin chambers, or naturalistic setups with cork bark or wood slabs. Test tubes work for founding if kept dark and snug. Avoid tall chambers, they feel insecure in open spaces. ^[2][1]
• Behavior: Rhopalomastix murphyi is notably more aggressive than other Rhopalomastix species, workers have a functional sting and will use it if disturbed ^[2]. They are diurnal foragers and will explore outworlds actively. Despite their tiny size, they defend their territory fiercely. Escape prevention is critical: they can squeeze through cracks smaller than 1 mm. Use fine mesh or tight‑fitting lids.
• Common Issues: aggressive workers with a functional sting, handle with care, use gloves if needed, very small size makes them prone to escaping through tiny gaps, seal all junctions meticulously, tropical species needs constant warmth, cold spells can stall development or kill the colony, founding queens may be difficult to obtain, wild‑caught colonies often come with scale insects or other hitchhikers, natural bark‑nesting behavior makes it tricky to move them into artificial nests, they may refuse to settle in open chambers

Housing and Nest Setup

Rhopalomastix murphyi is a bark‑nesting ant that in the wild carves tunnels under the thin (2-5 mm) inner bark of trees ^[2]. To mimic this, use a nest with very narrow chambers, Y‑tong (AAC), plaster, or 3D‑printed nests work well, as do naturalistic setups with flat pieces of cork bark or rotting wood sandwiched between glass. Founding colonies can start in a test tube, but make sure the cotton plug is packed tightly and the tube is kept dark. As the colony grows, transfer them to a formicarium with chamber heights of 2-4 mm. Because the workers are only 1.6-2.1 mm long, they can squeeze through tiny gaps, use fine stainless steel mesh or fluon barriers, and always check seals. Avoid acrylic nests, as these ants prefer the porous texture of Y‑tong or wood. ^[2][1]

Feeding and Diet

In the wild, Rhopalomastix murphyi associates with armored scale insects (Andaspis numerata) and almost certainly feeds on honeydew ^[2]. In captivity, provide a constant source of sugar, honey water or sugar water (1:4 ratio) works well. For protein, offer small insects such as fruit flies, pinhead crickets, or freshly killed mealworm pieces. Protein should be given 2-3 times per week, and any leftovers removed after 24 hours to prevent mold. They will also accept commercial ant food or boiled egg yolk. Because they are tiny, avoid large prey that could rot and foul the nest. ^[2]

Temperature and Seasonal Care

As a tropical species from Singapore, Rhopalomastix murphyi needs warmth year‑round. Keep the nest area at 24-28°C for optimal brood development. They can tolerate short periods up to 32°C but should be protected from direct sun or heat sources that cause drying. If room temperature drops below 22°C, use a heating cable or mat placed under or beside the nest, never on top, as that can dry out the nest. No diapause or hibernation is needed, they will remain active and grow all year.

Behavior and Defense

Rhopalomastix murphyi is one of the few Myrmicinae to keep a functional sting, and it does not hesitate to use it ^[2]. Workers are diurnal and will leave the nest to forage on the outworld surface. When threatened, they raise their gaster and attempt to sting, the sting is not medically significant but can be surprising. They are also more aggressive than other Rhopalomastix species, researchers noted that they sting readily, unlike their more timid relatives ^[2]. A curious behavior observed in this species is head‑bobbing during silk application (though silk is unlikely to be used in artificial nests) ^[2]. Because of their aggression, use gloves or soft forceps when maintaining the outworld, and avoid blowing into the nest or jarring it. ^[2]

Colony Structure and Growth

This species is polygynous, the type series came from a large colony with multiple dealate queens ^[1][2]. Unlike monogyne species, multiple queens cooperate in the same nest, which speeds up colony growth and makes the colony more resilient to queen loss. One observed colony had 138 workers and 14 males occupying a wood fragment of only 18.5 cm² volume (14.8 cm³), indicating that they can pack tightly in small spaces ^[2]. Growth rate is moderate for a tropical myrmicine: from a founding queen, first workers appear in about 5-8 weeks at 25-28°C. Mature colonies likely number a few hundred workers. The ability to keep multiple queens means you can expect faster growth than single‑queen setups. ^[2][1]

Frequently Asked Questions

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References