Crematogaster cylindriceps

Quick Summary

• Difficulty: Expert
• Origin & Habitat: Southeast Asia, Philippines and Borneo (Kalimantan). Nests exclusively in living stems of climber plants (vines) such as Spatholobus and Uncaria species, typically found in both primary and secondary forests at heights ranging from 0.5m to 24m above ground ^[1].
• Colony Type: Polygynous, multiple queens live together in the same plant stem. Several dealated (wingless) queens have been found in adjacent internodes, and at least three queens occupy a single stem segment ^[1].
• Size & Growth:
  • Queen: 4.5-5.5 mm ^[1]
  • Worker: 1.75-2.00 mm ^[1]
  • Colony: Unknown
  • Growth: Unknown
  • Development: Unknown (No specific development data exists for this species.)
• Antkeeping:
  • Temperature: Keep at 24-28°C, aim for warm, stable conditions typical of tropical forest interiors. A gentle heat gradient allows workers to regulate their temperature.
  • Humidity: High humidity (70-80%), these ants live inside living plant stems in humid forest environments. The nest material should remain consistently moist but not waterlogged.
  • Diapause: Unknown, as a tropical species from Southeast Asia, they likely do not require hibernation. Maintain warm temperatures year-round.
  • Nesting: This species requires a naturalistic setup that mimics their natural stem-nesting habitat. Living plant stems or artificial stem-like structures (narrow glass or acrylic tubes) work best. The queen uses her phragmotic head to seal the nest, so provide appropriately sized chambers. Do not use large, open formicarium spaces, they need tight, enclosed spaces scaled to their tiny size.
• Behavior: Queens exhibit phragmotic behavior, their uniquely truncated head functions as a living door to seal the nest entrance, protecting the colony from invading ants, predators, and rival colonies ^[2]. This is a passive defense mechanism rather than active aggression. Workers are small and typically non-aggressive. They likely forage along plant stems and leaves, similar to other Crematogaster species. Escape prevention is critical due to their tiny 1.75-2mm worker size, use fine mesh barriers and tight-fitting lids. Colonies are polygynous with multiple reproductive queens coexisting.
• Common Issues: extreme rarity makes colonies nearly impossible to acquire, this species has never been collected in significant numbers since its original description, specialized stem-nesting requirement is difficult to replicate in captivity, they reject conventional nest types, tiny worker size means excellent escape prevention is essential, they can squeeze through standard barriers, polygynous structure may complicate colony establishment if queens are incompatible, no captive breeding data exists, wild-caught colonies may struggle in artificial conditions

The Phragmotic Queen

The most remarkable feature of Crematogaster cylindriceps is the queen's phragmotic head structure. Unlike typical ants, the queen's head is strongly truncated (flattened) at the front, creating a plug-like shape that can seal the nest entrance. This adaptation evolved under intense competition for nesting sites in plant stems, by sealing herself inside, the queen protects the colony from invading ants, predators, and rival colonies. This same phenomenon is seen in the related genus Colobopsis, where soldier castes have similarly modified heads. The queen's head in C. cylindriceps is so specialized that it represents a distinct evolutionary specialization rare among ants. In captivity, this means you should provide nest chambers with entrance holes that the queen can effectively seal with her head, slightly larger than her head width but not so large she cannot block it. ^[2][1]

Stem-Nesting Ecology

This is the only known Crematogaster species that nests exclusively inside living plant stems (vines and climbers). In the wild, colonies have been found in stems of Spatholobus (legume family) at 0.5-1m height in secondary forest, and in Uncaria (rubiaceae family) at around 24m height in primary forest. The internode diameters were 3-8mm inner diameter, tiny spaces. This species competes directly with other ant species (Cladomyrma hobbyi, Tetraponera species) for these limited nesting sites. In captivity, you cannot use standard soil nests or large acrylic formicaria. Instead, provide narrow glass or acrylic tubes (3-8mm diameter) or, ideally, maintain them in a naturalistic setup with actual vine material. The ants will need to move between stem sections and access the outworld through small openings. ^[1]

Polygynous Colony Structure

Crematogaster cylindriceps is polygynous, colonies contain multiple queens living together. Research found several dealated (wingless) queens in adjacent stem internodes, and at least three queens in a single internode. This is unusual because most Crematogaster species are monogyne (single queen). The polygynous structure likely evolved because the limited space inside plant stems cannot support a single large colony, multiple queens can spread across more internodes. In captivity, you may keep multiple queens together without the aggression seen in some species. However, this also means colonies may be harder to establish from scratch since multiple queens must be introduced to appropriate nesting space simultaneously. ^[1]

Housing and Nest Setup

Housing C. cylindriceps requires thinking differently than most ant species. Standard test tubes, Y-tong nests, and plaster formicaria are likely unsuitable. Instead, create a naturalistic setup with narrow channels that mimic plant stem internodes. Glass tubing with 3-8mm inner diameter works well, cut sections and connect them to create a branching network. Alternatively, you could maintain a living climber plant in a terrarium and allow the colony to nest naturally within the stems. The outworld should be small and connected via narrow tubing (3-4mm diameter) to prevent escapes. Use cotton or fine mesh at all connections. The queen needs a chamber where she can position herself to seal the entrance with her phragmotic head, this is behavioral enrichment she would have in the wild. ^[1]

Feeding and Diet

Like other Crematogaster species, C. cylindriceps likely has an omnivorous diet. They probably tend scale insects inside their stem nests (scale insects were not observed in studied colonies but this may be due to incomplete sampling). In captivity, offer sugar water or honey as a constant energy source. For protein, provide small live prey appropriate to their tiny worker size, fruit flies, pinhead crickets, or small mealworms. Since they nest in plant stems, they may also have access to nectar from the host plant, consider providing a small sugar source. Feed protein 2-3 times per week and ensure sugar water is always available. Remove uneaten prey within 24 hours to prevent mold in the humid setup. ^[1]

Temperature and Humidity

As a tropical species from Southeast Asia, C. cylindriceps requires warm, humid conditions. Keep temperatures in the range of 24-28°C. A slight temperature gradient (warm end around 28°C, cooler around 24°C) allows workers to regulate by moving between areas. Use a heating cable or mat on one side of the setup, placed on top of the nest material to avoid drying it out. Humidity should remain high at 70-80%, these ants live inside living plant stems in forest environments where humidity is constantly elevated. Mist the setup regularly and ensure the nest material stays moist but never waterlogged. Poor humidity will quickly stress these delicate ants. ^[1]

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