Cyphomyrmex rimosus

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to Central and South America (Argentina to southern Mexico), introduced to the southeastern US (Florida, Georgia, Alabama, Mississippi, Texas), and the Galápagos Islands. Found in diverse habitats from dry open areas to lowland rainforests, typically in damp soil microhabitats under stones, logs, or in rotting wood ^[1][2].
• Colony Type: Facultatively polygynous, typically single queen but colonies may have 2-4 queens. Queens are monandrous (mate only once) ^[2][3].
• Size & Growth:
  • Queen: size data unavailable
  • Worker: 3.3-3.5mm total length ^[2]
  • Colony: Typically under 100 workers, up to 300+ in mature colonies ^[2]
  • Growth: Moderate
  • Development: 6-10 weeks (estimated based on related attine species) (Development time is not directly studied for this species. Semi-claustral founding means queens must forage during colony establishment, which extends the development timeline compared to claustral species.)
• Antkeeping:
  • Temperature: Keep at 24-28°C. This is a tropical species that thrives in warm, humid conditions. Room temperature in most homes is often suitable, but a heating cable on one side of the nest can help maintain optimal warmth ^[2].
  • Humidity: High humidity required, they prefer damp soil and nest in moist microhabitats. Keep the nest substrate consistently moist but not waterlogged. These ants are found in areas with appropriate moisture, temperature, and organic matter conditions ^[4].
  • Diapause: No, being tropical, they do not require hibernation. However, activity may slow slightly during cooler winter months in temperate regions.
  • Nesting: Use a naturalistic setup with moist substrate (soil or sand mix) or a Y-tong/plaster nest. They nest in soil, under stones, or in rotting wood in the wild. Provide damp substrate and avoid drying out. Test tubes can work but may need modification to maintain humidity ^[5].
• Behavior: These ants are not aggressive and rely on cryptic defense, when disturbed, workers often play dead (thanatosis). They are highly mobile and will rapidly evacuate the nest if threatened, carrying their brood and fungal garden. Workers forage individually on the surface, collecting small insect parts, caterpillar droppings, and other organic matter. They practice age polyethism: young workers stay in the nest tending the fungus and brood, while older workers forage and defend. Escape risk is moderate, their small size means they can slip through small gaps, so ensure barrier precautions are adequate.
• Common Issues: fungus garden failure, the symbiotic fungus is essential, without it, the colony will die. Never disturb or discard the fungal garden., drying out, these ants need constant moisture. Dry conditions will kill the fungus and the colony., colony stress from disturbance, they are sensitive to nest disruption and may abandon the nest if stressed., small colony size, colonies grow slowly and remain small compared to many common ant species, which can frustrate beginners.

The Fungus Garden - The Heart of the Colony

Cyphomyrmex rimosus is a yeast-farming attine ant. Unlike leaf-cutter ants that grow fungi on leaf pieces, this species cultivates its fungal partner on a substrate of insect feces (especially millipede frass), dead insects, and other organic debris. The fungus grows as small yeast-like nodules (0.25-0.50mm diameter) rather than mycelium. This is critical for keepers: the fungus is the colony's sole food source. Larvae eat exclusively fungus, while adult workers also consume plant sap and nectar. Never remove or discard the fungal garden, it is essential for colony survival. If the fungus dies, the colony will not survive. The fungal cultivar can sometimes be shared with other Cyphomyrmex species if colonies are kept in proximity ^[7][8][9].

Feeding and Diet

In captivity, you must provide the substrate materials for fungus cultivation. Offer small pieces of dead insects (flightless fruit flies, small crickets, mealworm pieces), insect feces (caterpillar droppings are ideal), or other organic matter. You can also offer a small amount of honey or sugar water as a supplemental energy source for workers, but the primary food must be the organic substrate for the fungus. Some keepers report success with specially prepared substrates like oat flour mixed with water, but the most reliable approach is providing natural insect-derived materials. Remove uneaten organic matter after a few days to prevent mold. Workers will actively forage on plant sap and nectar if available ^[7][10].

Semi-Claustral Founding

Unlike many ants where queens seal themselves in and survive on stored fat, C. rimosus queens are semi-claustral, they must leave the nest to forage for food during the founding phase. Newly-mated queens contain about 11% fat by dry weight, which is not enough to survive until workers emerge without foraging. This makes colony founding more challenging in captivity. Queens search for suitable nesting sites in soil or under objects, then begin cultivating fungus on collected substrate. Most founding attempts fail because the queen cannot find adequate substrate. If you're starting from a dealate queen, provide small pieces of insect material immediately ^[6][7].

Temperature and Humidity

As a tropical species, C. rimosus requires warm and humid conditions. Keep the nest at 24-28°C with high humidity. The substrate should remain consistently moist, these ants are found in damp microhabitats in the wild. A hydration system (like a water reservoir connected to the nest) works well to maintain humidity. Avoid both drying out and waterlogging. Room temperature in heated homes (around 22-24°C) is often suitable, but you may need a small heating cable on part of the nest to reach optimal temperatures. Monitor colony activity, if workers cluster together excessively, they may be too cold, if they abandon the fungus garden, it may be too dry or hot ^[2][4].

Behavior and Defense

These are docile, non-aggressive ants. Their primary defense is crypsis, when disturbed, workers play dead (thanatosis), curling up and remaining motionless. They may also posture defensively by raising their forelegs and opening their mandibles. More significantly, they are highly mobile: when threatened, workers rapidly evacuate the nest, carrying the brood and fungal nodules. This makes them excellent escape artists in captivity, always use excellent barrier precautions. They also practice age polyethism: young workers remain in the nest for 3-4 weeks tending the fungus and brood, while older workers forage outside and defend the colony ^[7][11].

Colony Structure and Queens

C. rimosus colonies are typically small with usually fewer than 100 workers, though colonies can grow to 300+ individuals. Colonies are usually monogynous (single queen) but can be polygynous with 2-4 queens. Queens are monandrous, meaning they mate only once and store the sperm for life. This affects colony dynamics, there is only one patriline in the colony. Colony foundation is haplometrotic (single queen founding), though multiple dealate females may sometimes associate temporarily. The species shows high colony mobility and will readily relocate if conditions deteriorate ^[2][3][12].

Frequently Asked Questions

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References