Apterostigma carinatum

Apterostigma carinatum

Apterostigma carinatum is a small fungus-growing ant from the tribe Attini, ants that cultivate fungus gardens for food instead of hunting directly. They live in the tropical lowlands of Colombia, Ecuador, and Brazil ^[1][2][3]. You can recognize workers by their elongate petiole (the narrow waist segment) and the presence of a dorsal mesosomal carina, a raised ridge running along the back ^[1]. They inhabit primary and secondary rainforests from sea level up to 400 meters elevation, with records from both undisturbed forest and disturbed areas including logged forest, burnt forest, and pasture ^[1][2].

As non-leaf-cutting fungus growers, they cultivate symbiotic fungus on insect frass and plant debris rather than cutting leaves ^[1]. This makes them challenging to keep in captivity compared to generalist feeders. They are cryptic ants that prefer damp, shaded microhabitats in the leaf litter and soil of tropical forests ^[2].

Quick Summary

• Difficulty: Hard
• Origin & Habitat: Tropical lowland rainforests of Colombia, Ecuador, and Brazil (Pará), found in primary and secondary forest, logged areas, and pasture from 50-400m elevation ^[1][2][4].
• Colony Type: Likely single-queen (monogyne) based on typical Apterostigma patterns, but unconfirmed for this species.
• Size & Growth:
  • Queen: Unknown, likely 5-7mm based on typical Apterostigma morphology ^[3].
  • Worker: Unknown, likely 3-4mm based on genus patterns ^[3].
  • Colony: Unknown, Apterostigma colonies typically remain small, likely under 100 workers.
  • Growth: Slow
  • Development: Unknown, estimated 8-12 weeks based on related fungus-growing ants. (Fungus-growing ants typically develop slower than predatory species. First workers (nanitics) may emerge slightly faster but colonies grow slowly.)
• Antkeeping:
  • Temperature: 24-28°C estimated from tropical lowland distribution. Keep stable with minimal fluctuation ^[1][2].
  • Humidity: High humidity 70-80%. Maintain damp substrate similar to tropical forest floor conditions.
  • Diapause: No, tropical species that remains active year-round ^[3].
  • Nesting: Naturalistic setup with soil or rotting wood. They nest in soil and leaf litter in nature ^[2].
• Behavior: Cryptic and slow-moving with deliberate foraging behavior. Non-aggressive. Small size means escape prevention must be excellent, use fine mesh barriers and Fluon-coated surfaces.
• Common Issues: fungus garden contamination or failure is the primary cause of colony death in captive fungus-growing ants., difficulty obtaining founding queens, they are rarely collected and founding behavior is unconfirmed., sensitivity to desiccation, colonies die quickly if humidity drops below tropical forest levels., slow growth rate requires patience, colonies may take years to reach 50 workers.

Natural History and Distribution

Apterostigma carinatum inhabits the tropical lowlands of northwestern South America. In Colombia, they are found in the departments of Valle del Cauca, Nariño, Chocó, and Vaupés ^[1][4][5]. The species also occurs in Ecuador and has been recorded in Pará, Brazil ^[1][2].

Collection records show they live at elevations from 50 meters (Barbacoa, Nariño) up to 400 meters (Rio Tatabro, Valle del Cauca) ^[1][6]. They show flexibility in habitat use, found in undisturbed primary forest but also in logged forest, burnt forest, secondary growth, and even pasture ^[2]. This suggests they can tolerate some habitat disturbance, though they remain dependent on forest floor conditions with suitable nest sites and fungus-growing substrates.

Nest Preferences and Setup

In nature, these ants nest in soil and leaf litter on the forest floor ^[2]. They require humid, stable microhabitats that support their fungus gardens.

For captive care, use a naturalistic setup with a soil-based nest or plaster nest that can hold moisture. Include a foraging area with leaf litter and small pieces of rotting wood to mimic their natural environment. The nest must maintain high humidity, the substrate should feel damp to the touch but not waterlogged. Provide a temperature gradient by placing a heating cable on one side of the nest, keeping the warm side around 26-28°C and allowing a slight drop to 24°C on the cool side.

Fungus Cultivation and Feeding

As members of the Attini tribe (fungus-growing ants), Apterostigma carinatum cultivate symbiotic fungus on organic substrates ^[1]. Unlike leaf-cutter ants, they do not cut leaves but instead collect insect frass (insect droppings), dead plant material, and other debris to feed their fungus gardens.

In captivity, provide small amounts of dried leaves, flower petals, or insect frass. They also need protein sources, offer tiny pieces of insects, fish flakes, or boiled egg which the workers will process to feed the fungus. Never allow the fungus garden to dry out or become contaminated with mold. If the fungus turns gray, white, or develops black spots, the garden is failing and the colony is in danger.

Temperature and Environmental Care

Being from tropical lowland forests, they require warm stable temperatures. Aim for 24-28°C with minimal fluctuation ^[1][2]. Sudden temperature drops below 20°C can stress the fungus garden and kill the colony.

High humidity is critical, maintain 70-80% relative humidity. This requires damp nest material and limited ventilation. However, avoid stagnant air which promotes mold. Use small ventilation holes with fine mesh to balance humidity and air exchange. Check the fungus garden daily, it should look healthy and slightly moist, never dry or moldy.

Behavior and Temperament

These ants are cryptic and slow-moving, spending much of their time tending the fungus garden rather than foraging aggressively. They are not known to sting and show little defensive behavior.

Because of their small size (likely 3-4mm), escape prevention must be excellent. Use Fluon (a slippery barrier) on the upper walls of the foraging area and fine mesh (less than 1mm) on any ventilation. Even tiny gaps in lids or tubing will allow workers to escape. ^[3]

Frequently Asked Questions

References