Acromyrmex subterraneus

Quick Summary

• Difficulty: Expert
• Origin & Habitat: Native to the Neotropical region: Argentina, Bolivia, Brazil, Paraguay, and Peru. Found in Atlantic Forest, Cerrado savanna, and eucalyptus plantations ^[1][2].
• Colony Type: Facultatively polygynous, colonies may have one queen or multiple queens (up to 14 observed). Workers accept additional queens through transport into the nest ^[9][10][13].
• Size & Growth:
  • Queen: ~10 mm body length ^[4]
  • Worker: Major workers up to 10 mm, head capsule widths range 0.98-2.47 mm ^[4][6]
  • Colony: Up to 6,782 workers documented ^[14]
  • Growth: Moderate
  • Development: Approximately 9 weeks (63 days) for first workers to emerge ^[15] (Eggs appear in week 1,larvae in week 3,pupae in weeks 6-7. First generation averages 2 workers, colonies reach 24 workers by week 13 ^[15].)
• Antkeeping:
  • Temperature: Maintain 25±2°C. Activity ceases below 10°C ^[9][8].
  • Humidity: Maintain 70-80% relative humidity. The fungus garden requires consistent moisture, provide water via test tube and ensure substrate remains damp but not waterlogged ^[9].
  • Diapause: No diapause required, being a tropical species, they remain active year-round if kept warm.
  • Nesting: Use a formicarium with a dedicated fungus chamber. Young colonies nest superficially (11-20 cm deep) with single fungus chambers of 0.5-1.5 liters ^[16]. Y-tong or plaster nests work well. Provide a foraging area for daily plant material.
• Behavior: Primarily nocturnal with foraging peaks between 8pm and 2am ^[6]. Workers show clear division of labor: minor workers (0.7-0.8 mm head capsule) tend fungus and brood, while larger workers handle foraging and cutting ^[17]. They use trail pheromones (methyl 4-methylpyrrole-2-carboxylate) and rely on individual memory over social cues when information conflicts ^[18][19]. They possess a functional sting but primarily defend via biting and chemical secretions including myrmicacin from the metapleural gland ^[20].
• Common Issues: Fungus garden collapse from improper humidity or contaminated plant material, ensure pesticide-free leaves and consistent moisture., High queen mortality during founding, approximately 45% die in the first 2 weeks, and only ~30% survive to produce first workers ^[15]., Parasitoid wasp Szelenyiopria talitae can parasitize larvae, look for dark coloration through the cuticle. Infected colonies typically collapse within 2-3 months ^[26]., Pathogenic fungus Escovopsis can infect gardens, maintain hygiene and remove waste promptly ^[23]., Temperatures below 10°C stop all foraging and can stress the colony ^[8]., Imidacloprid and other neonicotinoids inhibit grooming defenses and should never be used near colonies ^[27].

Housing and Setup

Acromyrmex subterraneus requires a setup that accommodates their fungus-farming lifestyle. The nest needs a dedicated fungus chamber that stays consistently moist, Y-tong or plaster nests work well. Connect this to a spacious foraging arena where you can provide fresh plant material daily. Use a water test tube for drinking water. Because they are nocturnal and sensitive to light, keep the setup in a dim area or provide hiding spots. Apply Fluon or similar barrier to the rim of the foraging arena to prevent escapes. Young colonies nest superficially compared to other leafcutters, with fungus chambers only 11-20 cm deep and 0.5-1.5 liters in volume ^[16].

Feeding and the Fungus Garden

These ants are obligate fungus farmers, they cannot survive without their symbiotic fungus Leucoagaricus gongylophorus. Provide fresh leaf material daily from pesticide-free plants. They prefer dicotyledonous plants including rose petals, ligustrum, acalypha, and most broadleaf garden plants ^[21]. Workers will also collect flowers (18% of forage) and fruits (10%) ^[6]. Remove uneaten material after 24-48 hours to prevent mold. The workers macerate fungal staphylae and feed them to larvae, adults consume liquids from the fungus ^[22]. Never feed sugar water or protein, they obtain all nutrition from the fungus garden.

Temperature and Seasonal Care

Maintain temperatures around 25°C for optimal colony health ^[9][23]. These are tropical ants and will become inactive below 10°C ^[8]. Avoid placing nests near air conditioning vents or cold windows. Higher temperatures within safe limits increase activity and foraging. Humidity should be maintained at 70-80%, the fungus garden is sensitive to drying out ^[9]. Mist the nest area occasionally and ensure the water tube is always filled. Unlike temperate species, they do not require hibernation or winter cooling.

Colony Growth and Development

Understanding the life cycle helps with expectations. After nuptial flights in November-December, queens dig founding chambers and deposit a pellet of symbiotic fungus from their infrabuccal cavity ^[24][15]. About 45% of queens die in the first two weeks, often because they fail to establish the fungus. Queens that successfully regurgitate fungus have approximately 30% survival to first workers ^[15]. Eggs appear in week 1,larvae in week 3,pupae in weeks 6-7,and first workers around week 9. The first generation typically has only 2 workers. Growth is slow initially, a colony may take 6-12 months to reach 100 workers. Colonies can eventually grow to several thousand workers over several years ^[14].

Behavior and Division of Labor

A. subterraneus shows remarkable task partitioning based on worker size. Minor workers (0.7-0.8 mm head capsule) perform brood and fungus care, while media and major workers (1.2-2.0 mm) handle foraging and cutting ^[17]. This division is flexible, workers can switch tasks as needed. Foraging is primarily nocturnal, peaking between 8pm-2am ^[6]. On longer trails (over 10 m), cutters frequently transfer fragments to carriers in relay fashion, while on short trails (1 m), cutters carry directly to the nest ^[11]. Workers also show delayed rejection, they may initially accept unsuitable plant material but later discard it once the fungus proves incompatible ^[25].

Common Problems

The biggest threat is fungus garden failure. This can happen from improper humidity (too dry or too wet), contaminated plant material (pesticides, mold), or pathogen introduction. Signs of trouble include workers discarding fungus, reduced foraging, or fungus turning dark. The parasitoid wasp Szelenyiopria talitae can attack larvae, look for dark spots inside larvae indicating developing wasps. Infected colonies usually collapse within 2-3 months ^[26]. Queen founding has very high mortality, this is normal but frustrating. Also watch for escape attempts and ensure barriers are applied. Avoid using imidacloprid or other neonicotinoids near the colony as these chemicals inhibit their grooming defenses and increase susceptibility to entomopathogenic fungi ^[27][23].

Frequently Asked Questions

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References