Solenopsis macdonaghi

Solenopsis macdonaghi

Solenopsis macdonaghi is a medium-sized fire ant species native to the floodplains of eastern Argentina and western Uruguay, with records in Paraguay ^[1]. Workers are red-yellow to brown-yellow with a distinctive dark brown gaster (the rear body section), while queens range from orange to dark orange ^[1]. This species belongs to the Solenopsis saevissima species group, which includes some of the most well-studied fire ants in the world. What makes S. macdonaghi particularly interesting is its social polymorphism, colonies can have either a single queen or multiple queens working together, controlled by a specific gene variant ^[2]. This flexibility in social organization is rare among ants and makes them fascinating to observe.

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to the floodplains of eastern Argentina and western Uruguay, with records in Paraguay. Found in gallery forest edges and campo cerrado (open savanna) habitats ^[1][3].
• Colony Type: Socially polymorphic, colonies can be either monogyne (single queen) or polygyne (multiple queens). The presence of b-like alleles in polygyne colonies indicates genetic control of this trait ^[2][4].
  • Colony: Optionally polygyne
  • Founding: Claustral
• Size & Growth:
  • Queen: 6.9-7.5 mm ^[1]
  • Worker: Major workers are among the largest in the species group, along with S. megergates and S. quinquecuspis ^[5]
  • Colony: Colony size data not specifically documented, but related fire ants typically reach tens of thousands of workers
  • Growth: Moderate, inferred from related fire ant species
  • Development: Estimated 5-7 weeks at optimal temperature based on related Solenopsis species (Fire ant development is temperature-dependent, warmer conditions accelerate development)
• Antkeeping:
  • Temperature: Keep at 24-28°C. Fire ants prefer warm conditions, similar to their subtropical native habitat. A heating cable on one side of the nest creates a suitable gradient.
  • Humidity: Moderate humidity around 50-60%. Fire ants prefer drier conditions compared to many tropical ants. Allow the nest substrate to dry slightly between waterings.
  • Diapause: No strong diapause required given their subtropical origin, but a slight cool period (15-18°C) during winter months may benefit colonies
  • Nesting: Use a dry nest setup. Fire ants prefer well-drained conditions. Y-tong (AAC) nests or test tube setups work well. Avoid overly humid or wet conditions.
• Behavior: Fire ants are defensive and will sting when threatened. Workers are aggressive foragers and will readily defend their nest. They have a potent sting that can cause painful welts in humans, handle with caution. Escape prevention is important as they are active and will explore for exits. They are omnivorous, accepting both protein foods and sugar sources.
• Common Issues: sting hazard, these ants can deliver painful stings, so handle with care and use proper protection, escape artists, active foragers that will find and exploit any gaps in their enclosure, pathogen susceptibility, wild colonies can carry microsporidian parasites like Vairimorpha invictae and Thelohania solenopsae ^[6][7], social structure confusion, colonies may be monogyne or polygyne, which affects how you house multiple queens

Housing and Nest Setup

Solenopsis macdonaghi does well in standard ant keeping setups. Test tubes work well for founding colonies, fill the tube one-third with water stopped by a cotton ball, providing a humid chamber for the queen. For established colonies, Y-tong (AAC) nests or acrylic formicaria work nicely. Fire ants prefer drier conditions than many ants, so avoid setups that retain excessive moisture. Ensure excellent escape prevention, these ants are persistent explorers and will find any gap. Apply fluon or similar barriers to the rim of the outworld. Provide a shallow water station and protein food in the outworld area. ^[1]

Feeding and Diet

Fire ants are omnivorous and accept a wide variety of foods. Offer protein sources like mealworms, crickets, or other small insects 2-3 times per week. They also readily accept sugar sources, honey water, sugar water, or commercial ant nectar. For enrichment, you can occasionally offer small pieces of fruit. In the wild, they forage for seeds, insects, and honeydew from aphids. Remove uneaten protein within 24-48 hours to prevent mold. A constant sugar water or honey supply is recommended for established colonies.

Temperature and Seasonal Care

Keep your colony at 24-28°C for optimal growth and brood development. Fire ants are adapted to warm subtropical conditions and thrive in heated setups. A small heating cable placed under or on one side of the nest creates a temperature gradient that ants can choose between. During winter, you can reduce temperatures slightly to 18-22°C, but avoid cold hibernation as they're not adapted to freezing conditions. A slight cool period may simulate their natural seasonal cycle, but is not strictly required. Monitor colony activity, if workers become sluggish, slightly increase temperature.

Defense and Sting Hazard

Solenopsis macdonaghi has a potent sting and should be handled with extreme caution. Unlike some ants that merely bite or spray formic acid, fire ants deliver a painful venom that causes burning sensation and raised welts. When working with these ants, always use protective gear including gloves and eye protection. Never handle them without proper preparation. If stung, wash the area with soap and water and apply a cold compress. Those with insect venom allergies should avoid keeping this species entirely. The sting risk makes them unsuitable for beginners who want to handle their ants frequently. ^[1]

Health and Pathogens

Wild-caught colonies of S. macdonaghi can carry several pathogens that affect fire ants. The microsporidian parasites Vairimorpha invictae and Thelohania solenopsae have been documented infecting this species in its native range ^[6][7]. These pathogens can spread to other ant colonies and may eventually kill your colony. If collecting from the wild, quarantine new colonies and monitor for signs of illness, workers appearing sluggish, unusual mortality, or colony decline. Purchasing from reputable breeders who guarantee disease-free colonies is strongly recommended.

Social Structure and Colony Dynamics

One of the most fascinating aspects of S. macdonaghi is its social polymorphism. Some colonies have a single queen (monogyne), while others have multiple queens (polygyne). This is genetically controlled, polygyne colonies contain specific b-like alleles that enable multiple queens to coexist ^[2][4]. In polygyne colonies, queens may remain in the nest and continue laying eggs while new queens are produced. This flexibility means your colony could develop either structure depending on what queen(s) you started with. The social structure also affects how colonies interact, monogyne colonies are typically more aggressive toward outsiders than polygyne colonies.

Legal and Ethical Considerations

Solenopsis macdonaghi is native to South America and should never be released in North America, Europe, or other regions where it is not native. Related fire ants like S. invicta have become major invasive pests in many parts of the world, causing ecological and economic damage. If you can no longer keep your colony, contact a local ant keeper or entomological society to rehome it. Never dump ants in the wild. Additionally, check your local regulations before acquiring this species, some areas have restrictions on keeping native or non-native fire ants.

Frequently Asked Questions

References