Pseudomyrmex acanthobius

Pseudomyrmex acanthobius

Pseudomyrmex acanthobius is a slender, elongated ant belonging to the subfamily Pseudomyrmecinae. Workers are typically around 4-5mm with a distinctive long, narrow body shape typical of this genus. The species is native to the Neotropical region, found across Argentina, Bolivia, Brazil, and Paraguay ^[1]. These ants are arboreal by nature, they nest in hollow twigs and branches of trees like Vachellia caven (aromita) in the Chaco region ^[2]. Unlike many ants that forage on the ground, this species is primarily a tree-dwelling ant that forages in the canopy and visits extrafloral nectaries for sugar sources ^[3].

What makes P. acanthobius interesting is its guild classification as an 'agile pseudomyrmecine', these are generalist predators that actively hunt small invertebrates in vegetation, and they have a mutualistic relationship with plants by visiting extrafloral nectaries ^[3]. They are classified as Tropical Climate Specialists, meaning they prefer warm, humid conditions similar to their native rainforest and forest-edge habitats ^[4]. Their very low abundance in ground surveys confirms they are predominantly arboreal ^[5][3].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Neotropical region, Argentina, Bolivia, Brazil, and Paraguay. Found in diverse habitats including veredas (Brazilian wetlands), Chaco woodland, and Caatinga (dry thorn forest). These are arboreal ants that nest in tree hollows, particularly in Vachellia caven (aromita) trees ^[2][3].
• Colony Type: Colony structure is not well documented in research. Based on genus patterns, Pseudomyrmex species typically have single-queen (monogyne) colonies, but this specific species' founding behavior is unconfirmed.
• Size & Growth:
  • Queen: Estimated 6-8mm based on genus typical size, no species-specific measurement found
  • Worker: Approximately 4-5mm based on genus morphology ^[1]
  • Colony: Likely small to moderate colonies, Pseudomyrmex colonies are typically smaller than ground-nesting ants, possibly under 500 workers
  • Growth: Moderate, estimated based on tropical arboreal ant patterns
  • Development: Estimated 6-8 weeks at tropical temperatures (25-28°C) based on related Pseudomyrmex species development (Development time is estimated, no specific study found for this species. Tropical species typically develop faster than temperate ones.)
• Antkeeping:
  • Temperature: Keep at 24-28°C. As a tropical species from northern Argentina and Brazil, they need warm conditions year-round. A small heating cable on one side of the nest creates a temperature gradient ^[3][4].
  • Humidity: Moderate to high humidity (60-80%). These ants come from humid tropical and subtropical regions. Keep the nest substrate slightly moist but ensure ventilation to prevent mold. Their arboreal nature means they tolerate some drying better than fully ground-nesting species.
  • Diapause: No, as a tropical species, they do not require hibernation. Keep them at stable warm temperatures year-round ^[3].
  • Nesting: Arboreal setup is essential. These ants nest in hollow twigs and branches in nature. In captivity, use a naturalistic setup with twigs/branches, or a Y-tong/plaster nest with narrow chambers. Avoid deep soil nests, they prefer above-ground nesting structures. Provide climbing materials and branches reaching up to the nest ^[2][3].
• Behavior: These ants are active foragers that hunt small prey in vegetation. They are generalist predators feeding on small insects and arthropods, and they also visit extrafloral nectaries for sugar ^[3]. Workers are agile and can move quickly, typical of the 'agile pseudomyrmecine' guild. They are not particularly aggressive toward keepers but will defend their nest. Escape risk is moderate, they are small but not as tiny as some myrmicines, though excellent escape prevention is still recommended. They are primarily nocturnal or crepuscular foragers in the wild, though activity patterns in captivity may vary.
• Common Issues: arboreal nature means standard test tube setups often fail, they need climbing structures and above-ground nesting, very low capture rate in studies suggests they are sensitive to disturbance and may be difficult to establish in captivity, tropical temperature requirements mean they cannot tolerate cool temperatures, keep warm year-round, predatory diet means they need regular protein (live small insects), sugar alone is insufficient, captive colonies may be difficult to source as they are not commonly kept in the hobby

Natural History and Distribution

Pseudomyrmex acanthobius is found across the Neotropical region, including Argentina (Corrientes and Misiones provinces), Bolivia, Brazil, and Paraguay ^[1][4]. This species inhabits diverse environments from Brazilian veredas (wetlands) to the dry Chaco woodland and Caatinga thorn forest ^[6][5]. The key to their distribution is the presence of suitable nesting trees, they are obligate arboreal nesters, found nesting specifically in Vachellia caven (aromita) trees in the Chaco Brasileiro ^[2].

Studies show these ants are classified as Tropical Climate Specialists (TCS), indicating they prefer warm, humid conditions ^[4]. Their very low abundance in ground pitfall traps (only 1-7 individuals across multiple studies) confirms they are predominantly arboreal, nesting and foraging in the canopy rather than on the forest floor ^[5][3]. In the Caatinga study, they were actually captured exclusively in the dry season, suggesting they may have seasonal activity patterns tied to rainfall ^[3].

Nest Preferences and Housing

This is an arboreal species that requires above-ground nesting structures. In nature, they nest in hollow twigs and branches of trees, particularly Vachellia caven ^[2]. For captive care, you should replicate this with a naturalistic setup featuring twigs, branches, or cork bark arranged vertically. A Y-tong (acrylic) nest with narrow chambers can work, but you must provide climbing branches reaching to the nest entrance.

Avoid deep soil formicariums, these ants will not use them. Instead, use setups that mimic their natural tree-nesting habitat. Provide multiple small chambers connected by tunnels, scaled to their 4-5mm worker size. Include live or artificial plant material for them to forage on. The nest should be positioned above the foraging area, allowing workers to travel up and down between nest and food sources.

Feeding and Diet

Pseudomyrmex acanthobius is classified as a generalist predator, they actively hunt small invertebrates in vegetation ^[3]. In captivity, offer small live prey such as fruit flies, pinhead crickets, small mealworms, and other tiny insects. Feed protein 2-3 times per week, removing uneaten prey after 24 hours.

As visitors of extrafloral nectaries in the wild, they also accept sugar sources ^[3]. Offer sugar water, honey, or diluted honey water as a constant sugar source. Provide this in a shallow container or cotton wick to prevent drowning. A balanced diet of protein prey plus sugar water works best for maintaining healthy colonies.

Temperature and Seasonal Care

As a tropical species from northern Argentina, Bolivia, Brazil, and Paraguay, P. acanthobius requires warm temperatures year-round. Maintain nest temperatures between 24-28°C ^[3][4]. Room temperature may be sufficient if your home stays in this range, otherwise use a small heating cable on one side of the nest to create a gentle gradient.

Unlike temperate species, these ants do not require hibernation or winter cooling. Keep them at stable warm temperatures throughout the year. Sudden temperature drops can stress or kill colonies. Monitor with a thermometer placed near the nest. The species has been found in both wet and dry seasons across its range, suggesting they can handle some humidity variation but prefer consistent warmth ^[5][3].

Behavior and Temperament

These ants belong to the 'agile pseudomyrmecine' guild, meaning they are active, quick-moving foragers that hunt prey in vegetation ^[3]. Workers are slender and fast, capable of moving quickly across branches and leaves. They are not typically aggressive toward humans but will defend their nest if threatened.

Their arboreal lifestyle means they spend considerable time climbing. Provide vertical space and climbing materials in their enclosure. Workers will venture out to forage and then return to the nest. They are primarily active during warmer hours but may show peak activity at different times depending on your specific conditions. Observe your colony to determine their peak activity periods for feeding.

Frequently Asked Questions

References