Pseudomyrmex tenuis

Pseudomyrmex tenuis

Pseudomyrmex tenuis is a very small, slender ant native to the Neotropical region, ranging from southern Mexico down through Central America and into South America as far as Argentina ^[1]. Workers measure just 0.48-0.53mm in head width with an unusually elongated head, giving them a distinctive 'twig-like' appearance ^[2]. They are concolorous testaceous brown with large elongate eyes, a sharply margined pronotum, and a tall, thin, pointed petiole ^[1]. This species belongs to the P. tenuis group and represents a basal lineage within the genus Pseudomyrmex ^[3].

Unlike many arboreal ants, P. tenuis is a generalist twig-nester that can nest in both vegetation and occasionally in fallen trunks ^[4]. They are diurnal and highly agile, patrolling large areas around their nests solitarily while orienting by vision ^[4]. They function as predators on vegetation and visitors of extrafloral nectaries, making them an interesting species for keepers interested in observing active, visual-oriented foraging behavior.

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Neotropical region, found in Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guyana, Peru, and Suriname ^[1]. Inhabits tropical dry forests, rainforests, cloud forests, and transitional areas between Amazon and Cerrado biomes ^[5][6]. Typically nests in dry twigs in vegetation but can also use fallen trunks ^[4][7].
• Colony Type: Colony structure is unconfirmed. Pseudomyrmex species typically have single-queen colonies, but specific data for P. tenuis is lacking.
• Size & Growth:
  • Queen: Unconfirmed, no specific measurements found in research data
  • Worker: Very small: HW 0.48-0.53mm, head index CI 0.56-0.62 ^[2]
  • Colony: Estimated moderate, Pseudomyrmex colonies typically reach several hundred workers
  • Growth: Moderate, based on typical Pseudomyrmex development patterns
  • Development: Estimated 6-10 weeks at tropical temperatures based on genus-level data (Development time is inferred from related Pseudomyrmex species, no species-specific data available)
• Antkeeping:
  • Temperature: Keep at 24-28°C, this is a tropical species requiring warm conditions ^[5]. Provide a temperature gradient allowing workers to self-regulate.
  • Humidity: Moderate humidity around 60-80%. These ants inhabit tropical forests and forest edges, so the nest area should be kept slightly moist but not waterlogged.
  • Diapause: No, as a tropical species, P. tenuis does not require hibernation. They remain active year-round in consistent tropical conditions.
  • Nesting: Use a naturalistic setup with small twigs or bamboo sections, or a small acrylic/plaster nest with narrow chambers scaled to their tiny size. They are twig-nesters by nature and appreciate vertical space for climbing ^[4].
• Behavior: P. tenuis is a diurnal, highly active species that orients by vision and patrols large areas around the nest solitarily ^[4]. They are agile foragers and can act as predators on small arthropods and visitors of extrafloral nectaries. Workers are small but fast-moving. Escape prevention should be excellent due to their tiny size, they can easily slip through small gaps. They are not particularly aggressive toward keepers but will defend their nest if threatened.
• Common Issues: escape prevention is critical, their very small size means they can squeeze through tiny gaps, tropical temperature requirements mean they cannot tolerate cool conditions, keep warm year-round, wild-caught colonies may harbor parasites that can cause colony failure in captivity, small colony size means slower population growth, patience is required, dry conditions can cause stress, maintain adequate humidity without saturating the nest

Natural History and Distribution

Pseudomyrmex tenuis is widely distributed across the Neotropics, from southern Mexico through Central America (Costa Rica) and down into South America including Brazil, Colombia, Peru, Bolivia, Argentina, and the Guianas ^[1][5]. This species has been recorded in multiple habitat types including tropical dry forests, rainforests, cloud forests, and transitional areas between the Amazon and Cerrado biomes ^[6][5]. They are considered a common species in Amazonian floodplain forests, recorded at numerous sites across hundreds of kilometers of study areas ^[8]. In Colombia, they are found in departments including Antioquia, Caquetá, Cundinamarca, Meta, and others at various altitudes ^[9][2]. The species is associated with Witheringia plants and is a generalist twig-nester, nesting in dead twigs and small cavities in vegetation ^[10].

Housing and Nest Setup

In captivity, P. tenuis does well in small naturalistic setups that mimic their natural twig-nesting behavior. Provide small bamboo sections, twigs, or a scaled acrylic/plaster nest with narrow chambers appropriate for their tiny size. They are arboreal by nature and appreciate vertical space for climbing ^[4]. A test tube setup can work for founding colonies, but they will benefit from moving to a more naturalistic formicarium as the colony grows. Because of their very small size, escape prevention must be excellent, use fine mesh barriers and ensure all connections are sealed tightly. They are diurnal and visually oriented, so some visibility into the nest chambers helps you observe their activity ^[4].

Feeding and Diet

P. tenuis is a predator and omnivore in nature, acting as a predator on vegetation-dwelling arthropods and visiting extrafloral nectaries for sugary secretions ^[4][11]. In captivity, offer small live prey such as fruit flies, pinhead crickets, and other tiny arthropods. They should also have access to sugar sources, a drop of honey water or sugar water will be readily accepted. Feed small amounts of protein prey 2-3 times per week, and keep a sugar source available at all times. Remove uneaten prey after 24-48 hours to prevent mold. Their small size means even tiny prey items are appropriate, focus on offering appropriately sized insects rather than large prey items.

Temperature and Seasonal Care

As a tropical species, P. tenuis requires warm temperatures year-round. Keep the nest area at 24-28°C, with a slight gradient allowing workers to self-regulate if needed ^[5]. This species does not require hibernation or diapause, they remain active throughout the year in consistent tropical conditions. Avoid temperatures below 20°C, as prolonged cool exposure can weaken or kill the colony. A small heating cable or mat on one side of the nest can help maintain appropriate temperatures, but always provide an unheated area so ants can escape excessive heat. Room temperature within the range is acceptable in most homes.

Behavior and Observation

One of the most interesting aspects of P. tenuis is their diurnal, visually-oriented foraging behavior. Unlike many ants that rely primarily on chemical trails, these ants patrol large areas around their nests solitarily and navigate using their excellent vision ^[4]. They are highly agile and quick-moving, making them entertaining to watch. Workers will venture out to forage and can travel significant distances from the nest in search of prey and nectar. This species is not particularly aggressive but will defend the nest if threatened. Their small size and active nature make them best suited for observation-focused setups where you can watch their foraging patrols.

Frequently Asked Questions

References