Oxyepoecus plaumanni

Oxyepoecus plaumanni

Oxyepoecus plaumanni is a tiny ant species measuring just 1.9-2.2mm for workers and 2.6-2.7mm for queens. They have a chestnut brown coloration with smooth and shining body surfaces, marked with distinctive longitudinal costulae (grooves) on the head and thorax. Their eyes are remarkably small, with only 5-6 facets in a row. This species belongs to the Solenopsidini tribe and is known only from southern Brazil, specifically the states of Rio Grande doSul, Santa Catarina, and Paraná. All specimens have been collected from leaf-litter in Araucaria forests and evergreen forests, making them a true leaf-litter specialist ^[1][2].

This ant is notable for being extremely habitat-specific, research shows they occur exclusively in primary forest and are never found in secondary growth or modified landscapes like rubber plantations. They live in the top 10cm of soil and leaf-litter, making them a challenging species to locate and study in the wild. Their tiny size and ground-dwelling habits mean they require very specific captive conditions to thrive ^[3][4].

Quick Summary

• Difficulty: Hard
• Origin & Habitat: Southern Brazil (Rio Grande do Sul, Santa Catarina, Paraná states) in Araucaria forests and evergreen forests at elevations of 600-1000m. They live in leaf-litter on the forest floor in primary forest only ^[1][2][3].
• Colony Type: Colony structure is unconfirmed. Males have never been collected, suggesting reproduction may occur through ergatoid (wingless) queens or unverified mating behavior. Known colonies are small based on collection data ^[1][2].
• Size & Growth:
  • Queen: 2.6-2.7mm ^[1]
  • Worker: 1.9-2.2mm ^[1]
  • Colony: Unknown, likely small (under 100 workers typical for this genus based on collection data)
  • Growth: Unknown, likely slow to moderate given small colony sizes
  • Development: Unconfirmed, no direct development data exists. Based on related Solenopsidini species, estimate 6-10 weeks at optimal temperature. (No published development timeline exists for this species. Related tiny myrmicines typically take 6-10 weeks from egg to worker.)
• Antkeeping:
  • Temperature: Keep around 20-24°C. Southern Brazil has mild subtropical to temperate conditions. Avoid temperatures above 28°C, they are adapted to cool, stable forest floor temperatures.
  • Humidity: High humidity required, these are leaf-litter ants from humid forest floors. Keep substrate consistently moist but not waterlogged. Provide a gradient with damp areas and slightly drier spots for the ants to choose.
  • Diapause: Likely required, southern Brazil experiences mild winters (June-August). Reduce temperature to 15-18°C for 2-3 months during this period.
  • Nesting: Y-tong (AAC) nests or small acrylic nests work well given their tiny size. Provide tight chambers and narrow passages scaled to their 2mm body size. Use moist substrate (like soil or plaster) to maintain humidity.
• Behavior: These ants are extremely small and likely shy. They are ground-dwelling leaf-litter specialists that probably forage slowly through the substrate rather than actively hunting on the surface. Their tiny eyes suggest limited visual capability, they likely rely on chemical cues and touch. Escape prevention is critical due to their minute size, they can squeeze through the tiniest gaps. Temperament is likely non-aggressive given their small size and ground-dwelling habits. They are probably nocturnal or active in low-light conditions within the leaf-litter layer ^[1].
• Common Issues: escape prevention is critical, they are extremely tiny (2mm) and can squeeze through the smallest gaps, high humidity requirements are difficult to maintain without causing mold, they are primary forest specialists and may not tolerate captive conditions well, colony size remains small, slow growth can be discouraging, no established captive breeding protocols exist, wild-caught colonies may struggle

Natural History and Distribution

Oxyepoecus plaumanni is one of the most restricted ant species in terms of habitat in southern Brazil. It is known only from the states of Rio Grande do Sul, Santa Catarina, and Paraná, with most specimens collected between 600-1000m elevation. The species was discovered by Fritz Plaumann, a renowned entomologist who collected extensively in southern Brazil during the 1950s-1970s. All known specimens come from Berlesate collections, a method that involves sifting through forest leaf-litter to extract tiny invertebrates. This confirms they are true leaf-litter specialists living in the top 10cm of the forest floor. They inhabit both dense evergreen forests and drier forest types within the Araucaria forest ecosystem. Critically, research shows this species is exclusive to primary forest, it has never been recorded in secondary growth, plantations, or grassland areas ^[1][4][3][2].

Identification and Morphology

Workers measure just 1.9-2.2mm, making them among the smaller ants in the Solenopsidini tribe. They have a distinctive chestnut brown coloration with lighter mandibles, antennae, and legs. The most diagnostic feature is the longitudinal costulae (grooves) on the head between the frontal carinae, these do not reach the vertexal margin or laterally to the compound eyes. Their eyes are remarkably tiny, with only 5-6 facets in the greatest diameter and fewer than 20 total ommatidia. The scape (first antennal segment) fails to reach the occipital corner by a distance greater than its own maximum thickness. The petiole is strongly pedunculate with a high, rounded node that is not compressed. Queens are larger at 2.6-2.7mm and possess three ocelli of equal size. Males have never been collected, which is unusual and suggests either ergatoid reproduction or that males are rarely produced ^[1].

Nest Preferences and Housing

In captivity, these tiny ants require carefully scaled housing. Y-tong (acrylic alloy container) nests or small acrylic formicaria with tight chambers work best. The chambers should be narrow, these are not ants that will use large open spaces. Use moist substrate to maintain high humidity, soil-filled test tubes or plaster nests with water reservoirs work well. Because they are so small, standard test tube setups may be too large, consider using smaller containers or modifying setups to create tight, humid chambers. The nesting material should remain consistently moist but never waterlogged. Given their extreme habitat specificity, providing a naturalistic setup with leaf-litter material may help them feel more at home. Escape prevention must be excellent, these 2mm ants can slip through gaps that seem impossible ^[1][2].

Feeding and Diet

The diet of Oxyepoecus plaumanni has not been directly studied, but based on their tribe placement in Solenopsidini (which includes Solenopsis and other small predatory ants), they likely prey on tiny invertebrates. In captivity, offer small live prey such as springtails, fruit flies, and other micro-arthropods. Given their minute size, even small fruit fly pieces may be too large, consider chopping prey into smaller portions. Sugar sources may be accepted but are not a primary food source for this group. Feed small amounts of protein 2-3 times per week and remove uneaten prey within 24 hours to prevent mold in the humid setup they require. Always provide access to fresh water ^[2].

Temperature and Seasonal Care

These ants come from southern Brazil where temperatures are mild. Keep the nest at 20-24°C, avoiding both extremes. They likely experience a cooler period during southern hemisphere winter (June-August) when temperatures drop in their native habitat. Provide a diapause period of 2-3 months at 15-18°C during winter months. Avoid temperatures above 28°C, these are cool-adapted forest floor ants that do not tolerate heat well. Use a heating cable on one side of the nest only if room temperature falls below their requirements, and always provide a temperature gradient so ants can move to cooler areas if needed. Place heating on top of the nest, not underneath, to avoid evaporating moisture too quickly.

Challenges and Common Problems

This species presents significant challenges for antkeepers. First, they are extremely habitat-specific, research confirms they only survive in primary forest conditions, suggesting they may be sensitive to captive environments. Second, their tiny size makes escape prevention critical and housing difficult. Third, no established captive breeding protocols exist, and wild-caught colonies may struggle in captivity. Fourth, their humidity requirements create a constant battle against mold. Fifth, colony growth appears to be slow based on collection data, which can be discouraging. Finally, the complete lack of information on their founding behavior and colony structure means keepers are essentially working with unverified assumptions. This species is best suited for experienced antkeepers who can maintain precise humidity and temperature conditions ^[3][4].

Frequently Asked Questions

References