Acanthostichus longinodis

Acanthostichus longinodis

Acanthostichus longinodis is a tiny, rarely encountered ant species from the Dorylinae subfamily (army ants). Workers measure approximately 3-4mm in total length with a distinctive elongated petiole that gives them their species name (Latin: longus=nodis=swelling). They have a rusty ferrugineous red coloration with smooth, glossy body surfaces and moderately erect hairs. This species is known only from the Chaco region of Paraguay and northern Argentina, where specimens have been collected under stones in semi-arid tropical habitats. The genus Acanthostichus contains around 30 species, all of which are predatory army ants, though specific biology for A. longinodis remains completely undocumented.

Quick Summary

• Difficulty: Unknown, species is extremely rare in antkeeping with no established husbandry information
• Origin & Habitat: Chaco region of Paraguay and northern Argentina. Specimens collected from under stones in semi-arid tropical habitats^[1].
• Colony Type: Unconfirmed, colony structure has not been documented. Based on genus placement in Dorylinae, likely forms small to moderate colonies typical of army ants.
• Size & Growth:
  • Queen: Unknown, only worker specimens have been described
  • Worker: Workers approximately 3-4mm total length, head length 0.76-0.78mm, Weber's length 1.08-1.14mm
  • Colony: Unknown, no colony data exists
  • Growth: Unknown
  • Development: Unconfirmed, no development data exists for this species (Based on related Dorylinae species, development likely takes 4-8 weeks at optimal temperature but this is purely estimated)
• Antkeeping:
  • Temperature: Likely 22-28°C based on subtropical Chaco origin, start in this range and observe colony activity
  • Humidity: Moderate, semi-arid region suggests they prefer drier conditions than many tropical ants. Allow substrate to dry partially between waterings.
  • Diapause: Unknown, no seasonal data available for this species
  • Nesting: In nature found under stones. Likely nests in soil or small cavities. Test tubes or small acrylic nests would be appropriate starting points. Provide some dry areas alongside moist zones.
• Behavior: Behavior is unconfirmed. As a Dorylinae member, likely predatory on other small invertebrates. Army ants typically forage in columns and are aggressive hunters. Escape prevention should be moderate, workers are small but not among the tiniest ants. No documented sting severity.
• Common Issues: This species is virtually unknown in antkeeping, no established husbandry guidelines exist, No queen has ever been described, founding behavior is completely unconfirmed, Colony size and growth rate are unknown, making care difficult to optimize, Wild-caught colonies may be extremely difficult to locate and may have parasites, The entire genus Acanthostichus is rarely kept, so no community experience exists to draw from

Species Discovery and Rarity

Acanthostichus longinodis was only described in 2004 by William Mackay, making it one of the most recently described ant species. The entire type series consists of just three worker specimens collected in Paraguay's Chaco region. This species remains one of the rarest in the antkeeping hobby, with virtually no information available about its colony structure, queen biology, or captive care requirements. The distinctive elongated petiole (petiolar index 150-153) sets this species apart from all other known Acanthostichus species. ^[1]

Identification and Distinguishing Features

This species can be identified by its greatly elongated petiole, which is nearly 1.5 times longer than wide (petiolar index 150-153). The petiole sides form a sharp angle with the dorsal surface, nearly forming a carina. Other distinctive features include the incrassate (thickened) posterior femur and tiny eyes apparently composed of only three ommatidia. The body is smooth and glossy with a ferrugineous red coloration, and the appendages and gaster are slightly lighter in color. These features distinguish it from other South American Acanthostichus species and the two Mexican species with elongate petioles (A. quirozi and A. skwarrae). ^[1]

Habitat and Distribution

Acanthostichus longinodis is known from the Gran Chaco region of Paraguay, specifically the Parque Nacional Defensores del Chaco. The type locality at Cerro León features 'zona pelada' (bare zone) habitat. A recent record extends the known range into Mato Grosso do Sul, Brazil ^[1]. The Chaco is a large tropical/subtropical dry forest region covering parts of Paraguay, Bolivia, and Argentina. The species has been collected under stones, suggesting it nests in soil or under ground-level cover rather than in vegetation. The semi-arid nature of this region suggests this species is adapted to drier conditions than many other Dorylinae^[1].

Taxonomy and Relationships

Acanthostichus belongs to the subfamily Dorylinae, the army ants. This subfamily is known for predatory lifestyles and colony structures ranging from small to very large. However, Acanthostichus species are generally less studied than other Dorylinae genera. The genus contains approximately 30 species distributed primarily in the Americas, with the highest diversity in South America. A 2016 generic revision by Borowiec placed Acanthostichus firmly within Dorylinae based on morphological analysis. Unlike many army ants, Acanthostichus species are not known for the massive colony sizes or nomadic hunting patterns typical of some Dorylinae.

Frequently Asked Questions

References