Strumigenys membranifera

Strumigenys membranifera - "Membraniferous Dacetine Ant"

Strumigenys membranifera is a tiny predatory ant measuring just 1.9-2.1mm in worker length ^[1]. Workers have a distinctive appearance with short triangular mandibles, six-segmented antennae ending in a two-segmented club, and a large curtain of spongiform tissue beneath the waist segments ^[2]. Their body coloration ranges from dull yellow to yellowish-brown ^[3]. This species belongs to the tribe Attini within the Myrmicinae subfamily and is the sole member of the Strumigenys membranifera group ^[1]. Originally described from Italy in 1869,it has become one of only three dacetine ant species with truly global distribution, spread entirely through human commerce ^[4].

What makes this species particularly interesting is its reproductive biology. S. membranifera reproduces primarily through thelytokous parthenogenesis, queens produce offspring without mating ^[5]. Females develop from unfertilized eggs, and males are occasionally produced ^[6]. This adaptation seems particularly suited to colonizing disturbed open habitats where finding mates might be difficult. The species also displays remarkable hunting behavior, workers stalk springtails (their primary prey) with extraordinary patience, slowly creeping within striking distance before making a sudden mandibular snap ^[1].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to the Afrotropical region (Ghana, Sierra Leone, South Africa) ^[7]. Now introduced to nearly all biogeographic realms worldwide through human commerce, making it a pantropical tramp species ^[3]. Found in highly disturbed areas like lawns, pastures, gardens, and cultivated fields, typically nesting beneath debris or dead wood on the ground ^[8].
• Colony Type: Colonies reproduce through thelytokous parthenogenesis, queens produce offspring asexually without mating ^[5]. Colony size reaches approximately 250 workers, with documented maximum of 350 individuals ^[7]. Single-queen colonies with asexual reproduction.
  • Colony: Monogyne
  • Founding: Claustral
• Size & Growth:
  • Queen: 0.51-0.53 mm head length,0.44-0.46 mm head width ^[2]
  • Worker: 1.9-2.1 mm total length, head length 0.46-0.50 mm, head width 0.40-0.44 mm ^[9][10]
  • Colony: Approximately 250 workers, up to 350 workers ^[7]
  • Growth: Moderate
  • Development: Approximately 7 weeks (51 days total at 27°C: 13 days egg,19 days larva,19 days pupa) ^[8] (Development times measured at constant 27°C, lower temperatures will extend development)
• Antkeeping:
  • Temperature: Keep at 24-27°C for optimal development. This species tolerates a range from room temperature up to warm tropical conditions. Avoid temperatures below 20°C.
  • Humidity: Moderate humidity preferred. Keep substrate consistently moist but not waterlogged. This species is more adaptable to drier conditions than many other Strumigenys, can tolerate relatively dry, open soil ^[8].
  • Diapause: No true diapause required. As a tropical/tramp species, it remains active year-round if kept warm. However, slight cooling in winter may slow activity.
  • Nesting: Prefers naturalistic setups with moist substrate. Works well in test tube setups or acrylic nests with dirt filling. Provide access to small prey items. Y-tong nests with tight chambers also work, but ensure humidity is maintained.
• Behavior: This is a shy, cryptic species that spends most of its time hunting in the substrate. Workers are slow-moving and freeze when disturbed, they rely on camouflage rather than aggressive defense ^[1]. Despite their small size, they are pugnacious predators that will attack small soft-bodied arthropods with surprising aggression, using their mandibles to seize prey and stinging it into immobility ^[8]. They specialize in hunting springtails (Collembola) but accept a wide range of tiny invertebrates. Escape risk is low, they are tiny and slow, but still use standard escape prevention. Workers do not participate in trophallaxis (food sharing between individuals) ^[8].
• Common Issues: tiny size makes them difficult to house, need fine mesh barriers and tight-fitting lids, prey must be very small, springtails are ideal, other micro-arthropods may be refused, slow growth compared to common ant species, beginners may lose patience, colonies remain small (under 350 workers), not impressive for display, thelytokous reproduction means no males in most colonies, queen replacement is asexual

Housing and Setup

Strumigenys membranifera requires a small, humid enclosure with plenty of substrate for hunting. Test tube setups work well for founding colonies, use a water reservoir with cotton separation, keeping the tube partially filled and the rest as a dry foraging area. For established colonies, a small acrylic nest or naturalistic setup with moist dirt works best. Because they are tiny (under 2mm), escape prevention must be excellent, use fine mesh on any ventilation. The nest should have tight chambers scaled to their small size. Provide a constant water source and keep humidity moderate to high. They rarely forage openly above ground, so most activity happens within the substrate ^[1].

Feeding and Diet

This species is a specialized predator that feeds almost exclusively on tiny soil arthropods, particularly springtails (Collembola) ^[11]. In captivity, offer live springtails as a primary food source, these can be cultured separately or purchased. They will also accept other small soft-bodied prey like micro-arthropods, but generally refuse larger insects. Wilson (1954) documented their wide prey acceptance including japyx and termites, though these were attacked more for nest defense than feeding ^[8]. They do not participate in trophallaxis, so food is not shared between workers or to larvae, each ant consumes prey individually ^[8]. Sugar sources are typically not accepted since they are obligate predators.

Temperature and Seasonal Care

Keep colonies at 24-27°C for optimal development and activity. Development research shows eggs hatch in about 13 days, larvae develop in 19 days, and pupae emerge in 19 days at a constant 27°C ^[8]. Lower temperatures will significantly slow development. As a pantropical tramp species, they do not require true hibernation, maintain warm temperatures year-round. However, they can tolerate brief cooling periods. In their introduced range, colonies have been found in areas with seasonal temperature variation, suggesting some tolerance for cooler conditions. Room temperature (20-24°C) is acceptable but will result in slower growth.

Hunting Behavior

The hunting behavior of S. membranifera is fascinating and unlike most ants. When stalking springtails, workers enter a deliberate 'crouching' posture and move extraordinarily slowly, sometimes taking several minutes to creep within striking distance ^[1]. They freeze when prey moves rapidly, sometimes waiting in ambush position for up to a minute. Workers open their mandibles to about 60° angle and strike suddenly, typically aiming at appendages rather than the body itself. Captured prey often struggles vigorously, but workers are tenacious and will sting them into immobility before releasing ^[1]. This patient hunting style differs dramatically from the rapid, aggressive attacks they display toward larger insects like termites.

Reproduction and Colony Growth

S. membranifera reproduces through thelytokous parthenogenesis, queens produce female offspring (workers and new queens) from unfertilized eggs without mating ^[5]. Males are occasionally produced but rare ^[6]. This reproductive mode is adaptive for tramp species in disturbed habitats where finding mates would be difficult. Alate queens are produced over an extended period, in southeastern US they appear from June through November, while in California they have been recorded in February and late July ^[5]. Colonies reach approximately 250 workers, with documented maxima of 350 ^[7]. Growth is moderate, expect 6-8 weeks from egg to worker at optimal temperature.

Frequently Asked Questions

References