Yunodorylus eguchii

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Vietnam (Dong Nai Province, Tay Ninh Province) in lowland evergreen/semi-evergreen forest and dwarf forest at 5-160m altitude ^[1][3]
• Colony Type: Monogyne, single queen colonies with one reproductive queen ^[2]. Queens are subdichthadiigyne (intermediate form between worker and full dichthadiiform), with weaker dimorphism than typical army ants ^[3].
• Size & Growth:
  • Queen: Size data unavailable, known only from head measurements
  • Worker: Size data unavailable, workers are polymorphic with head width ranging 0.50-0.76mm ^[1][2]. Exact body length not recorded.
  • Colony: Several thousand workers in mature colonies ^[2]
  • Growth: Moderate, total development 9-10 weeks from egg to worker ^[2]
  • Development: 9-10 weeks (63-73 days) at room temperature ^[2] (Egg stage: 16-19 days, larval stage: 24-26 days, cocoon stage: 27-28 days ^[2]. Phasic reproduction means eggs are laid in batches rather than continuously.)
• Antkeeping:
  • Temperature: Tropical species, inferred from natural habitat in lowland Vietnam. Keep at 24-28°C for optimal growth ^[1][3].
  • Humidity: Moderate to high, they nest in soil and have been found in both humid lowland forest and drier dwarf forest ^[1]. Keep substrate moist but not waterlogged.
  • Diapause: No, as a tropical species, they do not require hibernation. They may show reduced activity during cooler periods but no true diapause ^[2].
  • Nesting: Soil-nesting species. In captivity, they do well in naturalistic setups with moist substrate or plaster nests. They have been found in the walls of termite mounds in the wild ^[3]. Provide deep substrate (at least 5cm) for nesting. Also recorded under stones ^[1].
• Behavior: Predatory ants that actively hunt other insects. Workers forage individually or follow trails of other workers. When they find prey, they sting it and recruit nearby nestmates to help subdue it ^[2]. They have a functional stinger and will use it defensively. Workers are moderately aggressive when defending their colony. Escape prevention is important due to their very small size, they can slip through small gaps easily.
• Common Issues: tiny size means escapes are likely without fine mesh barriers and sealed connections, predatory diet requires live prey, they may reject some foods like Drosophila or crickets unless immobilized ^[2], phasic reproduction means colony growth is cyclical, not continuous, expect pauses between brood batches, queen can die during physogastric period, documented in lab colonies ^[2], workers do not lay eggs if queen is lost, meaning orphaned colonies cannot recover ^[2]

Housing and Nest Setup

Yunodorylus eguchii is a soil-nesting ant that does well in naturalistic setups with deep, moist substrate. In the wild, they nest in soil under stones and have been found in the walls of termite mounds ^[1][3]. For captivity, use a setup with at least 5-8cm of moist soil or a plaster nest with a water reservoir to maintain humidity. Because these ants are very small (body size not officially recorded but head width under 0.8mm), escape prevention is critical, use fine mesh on any openings and ensure all connections are sealed. A formicarium with a foraging area connected to a nest chamber works well. They prefer darkness for nesting, so cover the nest portion with a dark cloth or use a nesting box with a cover.

Feeding and Diet

This is a predatory ant that primarily hunts other insects. In laboratory tests, they accepted 100% of ant brood presented to them, including species like Camponotus, Lasius, Myrmica, Pheidole, and Tetramorium ^[2]. They also readily accepted termites, small mealworms, and dermapteran eggs. However, they rejected Drosophila larvae, crickets, centipedes, isopods, and springtails ^[2]. Cockroaches and crickets were only accepted after artificial immobilization. For captive feeding, offer small live insects such as fruit flies, pinhead crickets, and ant brood from feeder colonies. They also accept small pieces of mealworm or other soft-bodied insects. Feed protein 2-3 times per week, and remove uneaten prey after 24 hours to prevent mold.

Temperature and Seasonal Care

As a tropical species from Vietnam, Yunodorylus eguchii requires warm temperatures. Keep the nest area at 24-28°C for optimal brood development. At this temperature range, development from egg to worker takes about 9-10 weeks ^[2]. They do not require hibernation or diapause, this is a year-round active species. However, avoid temperatures above 30°C as this can stress the colony. A heating cable on one side of the nest can create a temperature gradient, allowing the ants to self-regulate. Room temperature in most homes (20-24°C) may slow development but should be survivable. Monitor colony activity, if workers seem sluggish, increase temperature slightly.

Colony Structure and Reproduction

Yunodorylus eguchii forms monogyne colonies with a single queen. The queen is a subdichthadiigyne, an intermediate form between a worker and the fully developed dichthadiiform queens seen in true army ants. This means the queen is larger than workers but not dramatically so, and she retains some worker-like features ^[3]. Colonies in the wild contain several thousand workers ^[2]. The species exhibits phasic reproduction, queens go through cycles of physogastry (abdominal swelling) followed by egg-laying, rather than laying eggs continuously. In lab colonies, the reproductive cycle took 56-63 days ^[2]. Workers are polymorphic, varying considerably in size, with the largest workers having head widths about 1.5 times larger than the smallest ^[2]. Workers do not lay eggs if the queen is lost, meaning orphaned colonies cannot replace her ^[2].

Foraging Behavior

Unlike true army ants that form massive raiding columns, Yunodorylus eguchii forages in a more modest fashion. Workers either walk along the trails of other foragers or search alone ^[2]. When a forager encounters prey, it grabs the prey, bends its abdomen to sting it, and then surrounding workers converge to help subdue and transport the prey back to the nest. Notably, no conspicuous trail-laying behavior (like pheromone marking) was observed, the ants simply follow each other ^[2]. In laboratory colonies, sometimes almost half of the entire colony was actively foraging, with forager numbers matching the number of larvae present. This suggests they are opportunistic foragers that can mobilize many workers when food is available.

Defense and Stinging

As a member of the Dorylinae subfamily, Yunodorylus eguchii has a functional stinger. Workers will use it defensively when the colony is threatened ^[2]. The sting is primarily used for subduing prey, workers grab prey with their mandibles, then sting it to immobilize it with venom before recruiting help from nestmates ^[2]. The venom is effective against other insects, including a wide range of ant species. For antkeepers, this means the ants can sting if handled roughly or if the nest is disturbed. The sting is not dangerous to humans but may cause mild irritation. Always handle these ants gently and avoid disturbing their nest unnecessarily.

Frequently Asked Questions

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References