Yunodorylus eguchii

Yunodorylus eguchii

Yunodorylus eguchii is a small predatory ant from the Dorylinae subfamily native to Vietnam. Workers measure 0.50-0.76mm and are polymorphic, meaning they come in noticeably different sizes within the same colony ^[1]. The species has a distinctive bicolored pattern: large workers have a light chestnut-brown head and mesosoma while the abdomen is yellowish-brown, with smaller workers being lighter overall ^[1]. This is a non-army doryline ant, unlike true army ants, they don't form massive raiding swarms but instead forage individually or in small groups along established trails ^[2]. The genus Yunodorylus contains just four named species found in Vietnam and surrounding regions, making this a relatively rare and unusual ant in the antkeeping hobby ^[3].

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].
  • Colony: Monogyne
• Size & Growth:
  • Queen: Head width 0.826-0.876mm ^[2], estimated 4-5mm total length
  • Worker: 0.50-0.76mm head width (HW), polymorphic ^[1]
  • 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, keep at 24-28°C. They come from lowland Vietnam where temperatures are warm year-round ^[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 soil walls of termite mounds in the wild ^[3]. Provide deep substrate (at least 5cm) for nesting.
• 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 small size, they can slip through small gaps easily.
• Common Issues: small size means escapes are likely without fine mesh barriers, predatory diet requires live prey, they may reject some foods, phasic reproduction means colony growth is cyclical, not continuous, colonies may fail if not provided adequate protein sources, queen can die during physogastric period, documented in lab colonies ^[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 and have been found in the walls of termite mounds ^[3]. For captivity, use a naturalistic setup with at least 5-8cm of moist soil or a plaster nest with a water reservoir to maintain humidity. Because they are small (under 1mm), 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 an acrylic nest 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 like 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 being about 1.5 times larger than the smallest ^[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

References