Polyergus bicolor

Polyergus bicolor - "Bicolored Amazon Ant"

Polyergus bicolor is a small to medium-sized dulotic ant native to the upper Mississippi Valley, ranging from the western Great Lakes region west to the Dakotas and southern Manitoba. Workers measure 4.8-6.6mm with a distinctive two-tone appearance: the head and mesosoma are a dull red while the gaster is nearly black. This species is easily distinguished from other North American Polyergus by its bicolored pattern and sparse pilosity, notably lacking any erect hairs on the vertex and having only 0-2 setae on the pronotum ^[1].

This is a slave-making (dulotic) ant that cannot survive without a host colony. Unlike typical ants that build their own nests and forage for food, Polyergus bicolor queens invade colonies of Formica ants (primarily Formica subaenescens, occasionally Formica neorufibarbis), kill the host queen, and trick the host workers into raising their brood. The host workers do all the nest work while the Polyergus workers focus on raiding other Formica colonies to steal more pupae ^[2].

Quick Summary

• Difficulty: Expert
• Origin & Habitat: Upper Mississippi Valley region, western Great Lakes to the Dakotas and southern Manitoba. Nests in rotting logs and fallen limbs in moist forest habitats, often near tamarack bogs ^[2][3].
• Colony Type: Dulotic (slave-making), requires a host Formica colony to survive. The Polyergus queen invades and kills the host queen, then uses host workers to raise her brood. The colony structure depends entirely on maintaining live host workers.
  • Colony: Monogyne
  • Queen: Socially parasitic, Temporary parasitic
  • Special: Slave-making
• Size & Growth:
  • Queen: Estimated 7-9mm based on genus patterns
  • Worker: 4.8-6.6mm ^[1]
  • Colony: Unknown, likely under 500 workers based on related species
  • Growth: Slow to moderate, depends on host colony health
  • Development: Unknown, development occurs within host colony (Development timing is unconfirmed as it occurs within the host colony. Expect similar timeline to related Polyergus species (several months to a year for significant growth).)
• Antkeeping:
  • Temperature: Keep at room temperature (20-24°C). This species comes from temperate regions with distinct seasons, so a mild temperature gradient is appropriate. Avoid overheating.
  • Humidity: Moderate to high, they inhabit moist forest habitats. Keep the nest substrate damp but not waterlogged. The host Formica species prefer moist conditions.
  • Diapause: Yes, likely requires a winter rest period (diapause) of 2-3 months at 5-10°C, consistent with their northern temperate distribution.
  • Nesting: This species cannot be kept in isolation. You must maintain BOTH the Polyergus colony AND a healthy host Formica colony. Use standard test tubes or acrylic nests for the host colony. The Polyergus queen will integrate into the host nest. Naturalistic setups with rotting wood work well as this is their natural nesting substrate ^[2].
• Behavior: Polyergus bicolor is an aggressive slave-maker. Workers conduct raids on other Formica colonies, primarily targeting pupae to raise as future host workers. Unlike some aggressive ants, they are not particularly defensive toward keepers, their survival strategy relies on host manipulation rather than direct combat. Escape risk is moderate, workers are medium-sized and can climb smooth surfaces, so standard barriers work well. The biggest behavioral concern is that without a functioning host colony, the Polyergus workers will not survive.
• Common Issues: host colony collapse is fatal, without live host workers, Polyergus bicolor cannot survive as they cannot care for themselves, maintaining two colonies doubles the complexity and cost of care, host colonies may be aggressive and difficult to contain, queen introduction can fail, the host colony may reject or kill the invading queen, without regular raids to replenish host workers, the host portion of the colony will age and die out

Understanding Dulotic Ants

Polyergus bicolor is a dulotic ant, meaning it is a 'slave-maker.' This is one of the most complex ant lifestyles to keep in captivity. Unlike typical ants where the queen raises her own workers, dulotic queens must invade an established colony of their host species, kill or replace the host queen, and trick the host workers into raising Polyergus brood instead of their own ^[2]. The host workers continue all normal colony functions, foraging, nursing brood, maintaining the nest, while the Polyergus workers primarily focus on raiding other colonies to steal more host pupae. This means you cannot keep Polyergus bicolor alone. You must maintain a healthy colony of Formica subaenescens (or occasionally Formica neorufibarbis) as the host ^[1]. Without the host workers, the Polyergus portion of the colony will die.

Housing Requirements

You need two separate setups: one for the host Formica colony and one where the Polyergus queen and her workers will integrate. The host colony can be kept in standard test tubes, acrylic nests, or naturalistic setups with rotting wood (their natural substrate). Formica ants prefer moist conditions, so keep the substrate damp. The Polyergus portion will essentially live within the host nest once the invasion is successful. For the initial introduction, place the Polyergus queen near the host colony entrance, she will release pheromones that trick the host workers into accepting her. This process can take hours to days and may fail. Monitor closely and be prepared to separate if the host workers attack aggressively. ^[3]

Feeding the Colony

The host Formica workers will forage for food and feed the entire colony, including the Polyergus. You should feed the host colony a varied diet: sugar water or honey for energy, and protein sources like mealworms, crickets, or other insects. Formica ants are generalist feeders and typically accept most ant foods. The Polyergus workers will also accept some food directly but rely heavily on the host workers for nutrition. Keep a constant sugar source available and offer protein 2-3 times per week. ^[3]

Seasonal Care and Overwintering

Like other ants from their northern range, Polyergus bicolor likely requires a winter diapause period. During autumn, reduce temperatures gradually to around 5-10°C and keep them there for 2-3 months. This mimics their natural seasonal cycle and is important for colony health. Both the Polyergus and host portions of the colony will slow down during this period. Do not feed heavily during diapause and keep substrate slightly damp but not moist. Return to room temperatures gradually in spring when the colony becomes active again. ^[3]

The Raid: How They Acquire Slaves

One of the most fascinating behaviors of Polyergus bicolor is their raiding behavior. When a colony needs more host workers, Polyergus scouts locate nearby Formica nests and recruit raid parties. During a raid, Polyergus workers rush into the host nest and grab as many pupae as they can carry, then retreat quickly. The stolen pupae are raised by the host workers already in the colony, these emerging workers then become part of the workforce that supports the Polyergus. In captivity, you may observe this behavior if you provide access to a secondary Formica colony, though this is not recommended as it can destabilize your primary host colony. ^[2][1]

Frequently Asked Questions

References