Polyrhachis illaudata

Polyrhachis illaudata

Polyrhachis illaudata is a medium-sized ant native to South and Southeast Asia, ranging from Sri Lanka across India, through Malaysia and Indonesia to the Philippines and southern China. Workers measure 8.7-10.5mm and are jet black with a striking covering of dense golden decumbent hairs that gives them a golden sheen under light. They belong to the subgenus Myrma, which is known for producing pupae enclosed in cocoons, a trait shared with weaver ants but not all Polyrhachis. Their most notable behavior is flexible nesting: they can nest in soil or under tree bark, and colonies are polydomous, meaning they maintain multiple nest sites across their territory ^[1][2][3].

What makes P. illaudata particularly interesting is their variable nesting habits and social structure. Unlike many ants that pick one nesting spot, these ants maintain multiple connected nests (polydomous colonies) and can switch between ground-nesting and arboreal nesting depending on conditions. They forage during the day, forming recruitment trails to food sources, and are known to tend homopterans and feed from extrafloral nectaries. Colonies are single-queen (monogyne) but spread across multiple nest sites ^[2][3].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to South and Southeast Asia including Sri Lanka, India, Bangladesh, Nepal, Thailand, Malaysia, Indonesia (Sumatra, Java, Borneo), the Philippines, and southern China. Found in wet tropical and subtropical forests, typically in primary forest habitats at elevations from 500-1200m. A habitat specialist restricted to primary forest, not found in secondary forest or plantation areas ^[4][5][6].
• Colony Type: Monogyne (single-queen colonies) with polydomous nesting, colonies maintain multiple connected nest sites rather than a single nest. Queens are not multiple within a single nest, but the colony spreads across several locations ^[2].
  • Colony: Monogyne
  • Founding: Claustral
• Size & Growth:
  • Queen: Estimated 12-14mm based on genus patterns, queen size not directly documented in available research
  • Worker: 8.7-10.5mm ^[7][1]
  • Colony: Colony size not directly documented, polydomous colonies likely reach several hundred workers based on related species
  • Growth: Moderate, based on typical Polyrhachis development patterns
  • Development: Estimated 6-8 weeks based on related Polyrhachis species and tropical ant development patterns (Development time is inferred from genus-level data, direct measurements for this species are not available. Cocoon stage is present as confirmed by field observations ^[2].)
• Antkeeping:
  • Temperature: Keep at 24-28°C as a starting point. This is a tropical species from warm, humid forests, they tolerate temperatures into the low 30s but prefer stable warmth. Room temperature (22-26°C) is typically suitable. A gentle heat gradient allows them to regulate their temperature ^[8].
  • Humidity: High humidity is essential, think damp tropical forest floor. Keep nest substrate consistently moist but not waterlogged. Provide a water tube and mist occasionally, but avoid constant dampness that promotes mold. A humidity range of 70-85% is ideal ^[8].
  • Diapause: No, this is a tropical species that does not undergo true hibernation. However, activity may slow during cooler winter months in temperate climates. Keep temperatures stable year-round ^[8].
  • Nesting: Flexible nesting preferences, in nature they nest in soil or under tree bark. For captivity, a test tube setup works for founding colonies. As colonies grow, they may benefit from a formicarium with both ground-level chambers and vertical/arboreal space. They do not use plant material to construct nests like weaver ants, but they do build saucer-shaped soil chambers ^[2][8].
• Behavior: Workers are active during the day (diurnal) and forage on the ground, in shrubs, and in trees. They use group recruitment to food sources, forming short-term trails. They are not particularly aggressive but will defend their nest. Workers are medium-sized (8.7-10.5mm), escape prevention should be standard but they are not extreme escape artists like tiny species. They tend homopterans for honeydew and feed from extrafloral nectaries, making them somewhat arboreal in their foraging ^[3][9].
• Common Issues: colonies may fail if humidity drops too low, these are tropical ants adapted to consistently damp conditions, polydomous nesting means they may try to establish secondary nests outside the main formicarium if given the opportunity, wild-caught colonies may carry parasites including the zombie ant fungus (Ophiocordyceps) which has been documented infecting this species ^[11][12], slow growth compared to faster-developing tropical ants may frustrate beginners, they may not accept test tube setups long-term if they prefer the flexibility of multiple nest sites

Housing and Nest Setup

For founding colonies, a standard test tube setup works well, queen seals herself in a chamber with some damp cotton. Once workers arrive (typically 6-8 weeks), you can keep them in the test tube for several months. As the colony grows to 20+ workers, consider moving to a formicarium. Because they are polydomous in nature, providing some vertical space and multiple connected chambers can help them feel more at home. A Y-tong (acrylic) nest or plaster nest with a water chamber works well, just ensure the nest material stays damp. They don't need the elaborate plant-material weaving that true weaver ants (Oecophylla) do, but they do appreciate having their brood chambers kept humid ^[2][8].

Feeding and Diet

Polyrhachis illaudata is omnivorous with a preference for carbohydrate sources. In the wild, they feed extensively on honeydew from tended homopterans and nectar from extrafloral nectaries. They also scavenge dead insects and other protein sources. In captivity, offer sugar water or honey water constantly, they will readily drink it. For protein, provide small insects like fruit flies, small mealworms, or cricket pieces. Feed protein 2-3 times per week, and keep sugar water available at all times. They are daytime foragers, so offer food during daylight hours for best acceptance ^[3][10].

Temperature and Seasonal Care

These are tropical ants requiring warm, stable temperatures. Keep the nest area at 24-28°C. They can tolerate brief periods higher or lower, but prolonged cold will slow or stop brood development. Unlike temperate species, they do not need a winter diapause, maintain consistent temperatures year-round. If your room temperature drops below 22°C in winter, use a heating cable on one side of the nest to maintain warmth. Avoid placing the heat source directly on the nest as it can dry out the substrate too quickly, instead, create a gentle temperature gradient so workers can move to warmer or cooler areas as needed ^[8].

Colony Structure and Polydomous Behavior

One of the most interesting aspects of P. illaudata is their polydomous colony structure, they maintain multiple nest sites that are connected by trails. In the wild, a single colony may have nests in both soil and under tree bark, using different locations for different purposes (brood chambers vs. food storage, for example). In captivity, this means they may try to establish secondary nests if given access to additional space. This is not a problem, it's natural behavior. You might notice workers moving brood between chambers or establishing new nest sites within their enclosure. The colony has a single queen, but she may be in one nest while workers maintain others, this is normal and not a sign of queen loss ^[2][3].

Health Concerns

One significant concern with this species is their susceptibility to the zombie ant fungus Ophiocordyceps unilateralis, which has been documented infecting P. illaudata in the wild. The fungus emerges from the ant's neck and produces spores that infect other ants. While this is primarily a concern for wild-caught colonies, it's worth being aware of. Signs include unusual behavior, ants dying while gripping leaves or surfaces, and fungal growth emerging from the ant's body. Maintain good hygiene, avoid introducing wild ants or soil from known infected areas, and quarantine new colonies before combining them with existing ones ^[11][12].

Nuptial Flights and Reproduction

Nuptial flights have been observed occurring just after heavy rain, around midnight (0030 hours) in July. This matches the typical pattern for many tropical ants, monsoonal rains trigger reproductive swarms. Alates (reproductives) were observed near lights approximately 100 meters from the nest entrance. If you are keeping this species long-term and want to observe nuptial flights, maintain warm temperatures year-round and ensure the colony is well-established (typically 100+ workers). After mating, newly mated queens will seek out suitable founding sites, in captivity, provide them with test tube setups for claustral founding ^[8].

Frequently Asked Questions

References