Lasius hayashi

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to Japan, Korean Peninsula, Russian Far East, and China. Found in shady deciduous woodland with large trees, nesting in tree trunks and root systems at elevations up to 600 m in Hokkaido and 1600 m in Shikoku ^[1][2].
• Colony Type: Unconfirmed – colony structure not explicitly described in the literature. Type series included multiple queens from one nest, but whether they coexist is unknown.
• Size & Growth:
  • Queen: 7-8 mm ^[2]
  • Worker: 2-4 mm ^[3][2]
  • Colony: Unknown – likely several thousand workers at maturity, estimated from related Lasius s.str. species.
  • Growth: Moderate
  • Development: 6-10 weeks (estimated based on Lasius s.str. patterns) (Direct development data unavailable, inferred from related species. Nuptial flights occur July-August, suggesting a spring-summer founding cycle.)
• Antkeeping:
  • Temperature: Keep at 20-24°C. This species tolerates cooler temperatures than many ants – in their native range they remain active until mid-November and nuptial flights occur at 22-24°C ^[1]. Room temperature is usually suitable.
  • Humidity: Moderate humidity. Nest the colony in a Y-tong (AAC) or plaster nest with a water tube as the main moisture source. Avoid waterlogging – this species nests in tree trunks and root systems in humid but not soaked conditions.
  • Diapause: Yes – required for colony health. Based on their northern distribution and activity until mid-November, they need a winter rest period of 3-4 months at 5-10°C ^[1][2].
  • Nesting: Prefers arboreal or root-system nesting. In captivity, Y-tong (AAC) or plaster nests work well. They do best with some vertical space and prefer darker areas – this is a forest-dwelling species that avoids bright light ^[1][2].
• Behavior: Generally peaceful but defensive when threatened. Workers take on a defensive posture similar to Formica truncorum when attacked, though far less exaggerated ^[2]. They are active foragers that move rapidly ^[4] and show a strong dependence on tending aphids (Homoptera) – more so than other Lasius species in their area ^[1][2]. Escape risk is moderate – workers are 2-4 mm, so secure barriers are needed.
• Common Issues: colonies may fail if kept too warm year-round – they need a winter cooling period., wild-caught colonies from tree hollows can be difficult to establish in captivity., foraging trail covers may be misinterpreted as mold by new keepers., they strongly prefer arboreal aphid honeydew – sugar water alone may not sustain colonies long-term., slow founding phase (typical of Lasius) can frustrate those new to ant keeping.

Housing and Nest Setup

Lasius hayashi naturally nests in hollow trunks and root systems of large deciduous trees ^[1][2]. In captivity, they do well in Y-tong (AAC) or plaster nests that provide dark, humid chambers. Avoid bright lighting near the nest – this is a shade-loving species. A test tube setup works for founding colonies, but established colonies benefit from more space. The outworld should include climbing structures since they are arboreal foragers. Keep the nest moderately humid with a water tube, but avoid excessive moisture that could cause mold in the foraging area.

Feeding and Diet

Like other Lasius species, L. hayashi is omnivorous but shows a strong preference for honeydew from aphids ^[1][2]. In captivity, offer sugar water or honey water as a constant energy source. They also accept protein from small insects. What makes this species unique is their heavy dependence on arboreal Hemiptera – they maintain and protect aphid colonies more intensively than related species ^[1][2]. If possible, provide access to small aphid colonies or substitute with regular sugar offerings. Protein should be offered 1-2 times weekly. Their foraging trails are covered with plant material in the wild, which may relate to their aphid-tending behavior ^[1][2]. They have been recorded associating with the butterfly Niphanda fusca (obligate, parasitic) ^[5] and the rove beetle Diartiger fossulatus tadauchii ^[6].

Temperature and Seasonal Care

Lasius hayashi tolerates cooler temperatures than many ants – they remain active in Sapporo until mid-November, later than sympatric L. niger and L. sakagamii ^[1][2]. Keep the nest at 20-24°C as a baseline, room temperature is often suitable given their cool-temperate origin. They require a winter dormancy period of 3-4 months at 5-10°C to maintain healthy colony cycles. This can be provided by moving the colony to an unheated garage or refrigerator during winter. The nuptial flight period in July-August occurs at relatively cool evening temperatures (22-24°C) and low light intensities (0-10 lux) ^[1][2], confirming they prefer not overly warm conditions.

Behavior and Colony Dynamics

This species exhibits several distinctive behaviors. Workers cover their foraging paths with macerated plant material and humus – this is more pronounced than in related species and serves to protect their trails while tending aphids ^[1][2]. When threatened, they display a defensive posture similar to but less exaggerated than Formica truncorum ^[2]. They are rapid movers compared to similar-sized ants ^[4]. Colonies grow moderately – founding can be slow as with most Lasius, but established colonies develop steadily. Queens are 7-8 mm and workers 2-4 mm ^[2]. Alates (sexuals) are produced in summer, with nuptial flights from early July to late August, starting in late evening ^[1][2]. Workers have no spermatheca and cannot become gamergates ^[7].

Founding and Early Colony Development

Founding behavior is unconfirmed for this species, but based on typical Lasius s.str. patterns, new colonies are likely founded claustrally – the queen seals herself in a chamber and raises the first workers on stored body fat without foraging. This process typically takes 6-10 weeks at optimal temperature. Founding colonies should be kept in darkness with minimal disturbance. The first workers (nanitics) will be smaller than mature workers. Once workers emerge, the colony can be fed small amounts of sugar water and tiny protein items. Growth is moderate – patience is required during the founding phase as with all Lasius species. ^[2]

Frequently Asked Questions

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References