Myrmica jessensis

Quick Summary

• Difficulty: Easy
• Origin & Habitat: Japan, Korea, and Russian Far East. In Japan it's common in open grasslands, bare lands, dry riverbeds, and mown roadside verges, nesting under stones in soil ^[2][3][5]. Also found in conifer-broadleaf and semi-evergreen broadleaf forests up to 2554 m ^[4].
• Colony Type: Unconfirmed – colony structure not specifically studied. Based on typical Myrmica genus patterns, likely single-queen colonies.
• Size & Growth:
  • Queen: Estimated 5–7 mm based on typical Myrmica queen size (no direct data)
  • Worker: 4.0–5.0 mm ^[1]
  • Colony: Estimated up to several thousand workers based on typical Myrmica colony sizes (no direct data)
  • Growth: Moderate
  • Development: Estimated 6–10 weeks based on typical Myrmica development (inferred from genus patterns) (Actual timeline may vary – development depends on temperature and colony conditions.)
• Antkeeping:
  • Temperature: Keep at 20–24°C during the active season. Based on its temperate range and high-altitude habitats, it tolerates cooler conditions. Provide a gradient so workers can choose. Avoid prolonged temperatures above 28°C.
  • Humidity: Moderate humidity. In the wild it nests in well-drained soil under stones. Keep the nest substrate moist but not waterlogged, with some drier areas available ^[4].
  • Diapause: Yes – as a temperate species from Japan, Korea, and Russia, colonies need a winter dormancy. Gradually lower temperature to 5–10°C and maintain for 3–4 months.
  • Nesting: Y-tong (AAC) or plaster nests work well. Provide a soil-like substrate with flat stones to mimic natural nesting sites. Include some chambers that stay relatively dry along with moderately moist areas.
• Behavior: Workers are active foragers that hunt small invertebrates and attend aphid colonies for honeydew ^[6]. They aren't especially aggressive toward humans but will defend the nest. They have a functional stinger, but at 4–5 mm size it rarely penetrates human skin. Standard escape prevention is sufficient – they aren't extreme climbers.
• Common Issues: colonies may fail if not given proper hibernation – temperate Myrmica need winter rest., overheating is a risk – avoid temperatures above 28°C., colonies grow slowly during the first year – patience is required., wild-caught colonies may carry parasites that need treatment., dry conditions cause colony decline – monitor substrate moisture.

Nest Preferences

In the wild, Myrmica jessensis nests in soil, often under stones ^[2][3][4]. It favors open habitats like grasslands, dry riverbeds, and roadside verges where the ground is well-drained. For captive care, use a Y-tong (AAC) or plaster formicarium. Add a layer of soil or substrate to allow natural tunneling. A naturalistic setup with flat stones placed on soil mimics their preferred nesting sites. The nest should have chambers that stay relatively dry alongside moderately moist areas.

Feeding and Diet

Myrmica jessensis is predatory and also tends aphids for honeydew ^[6]. In Chinese larch forests it actively hunts larvae of Cephalcia lariciphila, a forest pest ^[1]. For captive colonies, offer protein sources like small insects (fruit flies, small mealworms, crickets) 2–3 times per week. Provide sugar water or honey continuously. They accept both protein and sugars.

Temperature and Seasonal Care

This species comes from temperate regions and experiences cold winters. It requires a diapause (hibernation) period. Keep the colony at 20–24°C during the active season. In autumn, gradually reduce temperature to 5–10°C and maintain this for 3–4 months of winter dormancy. This rest is essential for colony health and reproduction. Avoid temperatures above 28°C – overheating can be fatal. A heating cable on one side of the nest creates a useful temperature gradient. ^[2][3][5]

Behavior and Temperament

Workers are active foragers that search for prey and honeydew. They aren't particularly aggressive toward humans but will defend the nest against intruders. Like other Myrmica species, they have a stinger, but at 4–5 mm it rarely penetrates human skin. They aren't known as extreme escape artists, but standard escape prevention (fluon barriers, tight lids) should still be used. Colonies are moderately fast-growing once established, with workers living several months. ^[1]

Growth and Development

Nuptial flights happen in September, when winged queens and males leave the nest to mate ^[5][3][2]. After mating, queens dig chambers in soil to start new colonies. The first workers (nanitics) are smaller than mature workers and appear after several months. Based on typical Myrmica development, expect 6–10 weeks from egg to first worker under optimal conditions. Growth is moderate – colonies may take a year or more to reach 100 workers. Patience is key during the founding stage.

Frequently Asked Questions

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References