Prenolepis tosa

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to Japan, specifically Kochi Prefecture (Tosashimizu, Cape Ashizuri) in the Palaearctic region. This species is strictly arboreal, nesting on the trunks of broad-leaved trees like Camellia japonica at considerable heights above ground ^[1].
• Colony Type: Colony structure is unconfirmed. The type colony was found with multiple workers, and lab rearing produced both males and females from collected larvae, suggesting multi-worker colonies exist. Further research is needed to determine whether they are monogyne (single queen) or polygyne (multiple queens).
• Size & Growth:
  • Queen: ~3.9 mm ^[1]
  • Worker: ~2.2-2.3 mm ^[1]
  • Colony: At least 20 workers in type colony ^[1]
  • Growth: Unknown, no published data on colony growth rate
  • Development: Unknown, no direct observations of egg-to-worker development have been published (Lab rearing produced alates from collected larvae, but founding behavior and development timeline remain unstudied)
• Antkeeping:
  • Temperature: Room temperature (18-25°C) is likely suitable. No specific thermal studies exist, but lab rearing succeeded at room temperature ^[1]. Start around 20-24°C and monitor colony activity.
  • Humidity: Moderate to high humidity likely preferred, reflecting their arboreal forest habitat. Avoid overly dry conditions. Provide a moist area in the nest without waterlogging.
  • Diapause: Unknown, no studies on overwintering requirements. Japan has cold winters, so a cool period (15-18°C) for a few months may be beneficial, but this is unconfirmed. Observe colony behavior.
  • Nesting: This is an arboreal species, they naturally nest on tree trunks. In captivity, provide vertical climbing structures (branches, cork, or vertical formicarium chambers). They will not accept horizontal soil nests. A naturalistic setup with vertical surfaces or a custom arboreal formicarium works best.
• Behavior: Workers are active on tree surfaces and likely forage on bark. No ground activity has been observed ^[1]. They are small (2.2 mm workers) so escape prevention must be thorough, fine mesh or fluon barriers on all openings. Temperament is not well documented but Prenolepis species are generally non-aggressive. The three ocelli (small eyes on top of the head) suggest some light sensitivity, though their primary navigation is likely chemical.
• Common Issues: Limited husbandry information, this species was only described in 2019 and captive care methods are unproven., Strict arboreal requirements, horizontal nests and soil setups will not work, vertical surfaces are essential., Small size (2.2 mm workers) increases escape risk, ensure all openings are sealed with fine mesh or fluon.

Arboreal Nesting Requirements

Prenolepis tosa is unique among Prenolepis species as the first documented arboreal ant in this genus. In the wild, colonies nest on tree trunks at heights of 80-120 cm above ground, with multiple nest entrances ^[1]. Workers forage exclusively on bark surfaces and have never been observed on the ground ^[1]. This means your captive setup must provide vertical space for climbing and nesting. Horizontal soil nests will not be accepted. Instead, use naturalistic setups with vertical branches, cork bark, or custom vertical formicaria. The ants need surfaces they can walk up and down, not flat horizontal chambers. Think of it as recreating a tree trunk environment rather than a typical ant nest.

Feeding and Diet

Diet preferences have not been specifically studied for Prenolepis tosa, but related Prenolepis species are omnivorous, feeding on honeydew, small insects, and nectar. Based on their small size (2.2 mm workers), offer small prey items like fruit flies, pinhead crickets, and springtails. Sugar sources like honey water or sugar water should be available. Since they are arboreal foragers on tree bark, they likely encounter and collect honeydew from aphids and scale insects in nature. Feed small amounts of protein (insects) 2-3 times per week and keep sugar water constantly available. Remove uneaten prey within 24-48 hours to prevent mold.

Temperature and Seasonal Care

No specific temperature requirements have been documented for this species. Based on its origin in Kochi Prefecture, Japan (a temperate region), room temperature between 18-24°C should be suitable. The species has been successfully reared in laboratory conditions at room temperature ^[1], suggesting they are adaptable. Since they are arboreal and found in forest habitats, avoid extreme temperatures and sudden fluctuations. A heating cable on one side of the nest can provide a gentle gradient if your room runs cool. During winter, a cool period matching indoor room temperatures (15-18°C) may simulate natural seasonal changes, though their exact overwintering requirements remain unknown.

Colony Rearing Observations

The only published captive observations come from the original researchers who collected 20 workers and 15 larvae from the type colony and reared them in a polystyrene observation nest ^[1]. They successfully produced alates (reproductive ants): males emerged on 22 June and 2 July 2014,while females emerged on 16 July and 19 July 2014 ^[1]. This suggests the reproductive season occurs in mid-summer. The colony was maintained in a simple room-temperature setup, showing that basic care is straightforward. However, this limited data point represents the entirety of what we know about captive husbandry for this species.

Escape Prevention and Handling

At 2.2 mm, workers are small ^[1]. Standard escape prevention measures (fluon barriers, tight-fitting lids) should be adequate, but due to their arboreal nature, they are active climbers. Use barrier tape on the edges of any formicarium and ensure all connections are secure. Fine mesh may be needed to cover ventilation holes. When handling, remember these ants are delicate due to their small size. Avoid disturbing the nest excessively, especially during founding or when brood is present.

Frequently Asked Questions

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References