Lasius casevitzi

Lasius casevitzi

Lasius casevitzi is a small, dark brown ant belonging to the Lasius paralienus species complex within the Lasius niger clade ^[1]. Workers measure approximately 0.85mm in body length and feature notably long maxillary palps and a dense whitish pubescence covering their entire body ^[1][2]. The species was only described in 2016 and was originally thought to be endemic to Corsica, but has since been discovered in Trieste (northeastern Italy), Sicily, and the Aeolian Islands ^[2][3][4].

This species prefers semi-arboreal habitats and dry open forest, nesting in soil under trees or beneath stones ^[1][2]. It avoids coastal environments and high elevations above 1100m, with most nests found between 300-800m altitude ^[1]. Workers are known to behave aggressively when their nest is disturbed ^[1]. The species forms a well-supported clade with L. paralienus, from which it was only recently separated based on subtle but consistent morphological differences ^[4].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Mediterranean islands (Corsica, Sicily, Aeolian Islands) and northeastern Italy (Trieste). Prefers semi-arboreal habitats and dry open forest, nesting in soil under trees or under stones ^[1][2]. Found from sea level to 1100m altitude, most commonly between 300-800m.
• Colony Type: Single-queen colonies (monogyne), typical for Lasius s. str. species. Colony structure in this species has not been directly studied but follows the genus pattern.
  • Colony: Monogyne
  • Founding: Claustral
• Size & Growth:
  • Queen: Approximately 1.65mm head width (HW) ^[5]
  • Worker: Approximately 0.85mm (CS 849 ± 41 µm) ^[1][2]
  • Colony: Unknown for this species, likely several hundred workers based on typical Lasius paralienus complex patterns
  • Growth: Moderate, based on related species in the Lasius alienus complex
  • Development: Estimated 6-10 weeks at optimal temperature (based on typical Lasius development patterns) (Direct development data not available for this species. Estimates based on genus-level patterns for small Lasius species.)
• Antkeeping:
  • Temperature: Keep at 20-25°C. As a Mediterranean species from Corsica and Sicily, they prefer warmer conditions than northern Lasius species. A gentle temperature gradient allows workers to self-regulate ^[1][2].
  • Humidity: Moderate humidity, they nest in soil in dry open forest, so avoid overly damp conditions. Keep the nest substrate lightly moist but allow it to partially dry between waterings. This species tolerates drier conditions than many Lasius ^[1][2].
  • Diapause: Yes, as a temperate Mediterranean species, they require a winter rest period. Reduce temperature to 10-15°C for 2-3 months during winter, mimicking natural seasonal cycles ^[1][2].
  • Nesting: Y-tong (AAC) nests or plaster nests work well. They prefer dry to moderately humid conditions. Provide a shallow water reservoir but avoid flooding. Naturalistic setups with stones over soil also suit their natural nesting behavior under stones ^[1].
• Behavior: Workers are small at ~0.85mm and very active. They are known to be aggressive when their nest is disturbed, this defensive behavior carries over to captivity, so handle the nest gently ^[1]. They are foragers and will readily search for food. Escape prevention is important due to their small size, use fine mesh barriers and ensure all connections are sealed. They readily accept sugar water and protein foods.
• Common Issues: small size means escapes are likely without fine mesh barriers, aggressive defensive behavior when nest is disturbed, work gently around colonies, limited distribution in the hobby means established colonies may be difficult to find, winter diapause is required, colonies that aren't cooled properly may decline, dry forest habitat means overwatering can cause mold problems

Nest Preferences and Setup

Lasius casevitzi naturally nests in soil, under trees, or under stones in dry open forest and semi-arboreal habitats ^[1][2]. In captivity, they adapt well to various nest types. Y-tong (AAC) nests or plaster nests work particularly well because they allow you to control humidity levels while providing the dark, enclosed spaces these ants prefer. Avoid overly humid conditions, this species comes from relatively dry Mediterranean habitats. Provide a shallow water reservoir connected to the nest area, but ensure it cannot flood the chambers. A small outworld for foraging completes the setup. Because workers are tiny (~0.85mm), ensure all connections and barriers are tight-fitting with no gaps larger than 1mm.

Feeding and Diet

Like other Lasius species, Lasius casevitzi is omnivorous with a preference for sugar sources and protein. Offer sugar water or honey water regularly as a constant energy source. For protein, provide small insects such as fruit flies, small mealworms, or other tiny arthropods. They will also scavenge on dead insects. In the wild, they likely tend aphids for honeydew, so sugar sources are definitely accepted. Feed protein 2-3 times per week, and keep sugar water available at all times. Remove uneaten prey after 24-48 hours to prevent mold. Given their small size, prey items should be appropriately sized, very small pieces or tiny insects. ^[1]

Temperature and Seasonal Care

As a Mediterranean species from Corsica and Sicily, Lasius casevitzi prefers warmer temperatures than northern European Lasius species. Keep the nest area at 20-25°C, with a gentle gradient if possible so workers can choose their preferred temperature ^[1][2]. Room temperature in most homes (20-22°C) should be suitable. During winter, they require a diapause period, reduce temperatures to 10-15°C for 2-3 months to mimic natural seasonal cycles ^[1][2]. This winter rest is important for colony health and may trigger reproductive behavior in mature colonies. Do not cool them suddenly, allow a gradual temperature reduction over 1-2 weeks in autumn.

Behavior and Handling

Lasius casevitzi workers are known to be aggressive when their nest is disturbed, they will readily defend against threats ^[1]. This defensive behavior carries over to captivity, so work gently around the colony and avoid sudden vibrations or frequent nest inspections. Despite their small size, they are active foragers and will quickly explore the outworld in search of food. They are not escape artists in the traditional sense (they don't climb smooth surfaces exceptionally well), but their tiny size means they can squeeze through very small gaps. Use fine mesh on all ventilation holes and ensure tube connections are secure. When the colony grows, they may become more defensive, this is normal Lasius behavior.

Colony Development

Lasius casevitzi is a recently described species (2016), and detailed captive breeding data is not yet available. Based on typical Lasius patterns, claustral founding queens will seal themselves in a small chamber and raise the first brood using stored fat reserves ^[1]. The first workers (nanitics) will be smaller than mature workers and will emerge after approximately 6-10 weeks at optimal temperature. After that, colony growth is moderate, expect several months to reach 50 workers, and potentially a year or more to reach several hundred. Queen longevity in the wild is several years, so established colonies can grow substantial over time. The species is still rare in the hobby, so acquiring a founding colony may require connecting with specialized breeders.

Frequently Asked Questions

References