Lasius vestitus

Lasius vestitus

Lasius vestitus is a small, exceptionally hairy ant species native to the Pacific Northwest of North America. Workers measure around 3-4mm with a pale to medium brown body covered in abundant long standing hairs, particularly on the abdomen, legs, and antennae, giving them a distinctly fuzzy appearance that sets them apart from related species. Queens are larger at 1.37-1.52mm head width and equally covered in dense silky-yellow hairs, with the gaster having a brush-like appearance. This species belongs to the umbratus group within the flavus clade and is closely related to Lasius umbratus but can be distinguished by its unique body pilosity ^[1].

What makes Lasius vestitus particularly interesting is its remarkable cold tolerance, workers have been observed actively foraging on snow in Oregon's Cascade Mountains, making it one of the most cold-adapted ant species in North America. This exceptional hardiness, combined with its distinctive hairy appearance, makes it a rewarding species for keepers interested in a hardy, temperate ant that can handle cooler conditions than most other ants.

Quick Summary

• Difficulty: Easy
• Origin & Habitat: Pacific Northwest of North America (Oregon, Washington, northern California) extending to western Idaho and British Columbia. Found in damp, shaded forest habitats in the Cascade Mountains ^[1][2].
• Colony Type: Temporary social parasite, queens invade colonies of host Lasius species (typically L. neoniger or related species), kill the host queen, and establish their own colony using the host workers. This is a temporary parasitism during founding only.
  • Colony: Monogyne
  • Queen: Temporary parasitic
• Size & Growth:
  • Queen: 1.37-1.52mm head width
  • Worker: Approximately 3-4mm (PW 0.66-0.73mm)
  • Colony: Likely several hundred workers based on typical Lasius umbratus-group patterns, estimated moderate colony size
  • Growth: Moderate
  • Development: 6-8 weeks at optimal temperature (estimated based on typical Lasius development) (Development timeline is estimated from related Lasius species, direct observations for this specific species are not documented)
• Antkeeping:
  • Temperature: Keep cool, this species tolerates temperatures other ants cannot handle. Aim for 15-22°C, with the cooler end being more natural. They can even be active near freezing temperatures in the wild. Room temperature (18-21°C) is ideal. Avoid overheating.
  • Humidity: Moderate to high, they prefer damp forest floor conditions. Keep the nest substrate consistently moist but not waterlogged. Provide a water source.
  • Diapause: Yes, as a cold-adapted temperate species, they require a winter hibernation period. Reduce temperature to 5-10°C for 3-4 months during winter, typically November-February depending on your location.
  • Nesting: In nature they nest under stones, in rotting wood, and in soil in shaded forest habitats. In captivity, a test tube setup works well for founding colonies. Once established, they do well in Y-tong nests, plaster nests, or naturalistic setups with moist substrate. They do not need large spaces, moderate chambers are fine.
• Behavior: Generally peaceful and non-aggressive. Workers are active foragers and will search for honeydew, small insects, and sugar sources. They are not known for stinging, like most Formicinae, they can spray formic acid as a defense but pose minimal danger to keepers. Escape risk is moderate, they are small but not particularly fast-moving. Standard escape prevention (fluon on test tube rims, secure lids) is sufficient.
• Common Issues: cold stress from overheating, keep them cool, not warm like tropical species, finding a host colony for the parasitic queen, wild-caught foundresses may already be in host colonies, colonies can be slow to establish during the parasitic founding transition, excessive humidity can cause mold problems, balance moisture carefully, small colony size initially means slow growth, patience is required

Housing and Setup

For Lasius vestitus, you can start with a simple test tube setup for the founding queen. Since this is a temporary social parasite, wild-caught queens are often already in host colonies, but if you obtain a lone queen, you'll need to introduce her to a host colony (typically Lasius neoniger or similar small Lasius). For established colonies, a Y-tong nest or plaster formicarium works well, these provide good humidity control and allow you to observe the colony easily. naturalistic setups with soil and stones also work, mimicking their natural forest floor habitat. Keep the nest area dark or covered to reduce stress, as these ants prefer dim conditions. ^[1]

Feeding and Diet

Lasius vestitus workers are opportunistic foragers that accept a variety of foods. Offer sugar water, honey, or diluted syrup as a constant carbohydrate source. For protein, provide small insects like fruit flies, small crickets, or mealworm pieces. They will also collect honeydew from aphids if available. Feed protein sources 2-3 times per week, and keep sugar water available at all times. Remove uneaten food after 24-48 hours to prevent mold. In myrmecaria setups, they may tend aphids on plant roots, which can be an interesting addition.

Temperature and Seasonal Care

This species is exceptionally cold-tolerant, so keep them on the cool side, 15-22°C is ideal, with 18-21°C being optimal for most keepers. They can tolerate temperatures near freezing and have been observed foraging on snow in the wild. This means you should avoid heating the nest, room temperature is often perfect. During winter, provide a true hibernation period: reduce temperature to 5-10°C for 3-4 months (typically November through February). Place the colony in a cool basement, garage, or refrigerator (not freezer) during this time. Do not feed during hibernation. This winter rest is essential for colony health and reproduction. ^[1]

Colony Establishment and Growth

Lasius vestitus uses a temporary parasitic founding strategy, the queen invades a colony of host Lasius species (typically L. neoniger or related species), kills the host queen, and uses the host workers to raise her brood until her own workers emerge. This means wild-caught colonies often come with host workers already present. If establishing from a lone queen, you will need to carefully introduce her to a small host colony, this can be tricky and success is not guaranteed. Once established, colonies grow moderately, typically reaching several hundred workers over 2-3 years. Growth is faster during the active season and slows during hibernation.

Behavior and Observation

These ants are relatively calm and not aggressive toward keepers. Workers are active foragers that will readily explore and collect food. They are primarily nocturnal or crepuscular in activity, so they may be most active in the evening or with reduced lighting. The most striking feature is their dense body pilosity, the long standing hairs give workers and queens a fuzzy, almost brush-like appearance that is quite distinctive. They communicate using chemical trails and will recruit nestmates to food discoveries. While they can spray formic acid as a defense, they pose minimal sting risk to humans.

Frequently Asked Questions

References