The wall ant
Lasius emarginatus is the Mediterranean, urban cousin of Lasius niger. More heat-loving, it readily settles in wall cracks, under paving, in old masonry. Recognisable by its reddish-brown thorax contrasting with its darker head and gaster.
It’s an active and opportunistic species. In summer, its foraging trails are among the most visible in Mediterranean cities, running across walls, façades and balconies in search of aphid honeydew.
Hardy, undemanding, fast-growing and forgiving of mistakes: L. emarginatus is a perfect first species for a beginner. Very observable surface activity, nuptial flights easy to catch in July-August.
Summer nuptial flights
Flights take place in July-August, often on a warm late afternoon. The queens are frequently found on sunny walls, sometimes on balconies. Founding is claustral: the queen doesn’t go out before the first workers emerge (8-10 weeks at 22-24°C).
The colony reaches 1,000 workers in 2-3 years with good keeping. In the early years, watch the worker castes gradually appear: their size increases as the colony matures.
From a few hundred workers on, L. emarginatus becomes very active and finds every flaw. Paraffin oil or Fluon are essential on the outworld. Also plug the tube-plug joints with tightly packed cotton.
Keeping
Warm temperate, 22-28°C, humidity 50-60% (fairly tolerant). Mandatory winter hibernation (4 months at 8-12°C). Feeding: honeydew or sugar water + occasional insects (fruit flies, small crickets). No active heating needed in a temperate indoor setting.
Frequently asked questions
- How big is Lasius emarginatus?
- Queen: 8-10 — Workers: 3-4.5.
- How long does a Lasius emarginatus queen live?
- A Lasius emarginatus queen lives approximately 15-20.
- How does Lasius emarginatus found a colony?
- Foundation type: Claustral — Polygynous: No.
- What does Lasius emarginatus eat?
- Diet: Aphid honeydew, insects, sugar.
- Does Lasius emarginatus need a diapause (hibernation)?
- Diapause: Yes (Nov-Feb).
- What temperature and humidity does Lasius emarginatus require?
- Temperature: 22-28 — Humidity: 50-60.
- How large does a Lasius emarginatus colony grow?
- Colony size: 5,000-10,000.
- Is Lasius emarginatus suitable for beginners?
- Difficulty level: 2/5 (easy).
Sources & references
Authoritative references for further reading on Lasius emarginatus:
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