Lasius interjectus
Temperature
20–26 °C
Humidity
55–75%
Colony size
3,000–20,000
Queen size
7–9 mm
Worker size
3.5–5 mm
Hibernation temp
6 °C
Diet
Care Guide
Lasius interjectus is a fascinating social-parasitic ant species that begins its life in a rather unconventional way. Unlike typical ant queens, the Lasius interjectus queen cannot start a colony on her own. She must infiltrate an established colony of a host Lasius species, usually Lasius alienus or Lasius niger, and take over the nest by killing or displacing the host queen. The host workers then accept the parasitic queen as their own, raising her brood alongside their own until the parasitic workers emerge and gradually replace the host population. This unique founding strategy makes keeping this species a true test of skill. Queens measure between 7 and 9 mm, while workers are smaller, ranging from 3.5 to 5 mm. Mature colonies can reach 3,000 to 20,000 workers, forming a robust and active population.
The diet of Lasius interjectus closely mirrors that of their host relatives. They thrive on a mix of sugary foods—such as honeydew produced by aphids and diluted sugar water—and insect protein, including flies, mealworms, and crickets. A balanced diet is crucial for healthy brood development and colony growth, especially during the active season when the ants are foraging and expanding.
Care difficulty
Keeping Lasius interjectus is rated as advanced. The primary challenge lies in the founding phase: acquiring a young, freshly mated queen and providing her with a suitable host colony fragment or allowing her to infiltrate a small, established host nest in a controlled setup. Even experienced keepers sometimes struggle to achieve successful adoption. Once the colony is established, care becomes more manageable, but the parasitic nature means these ants may be more sensitive to disturbances during early growth. A deep understanding of host ant husbandry is highly recommended before attempting to keep this species.
Housing
A formicarium with moderate humidity (55–75%) and stable temperatures between 20–26°C works well for Lasius interjectus. The nest should have chambers that can be kept dark and quiet, as these ants are sensitive to vibrations and light disturbances, especially during the critical founding period. Hibernation is mandatory: from late autumn to early spring, the colony must be cooled gradually to around 6°C and kept at that temperature for several months to simulate natural dormancy. Without proper hibernation, the queen may stop laying eggs and the colony’s long-term health will decline.
First days after purchase
If you acquire a Lasius interjectus colony that is already established, place the formicarium in a calm, dimly lit location with minimal foot traffic. Allow the ants several days to acclimatize without disturbance. Ensure a constant supply of sugar water and small live or frozen insects, and check that humidity levels are adequate. Resist the urge to open the nest or shine lights inside—patience is essential. With careful observation and a gentle approach, this parasitic species will reward you with a unique glimpse into one of nature’s most cunning survival strategies.