Lasius

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Lasius is a genus of formicine ants.<ref>Template:Cite web</ref> The type species for this genus is the black garden ant, Lasius niger. Other major members, which live in drier heathland, are the cornfield ant, L. neoniger, and L. alienus. Other species include the temporary social parasites of the L. mixtus group and the hyper-social parasite Lasius fuliginosus. Lasius flavus is also a commonly seen species, building grassy hillocks in undisturbed pasture. In the Alps, these mounds – always aligned east to catch the first rays of the rising sun – have been traditionally used by goatherds as natural compasses.Template:Citation needed Species in the subgenus Acanthomyops, in particular L. interjectus and L. claviger, are commonly known as citronella ants due to their citronella-like smell.

Social parasitism

Several species in this genus are noted to be social parasites.<ref name=":0">Template:Cite web</ref><ref name=":1">Template:Cite web</ref><ref>Template:Cite web</ref><ref name=":2">Template:Cite web</ref> Some species such as Lasius latipes and Lasius murphyi are noted to have their mating flights in mid-late summer and invade other colonies of Lasius, primarily Lasius neoniger.<ref name=":0" /><ref name=":1" /><ref name=":2" /> Other species, such as Lasius claviger, are known to overwinter and invade colonies in the spring.<ref>Template:Cite web</ref><ref name=":2" />

Moisture ants

Many Lasius species, known collectively as "moisture ants" in the United States, make their nests in and around moist rotting wood as well as under rocks.<ref name="Klotz1">Template:Cite book</ref><ref name="Klotz2">Template:Cite book</ref> They can infest buildings, particularly foundation forms in contact with soil, becoming a minor nuisance.<ref name="WSU">Template:Cite web</ref><ref name="Klotz1" /> They are not considered a structural threat because they only make their galleries in wood that is already decayed.<ref name="WSU" /> Some species build "cartonlike" nests in moist locations made of decayed wood fragments cemented together with honeydew and the ant's mandibular gland secretions.<ref name="Klotz2" /> Workers are monomorphic, 2 to 3 mm long, yellow to dark brown.<ref name="Klotz1" /> They are secretive, and forage mostly at night for honeydew and other sweet substances, and may also prey on small insects.<ref name="Klotz1" /> Winged reproductive males and females swarm in late summer and fall, which is when building infestations may be noticed.<ref name="Klotz1" /> They are distinguished from carpenter ants (Camponotus), another structure-infesting species, by being much smaller, and having a notch in the dorsal thorax (top of the center body division), where carpenter ants have a rounded thorax.<ref name="WSU" /><ref name="Klotz1" /> Widespread moisture ant species include L. alienus and L. neoniger, as well as some Acanthomyops species.<ref name="Klotz2" />