Lasius neglectus may invade the interior of houses and occupy electrical conduits, causing short-circuits or damage to electro-mechanical devices. Outdoors, it nests at the base of plants and attends aphids on trees, usually producing negative effects. As a result of the ants protecting aphids and "milking" them for their honeydew it causes honeydew to be produced in large quantities, in turn causing sooty mould to grow on leaves.
Not all populations seem to be invasive, in Spain only three out of eleven populations have been denounced as damaging or invasive. This is probably due to climatic constraints, especially dryness during the Mediterranean summer.
Location Specific Impacts:
Competition: Lasius neglectus displaces the native ant Lasius grandis. This invasive ant is able to achieve higher honeydew collection through its greater abundance and "greater level of attention towards promoting an increase of honeydew production" (Paris & Espadaler, 2009).