The ant responsible for this new infestation, Lasius brunneus (Latreille), has bicoloured workers in which the blackish gaster contrasts with the brown colour of the head and the thorax. Length of workers is variable, from 2 mm to 4 mm.


lateral view

head frontal view



queen taken care of by her workers. This is the first queen found in Spain.

The workers of Lasius brunneus are readily differentiated from those of other ants that nest in cork. Crematogaster scutellaris, that also causes damage to young cork-oaks, is bigger (3.5 - 5 mm) and has a red head. When disturbed, workers raise the abdomen. Camponotus fallax (Nylander) is even larger and is completely dark in colour. Another ant species that can also be present in the cork–oak, and with which it could easily be confused, is Lasius lasioides, smaller in size and usually of more uniform body colour. In Catalonia these two species have a different ecology when nesting in cork-oak: Lasius brunneus is found at higher altitudes and in zones with lower temperatures and greater precipitation.


Page authors: Xavier Espadaler  ( and Víctor Bernal (