The red wood ant
Formica polyctena builds a mound of dead vegetable material which is accumulated into a sort of loose thatch. Some taxonomic relatives of
Formica nest beneath rocks and the two nest types are closely related in a physical sense. Possibly this similarity is more than just coincidental. The hypothesis is suggested that the mound of
Formica polyctena has evolved as a simulation of a rock.
Publication of the 
Meijendel-comité
, Nieuwe Serie, No. 51