Myrmecologische Nachrichten 2: 19-34
Myrmecologische Nachrichten 2: 19-34; printable
Abstract: This is the fIrst observation that a member of the Formica exsecta-group ( subgenus = Coptojormica) has carried out a raid against a potential host species. Workers of Formica exsecta invaded a nest of Formica lemani (Mount Göller, Lower Austria), cut off the heads of their opponents and carried the F ormica lemani-bodies back to their nest. The decapitated Formica lemani-bodies show characteristic injuries which make it possible to reconstruct the subterranean encounter. The Formica exsecta-group is distinctive by a deep concave occipital margin and prebasal denticels on the mandibel. Furthermore they have a strong biting force which can be seen in the crunched plant material used for nest building and in decapitation of their enemies. The strong biting force, the occipital margin and the prebasal denticles are probably the result of a change in the length of the .mandibular lever arms. Formica exsecta is a strictly territorial species and displaces other little predators and territorial ants. On the contrary, it is astonishing peacefully against its hostspecies Formica fusca and Formica lemani. These common attributes of Formica exsecta are .contradictory to the observation from Mt. Göller. The host species are not serious contenders for food but they could be used by Formica exsecta by facultative social parasitism or simply as source of food. In the latter case it is possible to store energy for times of lack in food ressourees.