Aphaenogaster senilis Mayr (Hymenoptera, Formicidae): A possible parasite in the myrmecochory of Euphorbia characias (Euphorbiaceae)

The response of Aphaenogaster senilis workers to the seeds of the myrmecochorous Euphorbia characias shows a remarkable degree of variation. Two factors influencing this response are: 1) worker age: young workers, still performing nest cleaning activities, may transport the seed and discard it intact far from the nest; older workers may ignore the seed or take it to the nest; 2) seed location in relation to the nest entrance and the external midden: seeds fallen between nest entrance and midden may be carried into the nest or taken outside the midden; seeds found outside of the refuse pile are ignored or transported to the nest. Seeds transported to the nest are deprived of the elaiosome and discarded in the refuse heap or farther away within a short time. Those remaining amid the debris may germinate but do not establish. Since seeds that are discarded far from the midden are attractive nearly only to granivorous ants, Aphaenogaster senilis may act as a parasite of the diffuse mutualism between ants and a myrmecochorous plant.