Resumo. Rescue behavior among eusocial insects, particularly ants (Hymenoptera: Formicidae), is a remarkable cooperative interaction in which individuals risk their lives to save others without direct reward. This study reports the rescue behavior of the ant Ectatomma muticum Mayr, 1870 (Hymenoptera: Formicidae), which was freed from a trap set by a spider Neodiplothele Mello-Leitão, 1917 (Mygalomorphae: Barychelidae) in the paleodunes of the São Francisco River, in the Caatinga, northeastern Brazil. This is the first record of a rescue behavior in Ectatomminae and of a rescue involving an ant trapped in the silk of a trapdoor spider. Ectatomma muticum may represent a new model for the study of rescue behavior.