Queens of the inquiline social parasite Acromyrmex insinuator can join nest-founding queens of its host, the leaf-cutting ant Acromyrmex echinatior

Abstract Queens of the inquiline social parasite Acromyrmex insinuator are known to infiltrate mature colonies echinatior and exploit host’s perennial workforce by producing predominantly reproductive individuals while suppressing host reproduction. Here we report three cases an A. queen having joined incipient colony that contained only founding host-queen her small symbiotic fungus garden. We conjectured 1:1 host-inquiline co-founding—a phenomenon has rarely been reported in ants—may imply presence may incur benefits increasing survival its colonies. observed queens neither foraged nor defended nest against intruders. However, interacted with a way could be consistent grooming and/or contributing eggs. These observations help explain why have maintained metapleural glands, even though they smaller than those queens, lost large foraging worker caste but not caste.