Living underground: first record of myrmecophily in a species of tarantula (Mygalomorphae: Theraphosidae: Catumiri Guadanucci, 2004)

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Living underground: first record of myrmecophily in a species of tarantula (Mygalomorphae: Theraphosidae: Catumiri Guadanucci, 2004)

Abstract

Myrmecophily is widespread among arthropods but remains poorly documented in spiders, particularly in Mygalomorphae. Tarantulas (Theraphosidae) have not previously been shown to form true myrmecophilous associations, with existing records limited to anecdotal observations. Here, we provide the first robust evidence of myrmecophily in a tarantula, based on combined field and experimental data. Fieldwork in the Ñacuñán Biosphere Reserve (Monte Desert, Argentina) revealed that individuals of a species of Catumiri Guadanucci 2004 inhabit nests of the leaf-cutting ant Acromyrmex lobicornis Emery 1887. Of 45 excavated nests, 16 (35.5%) contained spiders, with a total of 69 individuals recorded. The presence of multiple developmental stages, including early instars cohabiting with adult females, indicates that reproduction and early development occur within ant nests. Additional observations documented spiders moving along ant foraging trails and entering nests without eliciting aggression. Behavioral experiments showed that this species exhibits high tolerance toward nestmate ants, characterized by frequent following behaviors and low avoidance. In contrast, interactions with non-nestmate ants or a non-associated species (Camponotus mus Roger, 1863) elicited increased avoidance. A non-myrmecophilous control tarantula (Grammostola inermis Mello-Leitão, 1941) showed strong avoidance and occasional predation on ants. These findings support the interpretation of Catumiri sp. as a facultative myrmecophile, using ant nests as refuges in a semi-arid environment. This study provides the first confirmed case of myrmecophily in Theraphosidae and suggests that such associations may be more widespread than previously recognized.

Cabral, M.E., Fernández Campón, F., Ledda, J. et al. Living underground: first record of myrmecophily in a species of tarantula (Mygalomorphae: Theraphosidae: Catumiri Guadanucci, 2004). Insect. Soc. (2026). https://doi.org/10.1007/s00040-026-01131-8