Insectes Sociaux

, Volume 62, Issue 3, pp 335–349 | Cite as

Acromyrmex charruanus: a new inquiline social parasite species of leaf-cutting ants

  • C. RabelingEmail author
  • T. R. Schultz
  • M. BacciJr.
  • M. Bollazzi
Research Article


Social parasites exploit the colony resources of social species to secure their own survival and reproduction. Social parasites are frequently studied as models for conflict and cooperation as well as for speciation. The eusocial Hymenoptera harbor a diverse array of socially parasitic species with idiosyncratic life history strategies, but it is probably in the ants where social parasites are most speciose and have evolved the highest degrees of morphological and behavioral specialization. In the fungus-growing ants, a total of five obligate social parasites are known: four species are parasites of leaf-cutting ants and one species parasitizes a primitive fungus-growing ant species in the genus Mycocepurus. Here we describe a new species of socially parasitic leaf-cutting ant, Acromyrmex charruanus sp. nov., from Uruguay, and we report initial observations on the parasite’s life history as well as on the morphological and behavioral adaptations related to the inquiline syndrome. Our observations suggest that Acromyrmex charruanus is an obligate inquiline social parasite of the thatch-mound-building, leaf-cutting ant Acromyrmex heyeri. Acromyrmex charruanus appears to be tolerant of the host, producing sexual offspring in the presence of the A. heyeri host queen. Queens of A. charruanus appear to reproduce semelparously and sexual offspring are produced during the austral fall (February), which differs significantly from the mating biology of the host species, which reproduces during the southern-hemisphere spring (October–December). We suggest that the diametrically opposed mating seasons of parasite and host might be adaptive, allowing the parasite to avoid competition for resources with the host sexual brood. The morphological and behavioral adaptations of A. charruanus accord with characters observed to arise early during the evolution of other ant inquiline parasite species, and so far we have no evidence for the existence of a worker caste in A. charruanus. Further field studies and behavioral experiments need to confirm our first observations and explore A. charruanus’s behavioral ecology, evolution, and life history in more detail.


Leaf-cutter ants Fungus-growing ants Attini Social parasitism Inquilinism Acromyrmex Pseudoatta 



We gratefully acknowledge the Dirección General de Recursos Naturales Renovables for permission to conduct fieldwork in Uruguay. We thank Naomi Pierce for permission to conduct parts of this study in her laboratory at Harvard University. Sarah Callan and Amelia Harvey kindly assisted in the laboratory. Christian Rabeling was supported by the National Science Foundation (DEB-1456964), the Harvard Society of Fellows, and by the William F. Milton Fund from the Harvard Medical School. Ted Schultz was supported by the National Science Foundation (DEB-0949689, DEB-1456964) and the Smithsonian Competitive Grants Program for Science. Maurício Bacci Jr. acknowledges support from FAPSP (2011/50226-0) and CNPq (311562/2012-4 and 487639/2012-0). Martin Bollazzi is grateful to Daniel Ramírez from Cambium Forestal for facilitating access to field research sites.


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Copyright information

© International Union for the Study of Social Insects (IUSSI) 2015

Authors and Affiliations

  • C. Rabeling
    • 1
    Email author
  • T. R. Schultz
    • 2
  • M. BacciJr.
    • 3
  • M. Bollazzi
    • 4
  1. 1.Department of BiologyUniversity of RochesterRochesterUSA
  2. 2.Department of EntomologyNational Museum of Natural History, Smithsonian InstitutionWashingtonUSA
  3. 3.Center for the Study of Social InsectsSão Paulo State UniversityRio ClaroBrazil
  4. 4.Section of Entomology, Faculty of AgronomyUniversity of the RepublicMontevideoUruguay

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