Diversity of butterfly–ant symbioses in the neotropical genus Ectatomma (Formicidae: Ectatomminae)

Despite the extraordinary diversity of organisms associated with ants, few species or genera have been inventoried for the myrmecophilous communities they host. Here, we review the known information on Lepidoptera associated with the ant genus Ectatomma, based on: (a) extensive colony sampling and observations on six focal species (E. tuberculatum, E. brunneum, and four cryptic species of the E. ruidum species complex) over a period of 43 years in Mexico, French Guiana, and Colombia, (b) a follow-up of the available literature, and (c) an analysis of Ectatomma images from various photographic databases available online and direct observations in Brazil and Suriname. No lepidopteran species were found inside the nests, but a wide variety of facultative mutualisms were observed outside on plants bearing extrafloral nectaries and/or honeydew-producing hemipterans; however, around 15% involved a form of commensalism, with no direct physical butterfly–ant interaction. Various new associations, previously unnoticed, are reported, and we illustrate a new symbiotic association between Rekoa palegon and E. ruidum sp. 2 in Mexico. At least 29 lepidopteran species from 19 genera, belonging to four tribes in three subfamilies and three families, participate in 41 associations involving only 5 of the 18 known Ectatomma species, all 5 characterized by visiting liquid food sources on foliage. Specialized interactions with Ectatomma ants were only found in three Riodinidae species, while in Lycaenidae interactions were all facultative. A greater sampling effort is needed, including nocturnal sampling and studies on little-studied species of this genus, to obtain a comprehensive picture of the extent of Ectatomma–Lepidoptera interactions.