DNA barcoding, i.e. the use of a 648 bp section of the mitochondrial gene cytochrome c oxidase I, has recently been promoted as useful for the rapid identification and discovery of species. Its success is dependent either on the strength of the claim that interspecific variation exceeds intraspecific variation by one order of magnitude, thus establishing a "barcoding gap", or on the reciprocal monophyly of species.

: Field data on associations of butterfly larvae with ants were collated for 435 species of the subfamily Lycaeninae to analyse patterns in the identity, diversity and ecology of attendant ants. Worldwide, members of at least fifty‐three ant genera from six subfamilies associate with Lycaeninae larvae. All these ant genera also forage for other liquid carbohydrate food sources. Species of Crematogaster and Camponotus constitute by far the most important ant associates of Lycaeninae larvae. Diversity of butterfly–ant associations, as measured by Hurlbert rarefaction, is highest in the Oriental, Australian and Nearctic faunal regions, and lower in Africa and the Palaearctic. The Neotropical region could not be assessed separately due to paucity of data. Multiple regression analyses revealed that the number of Lycaeninae species associated with a particular ant genus in a facultatively mutualistic manner is largely determined by the ecological prevalence and geographical distribution, but does not correlate with species richness, of an ant genus. This opportunism is suggested to be the key variable supporting the geographically and taxonomically widespread occurrence of ant–caterpillar mutualism in the Lycaeninae. Obligate interactions are much more specific and almost exclusively involve ecologically dominant ants with long‐lived colonies. Neither species richness nor geographical distribution of an ant genus are significant predictors. In such associations, the role of ants shifts from visitors to hosts, and patterns of host use and specificity resemble those known from inquiline ant guests.