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The Hetaeriinae represents a phenomenal radiation of mostly myrmecophilous histerids. Of the above genera, about two-thirds are monotypic or contain a couple of very similar species. This is indicative of the enormous amount of morphological diversity in the group. Around 315 species are presently described, although there are likely three or more times this many actual species. Numerous generic level taxa also remain to be described. The bulk of Hetaeriinae diversity is found associated with the colonies of neotropical army ants (Ecitoninae). However, several other ant groups are known to host various Hetaeriinae, especially Attini, Formicinae (Formica, Lasius), and Myrmecinae (Pheidole, Solenopsis), and even some Nasutiterminae termites. A few genera occur outside of the Neotropical region, including the Holarctic Hetaerius (associated largely with Formica) and the exclusively Palearctic genera Satrapes, Sternocoelis, and Eretmotus.
Interactions of Hetaeriinae with their hosts have been studied in just a few cases. The most noteable are those of Wheeler (1908), Rettenmeyer (1961), Akre (1968), and Akre and Rettenmeyer (1968). These have together described the behavior of just a few genera, but they have illustrated a diversity of interactions, including ant-beetle grooming, phoresy, trophallaxis, and trail following by beetles. Yet there were also some clear differences in the beetles’ specific interactions. So while it appears that some hetaeriines function as fully integrated ‘symphiles’, or colony members, many have not achieved this level of integration. Additional studies of these fascinating relationships are badly needed.
The classification of Hetaeriinae remains rather unstable, given the great diversity of undescribed taxa. However, a fairly recent generic level revision of the Neotropical taxa (Helava, 1985) has clearly delimited the scope of the problem, and has provided some preliminary order. Studies of some of the more troublesome Neotropical groups continue (Tishchkin, unpublished data). The Palearctic taxa are in reasonably good shape taxonomically, with the genera Eretmotus and Sternocoelis recently having been revised (Yelamos, 1992, 1995).