New World Ecitoninae, together with the Old World Dorylinae, are the
legionary ants, par excellence. Their colonies may reach enormous
size (up to 2.2xl07 for Old World Dorylus and
up to 106 for Eciton; Brian, 1965). Colonies
are nomadic. The bizarre queens lay enormous numbers of eggs at regular
intervals and when the brood reach a certain level of development,
the entire colony relocates to a new site. There is never a true nest,
as such, but only a temporary bivouac. The available information on
army ant life has been summarized by Gotwald (1982).
The Ecitoninae were, until
recently included within the Dorylinae, a group now considered to
be restricted to the Old World tropics and subtropics (Snelling, 1981b;
Gotwald, 1982). Wheeler and Wheeler (1985) have argued in favor of
lumping all the legionary ants back into the single subfamily Dorylinae
partly because that "... at least is well supported by larval evidence,"
even though they had earlier stated that larval characters (or their
lack) should not take precedence over adult characters. As additional
evidence they cited Kistner's (1972) conclusion that Neivamyrmex
and the Old World Aenictus shared a common ancestry
because of the relationship of their associated myrmecophilous staphylinids.
While Kistner's understanding of the staphylinids may be correct,
the conclusion regarding Neivamyrmex and Aenictus
does not necessarily follow. The value of such evidence is elusive.
Contrary "evidence" of a similar nature would suggest that the Old
and New World army ants have little in common since there are no known
myrmecophilous proctotrupoid wasps associated with the Old World forms,
while many are ecitophiles in the New World.
Gotwald and Kupiec (1975)
have suggested that the army ants may actually be triphyletic, based
on an analysis of geographic, morphological, and behavioral characteristics.
Their three lineages consist of the Cheliomyrmecini + Ecitonini in
the New World and two Old World groups, Dorylini and Aenictini. They
specifically reject that Aenictini and Ecitonini are more closely
allied to each other than either is to any other lineage; their morphological
similarities are presumed to be convergent.
The systematics of the New
World army ants has been fairly stable since the massive revision
by Borgmeier (1955). The few species described since 1955 are mostly
included in the keys by Watkins (1976). Watkins (1988) presented
a key to those army ants known to occur in the vicinity of Chamela,
The three genera Eciton,
Neivamyrmex, and Nomamyrmex should probably
all be recombined to form a single genus, Eciton. While
it is true that these genera are separable by the features cited in
the key cited below, the characters are trivial. Genera should be
based on characters of a more fundamental nature and on more such
characters than can be advanced in support of these genera. A detailed
study of character states in the numerous species of Ecitonini must
be made before any substantive conclusion can be reached; such a study
is beyond the scope of this paper.
The information presented
here is the result of an ongoing revisionary study of the New World
Ecitoninae, and should be considered preliminary. Although still in
the early stages this information is being presented here in the
hope that it will prove useful to other workers.
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• • •
Date of this version 21, July 2012
• • •
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