PSYCHE 
Vol. 76 June, 1969 No. 2 
A REVISION OF THE NEOTROPICAL DACETINE 
ANT GENUS ACANTHOGNATHUS 
(HYMENOPTERA: FORMICIDAE 
By William L. Brown, Jr . 1 and Walter W. Keimpf 2 
Introduction 
At the time it was last reviewed (by M. R. Smith in 1944), 
Acanthognathus contained three species: ocellatus, lentils and 
brevicornis, known from Central America and a few localities along 
the eastern edge of South America. In the present paper we are 
able to add three distinctive new species — one from the heart of 
Amazonia, one from the Pacific Slope of Colombia, and one from 
Southeastern Brasil; and a male of the genus is described for the 
first time. We present fragmentary observations on living colonies 
of A. rudis and A. ocellatus to confirm M. R. Smith’s surmise that 
the genus is predaceous, at least to some extent on Collembola. 
Acanthognathus is a very distinctive genus within the tribe Dacetini, 
to which it clearly belongs, and within which it is one of the two 
most primitive living genera (Brown and Wilson, 1959). The 
other primitive member is Daceton, containing a single spectacular 
species confined to hylaean South America (Wilson, 1962). Though 
Daceton and Acanthognathus workers share a number of primitive 
characters (antennal segments 11; palpal segments 5, 3>* compound 
eyes large; antennal scrobes absent; humeri armed), they are very 
different in size, habitus, and choice of nest site, and thus may have 
diverged a long time ago. Acanthognathus has the aspect of a genus 
that has begun a shift from epigaeic to cryptic foraging. Its retention 
of large eyes, multisegmented antennae and palpi, and long mandibles 
suggests that much of its foraging must still be done in the open, 
department of Entomology and Limnology, New York State College of 
Agriculture at Cornell University, Ithaca, New York 14850, USA. 
2 Convento de Sao Francisco, Caixa Postal 5,650, Sao Paulo, S. P., Brasil. 
Manuscript received by the editor January 2 , 1969 
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