The Ecology of Some North American Dacetine Ants

Abstract

The tribe Dacetini is composed of a moderate number of unusual forms characterized by a tendency toward extreme reduction in the number of antennal segments, elaboration of the apparently predacious mandibles, and development of a wide diversity of types of bizarre cephalic hairs. It has recently been intensively revised by W. L. Brown (see 1948, 1949 for major changes), who finds that it is predominantly tropical and contains several large, abundant genera plus a quantity of small, very poorly known ones. Some of the larger genera have penetrated temperate zones and one at least (Smithistruma) has undergone considerable speciation there. Phylogenetic trends as outlined by Brown (1948 and in litt) include reduction in size, shortening of the mandibles, and a shift from an epigaeic to a hypogaeic mode of life. All of the forms found thus far in the United States belong to four dominant, relatively specialized genera. Strumigenys F. Smith is represented by one species, S. louisianae Roger, extending from tropical America into the southern states. Trichoscapa Emery is also represented by its single species T. membranifera Emery, a tropicopolitan tramp which has been collected frequently in the Gulf States. Quadristruma Brown is known at this time in the United States from a single record of Q. emmae (Emery) from Homestead, Florida; it has probably been introduced. Smithistruma Brown is represented by no less than 22 endemic and one possibly introduced species. These are found over the entire United States but are very scarce west of the Mississippi and in the extreme north. Even though it tends to be replaced by Strumigenys louisianae in local areas in the Gulf States, Smithistruma is by a wide margin the dominant genus in the United States.