Like most other Pogonomyrmex spp. the Florida harvester ant has a psammophore (rows of long hair on ventral side of head) but it is poorly developed (Smith and Whitman 1992). The antennae are clubless with twelve segments. The thoracic dorsum has the sutures obsolescent or absent, and the thorax is not impressed between the masonotum and epinotum; The abdominal pedicel consists of two segments. The tibial spurs on the middle and hind legs are very finely pectinate.
The Florida harvester ant nests exclusively or by preference in sand. It requires open areas in which to build its nest and tends to nest in open woodlands or grassy areas (Haack and Granovsky 1990). Xeric hammocks are preferred. Many nests are found on lawns, around gardens, and in fire lanes (Van Pelt 1958). The mound is very slight and flattened with single or multiple entrances in the center and is from 30 to 60 cm in diameter. Unlike most other harvester ant species (Haack and Granovsky 1990), Florida harvester ant workers make no effort to clear vegetation from around the mound (Wheeler 1910). However, the mound is often covered with small pebbles or charcoal from burned areas (Smith and Whitman 1992).
The ant is vigorously active in rather low relative humidity (below 55 percent) and in high temperatures (35-40°C). Mating swarms usually occur in the afternoon after a rain (Haack and Granovsky 1990). Winged forms (reproductive adults) have been observed in the nests in May, and mating flights were recorded for June (Van Pelt 1958). Haack and Granovsky (1990) state that harvester ants swarm from June to October although the swarms are more common during August and September. Colonies are long lived and one was observed to last at least 19 years (Haack and Granovsky 1990). There is a single queen in each colony (Smith and Whitman 1992).
The ant harvests the seeds of many plants and stores them in the flat graneries of its nest which consists of many subterranean tunnels and chambers (Haack and Granovsky 1990, Tschinkel 2001). It not only collects seeds that have fallen to the ground, but also plucks them directly from the plants, husks them and deposits the chaff on the kitchen middens at the periphery of the mound. Seeds from the following plants have been identified from nests: ragweed, crab grass, small crab grass, rough buttonweed, sedge, Paspalium sp., poke weed, red clover, alfalfa, evening primrose, narrow leaf vetch and crotonweed.
The Florida harvester ant moves its nest periodically (an average of once every 234 days) in response to changes in microclimate resulting from shading due to overhanging vegetation. Pogonomyrmex workers of one colony will readily fight members of another colony of the same or different ant species and continued strife of this kind also results in colony movement (Smith and Whitman 1992).
A personal account of a sting episode by Wray (1938) is as follows: "Several ants stung me on the wrist, and after a few minutes an intense fiery pain began in this area which was about two inches in diameter. It turned deep red in color and immediately a watery, sticky secretion came out of the skin. This area became hot and feverish and the excruciating pain lasted all day and up into the night." At least one death, a child in Oklahoma, has been credited to stings by the red harvester ant, P. barbatus (Haack and Granovsky 1990).
In the event that management is necessary, see the following University of Florida recommendations:
Insect Management Guide for ants
Ant Trails: a Key to Management with Baits
Author: J.C. Nickerson, Florida Department of Agriculture and Consumer Services, Division of Plant Industry; and T.R. Fasulo, University of Florida
Originally published as DPI Entomology Circular 297. Updated for this publication.
Photographs: Lyle J. Buss, University of Florida
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-298
Publication Date: June 2003
Copyright 2003 University of Florida
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