Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory
ENT-219-20
June 2020
Pavement Ants
(Tetramorium immigrans Santschi) Ryan S. Davis, Arthropod Diagnostician • Lori Spears, Cooperative Agricultural Pest Survey Coordinator • Austin Taylor, Entomology Assistant
Quick Facts •
Pavement ants are the most common pest ant in and around structures in Utah.
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Worker pavement ants are all the same size and have only one queen.
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Pavement ants feed on many foods, but prefer sweet and greasy foods.
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Occasionally, pavement ants will injure plants.
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Indoor problems with pavement ants are worst in spring and early summer.
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Indoors, manage pavement ants using baits coupled with habitat modification, cleaning, proper food storage, and exclusion.
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Outside, use habitat modification, exclusion, bait, and residual/nonresidual insecticides to manage pavement ants.
INTRODUCTION Pavement ants (Formicidae, Tetramorium immigrans) are northern Utah’s most common pest ant in and around homes and structures. Until recently, the pavement ant’s scientific name was Tetramorium caespitum, but recent genetic work has clarified that our common pest Tetramorium species in the U.S. is from Europe and has been given the name T. immigrans (Wagner et al., 2017; Zhang et al., 2019). Genetic variation among pavement ant populations in the U.S. is low and it is believed that current populations were derived from one or a few closely related colonies from Europe introduced into the northeastern U.S. about 200 years ago (Wagner et al., 2017; Zhang et al., 2019). The pavement ant derives its name from the habit of nesting in soil along edges or in cracks around pavement, patios, driveways, sidewalks, and foundations, but they can be found nesting almost anywhere soil is present. Indoors, they can occur in large numbers when they forage for food or crumbs that have fallen on the floor, or when winged ants are found emerging inside a home UPPDL, 5305 Old Main Hill, Logan UT 84322, utahpests.usu.edu
Fig. 1. (left) Swarm of pavement ant workers in spring (Ryan Davis, Utah State University). Fig. 2. (right) Two workers fighting (Ryan Davis, Utah State University).
or structure. They are attracted indoors by food, garbage and moisture, or swarm indoors when they nest in or near foundation cracks or voids. Pavement ants can also be abundant in gardens, and occasionally injure plants. They are found throughout the U.S. from the West Coast to the Northeast.
IDENTIFICATION Pavement ants are most commonly recognized by their habit of gathering in large groups near cracks in the pavement, concrete, etc., particularly in the spring, and by their small, volcano-shaped mounds of dirt they deposit around their nests. Workers are 2.5 to 3 mm (0.10 to 0.12 inch) in length and are dark brown in color (Figs. 1-3). Pavement ants have workers of a single size (monomorphic). These ants have two nodes, one pair of spines on the thorax, and a stinger, though the stinger is typically retracted into the gaster and not readily visible (Figs. 2 and 3). One distinguishing characteristic of this species is the heavy sculpturing on the head and thorax that forms parallel grooves (Fig. 4). These grooves can most easily be observed with the use of a hand lens or microscope.
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