Biology and Identification
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The pyramid ant is a small ant about 1/8inch (3.5 mm) in length and has one node on its pedicel. Pyramid workers are all the same size. The key identifying character is the pyramid-shaped projection on top of the thorax. The antennae have 12 segments, and no antenna club is present. Two species of Dorymyrmex are encountered around structures. The most common species is D. pyrwnicus which has a reddish-black head and thorax and a black abdomen. The bi-colored pyramid ant, D. bicolor, has a red head and thorax and a black abdomen. Pyramid ants are found throughout the United States but are more common in the southern states.
Pyramid ants are generally "yard" ants that because they rarely enter or become pests in buildings. Infestations are generally just the result of foraging workers entering in search of food. Nests have not been reported indoors. In California, these ants have become less of a problem as they have been largely replaced by the Argentine ant around buildings. Pyramid ant colonies are usually small, containing only a few thousand individuals and a single queen.
The pyramid ant usually constructs its nests in soil in open, sunny, vegetation-free areas. As it excavates soil to construct galleries, the workers deposit the soil in a circular crater or mound around the entrance hole. The mound is usually from 2 to 4 inches (5 to 10 cm) in diameter. These mounds are often located near the nests of other ants, particularly those of harvester ants. Colonies also have been found under decorative stones and logs. These ants feed on other insects and are particularly fond of the honeydew produced by homopterous insects (aphids, mealybugs, and scales). Indoors, they will feed on a variety of foods but are particularly attracted to sweets. The workers move quickly and forage in strong, easily detected trails. Pyramid ants are rarely found foraging inside structures but may be common on porches, patios, and decks. New colonies of this species are formed by swarming, mating flights of winged reproductives. This flight normally occurs during the warmer summer months.
If workers of the pyramid ant are identified inside a home or other building, the inspection should be targeted to the building's exterior. If possible, the trails of workers inside can be traced back to their entry point. Inspections along the foundation may reveal ants entering through exterior cracks, such as weep holes, under doorways, and around windows. Crater-shaped mounds may be seen both near and away from the foundation.
Treating for Pyramid Ants with Talstar, Demon, Niban, Maxforce
Once colonies of pyramid ants have been located, they are quite easy to
eliminate. The colony is small and consists of a small chamber near the surface of the
soil, making easy access to the colony. Individual colonies of pyramid ants
be treated by drenching or spraying with an appropriately labeled residual liquid
insecticide such as Talstar Concentrate, Demon EC or Cypermethrin
EC 4 Oz. directly in the entrance hole using a compressed air sprayer. Just a
few ounces of insecticide solution are needed to treat each colony. Colonies under items
on the ground can be drenched with a few ounces of insecticide. For long-term
control, first drench each mound as mentioned above, then broadcast entire area to be
protected with Talstar Granules or Talstar Concentrate.
If the colony cannot be located, bait insecticides can be placed in areas where workers are active. Commercial baits containing a sweet food attractant should be effective but will take several days to be totally effective. The best outdoor baits for this job are Niban or Maxforce. For active, stubborn infestations, first use a good granular bait, wait 2 weeks, then broadcast Talstar.