Identification: Crazy ants, Paratrechina longicornis, are small (2-4mm), slender ants that appear to be all the same size. They are black or gray and sometimes have bluish reflections. These ants have very long legs and antennae and, upon closer inspection, will appear hairy (Pest Ants of Louisiana). These ants can be confused with rover and Argentine ants but are easily distinguished by their long legs and antennae.
Biology: This introduced species nests under objects in the yard, in potted plants, compost piles and in the soil. They will also nest in woodpiles (between logs or sheets of wood) and inside of signs. Colonies of crazy ants often have multiple queens, and they can form new colonies by budding. This means a queen can walk away with a complement of workers and start a new colony. They eat a variety of foods such as dead insects and honeydew secreted from Hemipteran insects, such as aphids and plant hoppers. The erratic scurrying of the workers gives them the well-deserved name, crazy ants.
Treatment: Look for foraging trails indoors and place liquid baits strategically. They will attend solid baits sporadically, particularly in the spring when they need protein for colony growth. During dry seasons, liquid baits are effective because the ants may come indoors in search of water. Use a contact insecticide as a barrier to prevent their entrance into the structure. Be sure to seal any cracks and crevices or other areas that might allow entry. Remove any vegetation that is in contact with the structure and might provide bridges ants can use to bypass barriers and enter the structure. Try to find the nests and saturate with contact insecticide to suppress the population. Be persistent. The process of suppressing the ants inside the building can be a long one.
The LSU AgCenter and the LSU College of Agriculture