Invasive Ants

Two species of invasive ants have moved into some parks, damaging park facilities and harming wildlife:

Identifying the ants

An infestation involves potentially millions of ants with no noticeable nest mounds. They move very quickly and erratically. They may form trails going up trees and into buildings.

If you see ants exhibiting these types of behaviors in parks that aren’t listed above, please tell a ranger.

Living with invasive ants

These ants sometimes crawl onto people. They do not sting, but they can bite. They are especially troublesome for RVers, campers, and folks spending time outdoors.

If you encounter these ants when you visit a park, feel free to treat your own equipment but please do not treat park property. Although control is difficult, we are using best practices to prevent and treat these infestations.

Here’s how to minimize problems:

  • Practice good sanitation:
    • Make sure that your site and vehicle are always clean and free of trash.
    • Do not leave open containers of food or sweet drinks in or around your site or vehicle. Instead, keep these items in tightly-packaged containers.
    • Be sure to remove food debris from your vehicle.
  • Prevent the spread:
    • Do not bring potted plants to a park. Ants easily create colonies in loose potting soil and then hitch a ride to your next stop.
    • Purchase firewood at the park or from a local vendor. Only purchase enough firewood for your stay. Do not bring or take firewood with you.
    • Before leaving a Texas State Park, thoroughly inspect your vehicle, RV, camping gear, and other equipment for ants. If you see ants, please notify park staff immediately. We can offer guidance for treating infestations.

Problems with ants

Both tawny crazy ants and Argentine ants cause significant economic and ecologic problems.

These omnivorous ants can hurt wildlife. They out-compete native insects and disturb and prey upon other wildlife, including honeybees, small mammals and birds. Most importantly, they devastate local insect populations which are important foods for most native birds, bats, lizards and other wildlife.

Meet the ants

Tawny Crazy Ant

The tawny crazy ant (“Nylanderia fulva”) (formerly known as the Rasberry crazy ant) is originally from tropical South America (e.g., Columbia and Brazil). Experts believe these ants came to North America through shipping. The ants have been positively identified in more than 27 Texas counties. Their quick spread is largely due to people transporting materials (i.e., potted plants, landscaping material, hay or trash) that contain tawny crazy ant colonies.

Tawny crazy ants are relatively small (less than 1/5 inch long) and reddish brown, with large antennae and tufts of uneven hairs on the tip of their abdomens. Colonies consist of multiple queens capable of producing hundreds of thousands of workers.

Infestations involve potentially millions of ants that move very quickly and erratically, hence the name crazy ant. They do not sting but can inflict an uncomfortable bite. Tawny crazy ants are omnivorous, feeding on practically anything, including other insects, larger animals and sugary substances.

Tawny crazy ants do not create noticeable nest mounds like the red imported fire ant (“Solenopsis invicta”). Rather, these ants form colonies under or within places that hold moisture, such as rocks, stumps, soil, leaf piles, potted plants, mulch or compost piles. During cool weather, tawny crazy ants become less active. They resume their normal activities during warmer periods, with activity peaking during summer. Activity diminishes in the heat of the day in summer.

Argentine Ant

The Argentine ant (“Linepithema humile”) is native to Argentina and Brazil. Discovered in the United States for the first time in New Orleans in 1891, it has spread throughout the southern United States and several northern states. The species has been recorded in more than 30 counties in southern and eastern Texas and the Panhandle.

Like tawny crazy ants, Argentine ants are also relatively small (about 1/8 inch long). They vary in color from light to dark brown. The species is relatively hairless with distinguishing head characteristics that are only visible under magnification.

Argentine ants also form extremely large colonies with multiple queens. They nest in soil, under wood and slabs, in mulch, or in tree cavities and do not create noticeable nest mounds. They also do not sting, but they can inflict a mildly painful bite. During cold weather, these ants become dormant, and resume their normal activities during periods of warmth.

Ant Resources