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Citrus Pests


Southern fire ant


Scientific name


Solenopsis xyloni (Hymenoptera: Formicidae)

Other common names


California fire ant, cotton ant

Similar species


red imported fire ant, Solenopsis invicta

native fire ant, Solenopsis geminata
Heads of the workers of the southern fire ant, Solenopsis xyloni are not as disproportionately large as those of workers of Solenopsis geminata.



United States: Alabama, Arizona, California, Georgia, Kansas, Louisiana, Mississippi, Nevada, New Mexico, North Carolina, South Carolina, Tennessee, and Texas.

Worldwide: Mexico.

Native to the southern United States and Mexico.

Diagnostic characteristics

  • Build loose mounds near the bottom of tree trunks.
  • Yellowish-red head and thorax, black abdomen (gaster). They may also be completely orangeish-red or brownish-black.
  • 10-segmented antennae with a 2-segmented club.
  • Hairy abdomen.
  • Occur in underground nest, only seen when mound is disturbed.
  • Resemble adults with legs and antennae held close to body.
  • Initially appear white with black eye-spots.
  • Color of pupae darkens with age.
  • Occur in underground nest, only seen when mound is disturbed.
  • Four larval stages.
  • White, grub-like larvae.
  • Fourth instar larvae are the only stage capable of ingesting solid food.
  • Occur in underground nest, only seen when mound is disturbed.
  • White in color.
  • Difficult to see without magnification.


Citrus hosts

All Citrus species and their hybrids.

Non-citrus hosts

Not a direct pest but is disruptive in agricultural production.

Host damage

  • Feed on flowers.
  • Damage young, developing fruit.
  • Chew on the bark and cambium of young trees to feed on sap.
  • Can girdle and kill young trees.
  • Chew twigs of newly planted, young trees.
  • Chew off new growth.
  • May nest in and plug irrigation lines.
  • Indirectly harm citrus by protecting honeydew-secreting insect pests from natural enemies. This protection can disrupt biological control programs targeting honeydew-secreting insects and result in larger populations of pest species including scales, aphids, whiteflies, etc.
  • Shown to preferentially attack some parasitized pest species, resulting in disruption of biological control programs of pest species like the California red scale.



Mating flights are the primary means of ant colony propagation. Colonies generally contain a few large workers (major workers), many medium-sized workers (media workers), and a majority of small workers (minor workers). The three types of workers are all sterile females and serve to perform tasks necessary to maintain the colony. The queen (or queens) is the single producer of eggs. The diet of foraging workers consists of dead animals, including insects, earthworms, and vertebrates. Workers also collect honeydew and store seeds. Larvae are fed only a liquid diet until they reach the third instar. When the larvae reach the fourth instar, they are able to digest solid foods. Worker ants will bring solid food rich in protein and deposit it in a depression in front of the mouth of the larvae. The larvae will secrete digestive enzymes that break down the solid food and regurgitate it back to worker ants.



Identification of fire ants in the genus Solenopsis is difficult and requires evaluating a series of different-sized workers. In addition, members of this genus are known to interbreed.

The southern fire ant is a generalist predator. Therefore, the presence of the ant may be beneficial when consuming certain pest species. However, the southern fire ant is viewed as a pest based on other negative impacts they may have on agricultural operations.



Martinez-Ferrer, M.T., E.E. Grafton-Cardwell, and H.H. Shorey. 2003. Disruption of parasitism of the California red scale (Homoptera: Diaspididae) by three ant species (Hymenoptera: Formicidae). Biological Control 26(3): 279-286. (doi:10.1016/S1049-9644(02)00158-5).

Manaaki Whenua - Landcare Research New Zealand. 2012. Invasive ant threat: Solenopsis xyloni. Information sheet #29. (



Weeks, J.A., A.C. Hodges, and N.C. Leppla


Citrus Pests
Content last updated June, 2012