Tawny crazy ants (TCA), Nylanderia fulva (Mayr), have recently received widespread attention in the regional, national, and even international media since public announcements were disseminated about their presence in Louisiana and Mississippi. The main concern associated with these unwelcome additions to the ant fauna of Louisiana is the fact that they establish large “supercolonies” containing multiple queens distributed among multiple nests and many millions of workers. This results in large, widespread infestations that may be difficult to control using methods focused on eliminating individual colonies, as occur with fire ants. Also, predicting exactly how TCA will impact the human and native fauna of Louisiana is difficult because newly established invasive species bring an element of ecological uncertainty when they occupy new landscapes and habitats.
What’s in a name?
Reporting the movement and first occurrences of the TCA has been confounded by the use of different common and scientific names to refer to a single species. Deyrup et al. (2000) reported the species from south Florida, where it has been established for many years under the scientific name Paratrechina pubens
Arrival in Louisiana
Entomologists have been expecting this pest ant to arrive in Louisiana for the past several years from the adjacent counties in Texas and/or Mississippi. Therefore, it was no surprise when ants collected in Calcasieu Parish, Louisiana, were identified by LSAM diagnostician Victoria Bayless during June 2011. These represented the first record of this species in the state based on specimens submitted to the Louisiana State Arthropod Museum. But, as noted above, ants apparently representing this species were also present in West Baton Rouge Parish. Subsequent samples submitted to the LSAM from Ascension, Terrebonne, East Baton Rouge, and Lafayette Parishes have also been identified as TCA. Specimens submitted to the LSAM and identified as TCA are identical in appearance to samples of TCA from Florida provided by Anthony Pranschke (Sarasota County Mosquito Management Services), which included males that allowed positive identifications. Florida and Louisiana specimens are consistent with images of N. fulva males illustrated on the Ants of Mississppi website.
These records and recent anecdotal reports indicate that TCA is well established in south-central Louisiana, and it can probably be expected to spread across much of the remainder of the state, especially the southern one-half. In fact, Gotzek et al. (2012) suggested that the species is already much more widely distributed than currently reported. All reported occurrences involve infestations of multiple dwellings/buildings and yards. These reports are consistent with situations reported from both Texas and Mississippi. Wetterer and Keularts (2008) reported population explosions of hairy crazy ants on St. Croix, U.S. Virgin Islands that caused crop damage and death to small livestock (i.e., rabbits). Wetterer (2007) suggested N. pubens as a potential candidate species for the “plague ants” of Bermuda during the 19th century, and included a number of vivid and alarming quotes from early written accounts of the infestations. Reports that TCA are capable of displacing red imported fire ants may come as small consolation if infestations in Louisiana achieve levels recorded in these historical archives.
Correct identification of the causal organism is the first step in addressing any entomological problem. If you suspect you may have an infestation of these unwelcome new arrivals, you may submit samples to the Louisiana State Arthropod Museum for identification. Go to the LSAM website (www.lsuinsects.org) for submission instructions.
The species Paratrechina fulva and
Additional Online Resources
Excellent photographs of Nylanderia fulva may be found at MacGown’s (2012) Ants of Mississippi website.
For useful information about the species’ status in Texas and management strategies that may apply equally to Louisiana, see Texas A&M’s (2008) crazy ant webpage.
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Gotzek D, Brady S. G., Kallal R. J. , LaPolla J. S. 2012. The Importance of Using Multiple Approaches for Identifying Emerging Invasive Species: The Case of the Rasberry Crazy Ant in the United States. PLoS ONE 7(9): e45314. doi:10.1371/journal.pone.
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Zhao, L., J. Chen, W. Jones, and D. Oi. 2012. Molecular comparisons suggest caribbean crazy ant from Florida and Rasberry crazy ant from Texas (Hymenoptera: Formicidae: Nylanderia) are the same species. Environmental Entomology 41: 1008-1018.