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The Hairy Crazy Ant in Louisiana

Chris Carlton and Victoria Bayless

Update: 13 Feb. 2013. Just when we thought all this was settled, to solve the multiple common name problem, the Entomological Society of America Common Names Committee has put forward yet another common name, the "tawny crazy ant." This is a good lesson in why we should focus on scientific nomenclature in naming organisms. Settling the species identification of Nylanderia fulva should have been enough, since everyone can now simply use that name in a universally unambiguous way. But now common name enthusiasts risk muddying the picture further with another name for the same species. Will "tawny crazy ant" catch on, or will our Texas neighbors hold firm and declare their sovereignty with "Rasberry crazy ant?" Perhaps "hairy crazy ant" will persist at low levels like that neighborhood colony that you just can't quite exterminate. Stay tuned, but in the mean time, you ESA members may wish to voice your opinions on the subject via the contact information included in this link: http://www.entsoc.org/proposed-common-names

Hairy crazy ants (HCA), Nylanderia fulva (Mayr) or N. pubens (Forel), 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 HCA 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 HCA 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 Forel. The species was placed in the genus Paratrechina for many years. These and other authors referred to it under the common name “hairy crazy ant,” which is what the specific epithet “pubens” translates to in English. But the name “Caribbean crazy ant” also appears in the literature, after the presumed origin of the species in the Caribbean region. The species was transferred to the genus Nylanderia by LaPolla et al. (2010). More recent work by LaPolla's lab at Towson State University suggests that the species in the U.S. midsouth represents N. fulva (Mayr). Male reproductive ants are necessary to distinguish these two species. When the species was first reported in Texas during 2002 it was believed to represent an undescribed species and was referred to under the technical, though not taxonomically valid name, Nylanderia nr. pubens, meaning similar to N. pubens, but a different species. The common name “Rasberry crazy ant” was used to acknowledge Houston pest control operator Tom Rasberry (Meyers and Gold 2008). MacGown and Layton (2010) reported the species from Hancock Co., Mississippi, and referred to it as the “hairy crazy ant.” Aguillard et al. (2011) reported a population of supercolony forming crazy ants from West Baton Rouge Parish, Louisiana, but referred to them as Nylanderia nr. fulva. These West Baton Rouge Parish specimens are vouchered in the City of New Orleans Mosquito and Termite Control Board Teaching Collection (pers. comm., Kenneth Brown, BASF Pest Control Solutions). Nylanderia pubens was originally described as a subspecies of N. fulva, but was elevated to species rank by Trager (1984), and the two species are quite similar, with indistinguishable workers and similar habits, including the formation of enormous supercolonies (Aguillard et al. 2011). Meyers (2008) addressed the question of whether the Texas populations referred to as N. nr. pubens were distinct from the Florida and Caribbean populations of N. pubens. Based on morphological and molecular data, he concluded that these are the same species. These results were corroborated by recent molecular comparisons based on multiple genes (Zhao el al. 2012). But until recently, no one had examined the type specimens housed in the Natural History Museum, Geneva, Switzerland, to determine the morphological basis of the original names. This basic taxonomic work was recently completed at John LaPolla’s lab and this page will be updated when the results are published. 

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 as hairy crazy ants 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 and Terrebonne Parishes were also identified as HCA. The specimens submitted to the LSAM and identified as HCA are identical in appearance to samples of HCA from Florida provided by Anthony Pranschke (Sarasota County Mosquito Management Services). The Florida specimens have been identified as N. fulva based on comparison with illustrations provided on the Ants of Mississppi website.

These records indicate that the HCA has become established in at least two regions of Louisiana, and it can probably be expected to spread across much of the remainder of the state, especially the southern one-half. All reported occurrences involved 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 HCA 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 guests, you may submit samples to the Louisiana State Arthropod Museum for identification. Go to the LSAM website (www.lsuinsects.org) for submission instructions. Male reproductive ants are required for positive identification of N. fulva vs N. pubens, but for control purposes, that distinction is not necessary. According to the Ants of Mississippi website and recent work at Towson State, hairy crazy ants in the U.S. midsouth, including Louisana, represent N. fulva. Collections containing male specimens will be required for conclusive identification.

Summary

The species Paratrechina pubens became Nylanderia pubens and has been referred to using the common names "hairy crazy ant" and "Caribbean crazy ant." An unidentified "species" was called Nylanderia nr. pubens and referred to using the common names “Rasberry crazy ant” and "hairy crazy ant." Another incompletely unidentified "species" was called Nylanderia nr. fulva, implying similarity to Nylanderia fulva. Researchers in John LaPolla’s lab have conducted taxonomic work that will allow definitive species identifications when the results are published. Even with the use of modern search engines, homeowners seeking information about this pest may find it difficult to obtain accurate information about identification and control with so many names in use. Researchers, pest control operators, and homeowners should accurately identify pest species as the first step in developing rational, environmentally responsible pest management solutions.


workers

Fig. 1. Hairy crazy ant worker, dorsal and lateral, from Sarasota Florida (collector, Anthony Pranschke).

Queen

Fig. 2. Hairy crazy ant reproductive female, dorsal and lateral, from Sarasota Florida (collector, Anthony Pranschke).

male

Fig. 3. Hairy crazy ant reproductive male, dorsal and lateral, from Sarasota Florida (collector, Anthony Pranschke).

 

Additional Online Resources

Excellent photographs of adult N. pubens also may be found at MacGown’s (2011) 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. 


References

Aguillard, D., R. M. Strecker, and L. M. Hooper-Bùi. 2011. Extraction of super colonies of crazy ants from soil and wood. Midsouth Entomologist 4: 53-56.

Lapolla, J. S., S. G. Brady, and S. O. Shattuck. 2010. Phylogeny and taxonomy of the Prenolepis genus-group of ants (Hymenoptera: Formicidae). Systematic Entomology 35: 118-131.

MacGown, J. A., and B. Layton. 2010. The invasive Rasberry crazy ant, Nylanderiasp. near pubens (Hymenoptera: Formicidae), reported from Mississippi. Midsouth Entomologist 3: 441-447.

Meyers, J. M. 2008. Identification, distribution, and control of an invasive pest ant, Paratrechina sp. (Hymenoptera: Formicidae) in Texas. Doctoral dissertation. 177 pages. Texas A&M University, Texas.

Meyers, J. M. and R. E. Gold. 2008. Identification of an exotic ant, Paratrechinasp. nr. pubens(Hymenoptera: Formicidae), in Texas. Sociobiology 52: 589-603.

Trager, J. C. 1984. A revision of the genus Nylanderia (Hymenoptera: Formicidae) of the continental United States. Sociobiology 9: 49-162.

Wetterer, J. K. 2007. The vanished plague ants (Hymenoptera: Formicidae) of 19th century Bermuda. Myrmecologische Nachrichten 8: 219-224.

Wetterer, J. K., and J. L. W. Keularts. 2008. Population explosion of the hairy crazy ant, Paratrechina pubens (Hymenoptera: Formicidae), on St. Croix, US Virgin Islands. Florida Entomologist 91: 423-427.

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. In press.