An ant known for some years as Nylanderia sp. nr. pubens (but apparently really N. fulva, see below) is an invasive species that has developed into a serious nuisance in the southeastern United States. A rapidly expanding range, explosive localized population growth, and difficulty controlling populations have made this ant a significant pest.
Nylanderia pubens (formerly known as Paratrechina pubens; LaPolla et al. 2010), the Caribbean Crazy Ant, was reported to be relatively common in southern Florida during the mid-20th century (the name "crazy ant" for this group of ant species is inspired by their quick and apparently erratic movements). Similar pest ants in Florida (and the Caribbean) have been tentatively referred to as N. pubens or N. sp. nr. pubens (i.e., similar to, but not necessarily actually the same species as, N. pubens).
In 2002, an explosive population outbreak of an ant in the genus Nylanderia was documented around Houston, Texas (in 2010 this ant was reported from Louisiana and Mississippi as well). These ants were morphologically similar to N. pubens and the closely related N. fulva. Because of taxonomic uncertainty, they were designated as Nylanderia sp. nr. pubens (Meyers 2008). In the popular media, this Texas ant was called the Rasberry Crazy Ant after Tom Rasberry, the pest control operator who discovered it in Texas. Subsequently, a molecular genetic analysis by Zhao et al. (2012) clearly suggested that the ants known as Raspberry Crazy Ants from Texas and Caribbean Crazy Ants from Florida belong to the same species. A broader taxonomic investigation by Gotzek et al. (2012) concurred with this finding. Importantly, however, Gotzek et al. also concluded that these Florida and Texas ants are in fact N. fulva, not N. pubens (and that previous Florida records of N. pubens, a species which now appears to be still limited to the Caribbean, may in fact have been N. fulva as well--and that N. fulva may have been the culprit in earlier historical ant outbeaks in the Caribbean attributed to N. pubens).
Invasive N. fulva are challenging pests. They often occur in tremendous numbers and display supercolony characteristics in which individual colonies do not exhibit mutual aggression toward one another. Individual colonies have multiple females, with nests typically found in a variety of outdoor habitats in rotting wood, in soil, in and under various types of debris, under bark, in potted plants, in vehicles, and in structures. In Texas, they are less active during cooler months, but populations grow rapidly in the spring and increase in size throughout the summer and fall. They are omnivorous, but appear to prefer sweet liquids especially, such as those produced by various hemipterous insects (aphids, mealybugs, scale insects, etc.) and nectaries of plants. They supplement their diets with arthropods and small vertebrates for protein.
The high densities of foraging workers in affected areas make day-to-day activities uncomfortable for humans. These ants do not sting, but are capable of biting. They have been found to displace both native and introduced ants, presumably producing cascading ecological effects as well. They also may cause wildlife to move out of infested areas. The direct economic impact of these ants can be substantial. Failures of electrical equipment have been attributed to large numbers of these ants, which short out circuits and clog switching mechanisms. In some cases, the ants have caused thousands of dollars in damage and repair costs. The range expands at an estimated rate of around 30 m per month in urban areas and around 207 m/yr in rural areas. In Colombia, N. fulva is considered a serious pest that has reportedly displaced native fauna and caused grassland habitats to dry out as a result of elevated hemipteran levels on plants. Beekeepers in Texas have reported that honey bee hives have been destroyed by this ant species, with the ants reportedly more interested in the bee larvae than in the honey. After killing or driving the bees away, the ants then used the hives for their own colonies.
Valles et al. (2012) initiated a genomic analysis to identify apparent virus equences from these invasive ants in Florida in the hope of identifying viruses that could be useful in controlling their populations.
More information on the Rasberry Crazy Ant is available from the TAMU Center for Urban and Structural Entomology.
- Gotzek, D., S.G. Brady, R.J. Kallal, J.S. LaPolla. 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.0045314
- 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 (1): 118-131.
- MacGown, J. and B. Layton. 2010. The Invasive Crazy Ant, Nylanderia sp. nr. pubens (Hymenoptera: Formicidae), reported from Mississippi. Midsouth Entomoogist 3: 44-47.
- Meyers, J.M. 2008. Identification, distribution and control of an invasive pest ant, Paratrechina sp. (Hymenoptera: Formicidae), in Texas. Ph.D. Dissertation, Texas A&M University, College Station, TX.
- Valles, S.M., D.H. Oi , F. Yu, X.-X. Tan, and E.A. Buss. 2012. Metatranscriptomics and Pyrosequencing Facilitate Discovery of Potential Viral Natural Enemies of the Invasive Caribbean Crazy Ant, Nylanderia pubens. PLoS ONE 7(2): e31828. doi:10.1371/journal.pone.0031828
- Zhao, L., J. Chen, W.A. Jones, et al. 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(4): 1008-1018. DOI: 10.1603/EN11287
Nylanderia fulva, also known as the Rasberry Ant or Crazy Tawny Ant is an emerging pest species in the Southern United States. It is a small, dull brown ant with abundant long acuminate hairs and plentiful pubescence. Morphologically, the worker caste is indistinguishable from N. pubens. The species was referred to as Nylanderia cf. pubens until molecular work determined its true identity. For a recent study of this species, see Gotzek et al. (2012).
Diagnosis of worker among Antkey species. Worker caste monomorphic. Antenna 12-segmented. Antennal club indistinct. Antennal scape length less than 1.5x head length. Eyes medium to large (greater than 6 facets); do not break outline of head. Dorsum of mesosoma with weakly impressed metanotal groove, but never with a deep and broad concavity; dull with dense overlapping pubescence. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion. Mesopleuron shiny, not dulled by dense pubescence (less than 25 hairs). Metapleuron with a distinct gland orifice. Middle and hind coxae same color as mesosoma, not a strongly contrasting pale white. Waist 1-segmented (may be hidden by gaster). Petiole upright and not appearing flattened. Gaster armed with acidopore. Distinct constriction not visible between abdominal segments 3+4. Gaster (especially first segment) with dense pilosity, giving it a dull appearance. Hairs long thick and produced in pairs. Pubescence uniformly dense across mesosoma. Macrosetae on mesosoma long, flexuous and acuminate, strongly tapering to a fine tip. Body color reddish brown.
Among other introduced and commonly intercepted Nylanderia species, N. fulva can be distinguished from N. flavipes, N. guatemalensis, N. vaga and N. vividula by the dense amount of pubescence on the dorsal surfaces of the promesonotum, mesopleuron and first gastral segment. Of the two remaining species (N. bourbonica and N. steinhelli) that have similarly dense pubescence in these regions, N. fulva is distinguished from the former by the more reddish brown color and the macrosetae which are long, flexuous and acuminate (versus moderate, stiff and blunt). Nylanderia fulva is easily distinguished from N. steinhelli by the color of the coxae which are uniform with the rest of the legs and body (versus strongly contrasting white), and by the mesosomal pubescence which is uniformly dense across mesosoma (versus uneven, becoming denser on dorsum, more sparse laterally on pronotum and mesopleuron). The worker caste is morphologically indistinguishable from N. pubens. The males can be separated by the following characters: (1) paramere apices are triangular and weakly sclerotized (yellow to slightly darker coloration) (versus apices rounded and well sclerotized (dark brown coloration) in N. pubens); (2) macrosetae originating from the paramere margin scattered and not fan-like (versus fan-like in N. pubens).
Relevance to Humans and Ecosystems
Nylanderia fulva is an emerging pest species.
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