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Subfamily MYRMICINAE
Tribe ATTINI

Pheidole moerens Wheeler, 1908

Caribbean big-headed ant

Uploaded, 2009; updated 22 February 2016
Author: Joe A. MacGown

Pheidole moerens, full face view of a major worker (Hancock Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a minor worker (Hancock Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, dorsal view of a minor worker (Hancock Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens major worker - head
Pheidole moerens major worker side view
Pheidole morens major work - side view
Pheidole moerens, full face view of a major worker (Lauderdale Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a major worker (Lauderdale Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a major worker (Lauderdale Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, hypostomal teeth of a major worker (Lauderdale Co., MS) (photo by Joe A. MacGown )
Pheidole moerens, dorsal view of petiole and postpetiole of a major worker (Lauderdale Co., MS) (photo by Joe A. MacGown )
Pheidole moerens, full face view of a male (Hinds Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, full face view of a male (Hinds Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a male (Hinds Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, dorsal view of a male (Hinds Co., MS) (Hinds by Joe A. MacGown & James Lewis)
Pheidole moerens, full face view of a dealate queen (Forrest Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a dealate queen (Forrest Co., MS) (photo by Joe A. MacGown & James Lewis)
Pheidole moerens, lateral view of a dealate queen (Forrest Co., MS) (photo by Joe A. MacGown & James Lewis)

Introduction
The genus Pheidole has been described as 'hyperdiverse" by Wilson (2003) in large part by the abundance and diversity of the genus, especially in the Neotropics. Workers in this genus have discrete major and minor castes, with the major workers having greatly enlarged heads. In the southeastern US, 21 named species are known to occur and at least one undescribed species is known from the region. In the Southeast, members of this genus can be found in all terrestrial habitats from fine sandy localities bordering creeks to hard-pan dirt in open area beside roadways to inside rotting wood in natural forested habitats. Both major and minor workers have 12-merous antennae (including scape and pedicel) that terminates in a 3-merous club; waist with both petiole and postpetiole, and atrophied sting. Many species possess propodeal spines, although a few do not. Majors are distinctive with their hugely enlarged heads (proportional to the body), which may be as wide or as long as the mesosomal length, and by the large mostly edentate mandible. Minor workers are much smaller than majors and often have dramatic physical differences. Queens are similar to major workers, except the heads are not proportionally enlarged as compared to the body, eyes are proportionally larger to the head than with workers, ocelli are present, overall are typically larger than both minor and major workers, and have enlarged thoracic regions to accommodate wings. Males are quite different in appearance from both workers and queens being somewhat wasp-like with beaded 13-merous antennae, greatly enlarged eyes (eye length may be half of more of the head length), reduced mandibles, enlarged ocelli that bulge from posterior margin of head, and with proportionally large wings.

Pheidole moerens is an introduced species that is now very common in southern Alabama and Mississippi (as well as Florida and Louisiana). It seems to prefer nesting in rotting wood, especially logs found laying on the ground, or in the soil just under rotting wood.

Taxonomic History (Bolton 2016)
Pheidole moerens Wheeler, 1908: 136, pl. 12, figs. 22, 23 (s.w.) PUERTO RICO. Neotropic. "Culebra; Porto Rico." AMNH, MCZC.  Wheeler & Wheeler, 1972: 244 (l.). Senior synonym of Pheidole moerens dominicensis: Naves, 1985: 65; of Pheidole moerens creola: Wilson, 2003: 461.

Identification
Minor Worker: Syntype measurements (from Wilson 2003): HW 0.42mm, HL 0.48mm, SL 0.44mm, EL 0.06mm, PW 0.26mm. Measurements of MEM specimens: HW 0.44–0.47mm, HL 0.49–0.51mm, SL 0.42–0.43mm, EL 0.08–0.10mm, ML 0.67–0.74mm, SPL 0.08–0.10mm, PetW 0.13–0.14mm, PpW 0.18–0.22mm, PronW 0.42–0.45mm (n = 5). Overall reddish brown to dark brown with gaster sometimes darker brown than the rest of the body; legs orangish brown. Head slightly longer than wide; foveolate, with rugulae present from anterior margin of head (including clypeus) to just posterior of eyes (occasionally extending almost to posterior margin of head on sides of head); and with limited, loose rugoreticulation between eye and frontal carina; scattered semi erect to erect, flexuous, somewhat thickened setae scattered over the entire surface of head and mandibles, similar setae present on antennal scapes. Antennal scape length approximately the length of the head. Promesonotum fused, in profile dorsum appearing as a continuous arced shape before; propodeum distinctly set below level of promesonotum; metanotal groove prominent; propodeal spines present, triangular, slightly upturned; entire mesosoma foveolate; mesosomal dorsum with scattered flexuous setae of varying lengths, more numerous on promesonotum. Petiole about twice as long as wide (dorsal view), petiole pedunculate, node raised, conical in lateral view, almost circular in dorsal view; sides of petiole foveolate, dorsum shiny. Postpetiole about as wide as long (dorsal); appearing circular in both lateral and dorsal views; some foveolate sculpture present posterolaterally, remainder shiny. Scattered elongate, flexuous setae present on both waist segments. Gaster smooth and shiny, lacking obvious sculpture; with scattered elongate, flexuous setae that are directed posteriorly present.

Major Worker: Syntype measurements (from Wilson 2003): HW 0.84mm, HL 0.90mm, SL 0.46mm, EL 0.10mm, PW 0.40mm. Measurements of MEM specimens: HW 0.80–0.84mm, HL 0.86–0.91mm, SL 0.44–0.46mm, EL 0.11–0.13mm, ML 0.52–0.55mm, SPL 0.05–0.06, PetW 0.08–0.09mm, PpW 0.11–0.13mm, PronW 0.28–0.31mm (n = 5). Head, mesosoma, waist, and antennae dark reddish brown; gaster darker brown to somewhat infuscated at base to darker brownish black posteriorly; legs lighter, orangish brown. Head large, almost as wide as long; posterior margin of head deeply concave, corners of head strongly rounded; length of antennal scapes about half of head length; eyes small, placed below midline of head; five hypostomal teeth present, mid tooth wide and short, inner and outer teeth stout triangular; posterior corners of head shiny, lacking sculpture, remainder of head with strong longitudinal rugae and some rugureticulation between eye and frontal carina, spaces between mostly shiny; clypeus and mandibles mostly lacking sculpture; frontal triangle prominent, shiny; entire head with scattered, but regular short, erect setae, mostly directly anteriorly and away from head on and near margins, but setae located on central portion of head directed toward midline. Promesonotum almost continuous in lateral view, but usually with distinct promesonotal groove; strong metanotal groove present; propodeum set distinctly below level of promesonotum; propodeal spines strong, somewhat finger-like, directed upward and slightly posteriorly; propodeal spiracle circular. Sides and dorsum of mesosoma foveolate, transverse carina present on dorsum of pronotum, a few weak carina present on mesopleura and sides of propodeum. Petiole about twice as long as wide (dorsal view), petiole pedunculate, node raised, conical in lateral view, almost rounded rectangular in dorsal view; sides of petiole foveolate, dorsum shiny. Postpetiole wider than long in dorsal view, node elliptical; some foveolate sculpture present posterolaterally, remainder shiny. Scattered elongate, flexuous setae present on both waist segments. Gaster smooth and shiny, lacking obvious sculpture; with scattered elongate, flexuous setae that are directed posteriorly present.

Queen: Measurements of MEM specimens: HW 0.81–0.90mm, HL 0.74–0.83mm, SL 0.45–0.49mm, EL 0.24–0.27mm, ML 1.16–1.22mm, SPL 0.08–0.11mm, PetW 0.23–0.25mm, PpW 0.37–0.40mm, PronW 0.71–0.75mm, FWL 3.80–4.20mm (n = 5). Overall, queens are about 4.0 mm in total length. Head (including mandibles and antennae), mesosoma, and waist dark reddish brown; gaster dark brownish black; legs orangish brown; and winds hyaline with dark stigma. Head widest posteriorly before gradually diverging anteriorly, posterior margin widely concave; eyes large, length of eye less than the distance between eye and posterior edge of head; ocelli conspicuous; frontal triangle obvious, with rugae from head extending through it; antennal scape length about 2/3 the head length; entire head in full face and lateral view with strong longitudinal rugae present, with transverse rugae on posterior region of head and between eye and frontal carina forming a rugoreticulate pattern, spaces between rugae shiny in mid region of head (full face view) and foveolate laterally from the approximately the edge of the frontal carina to margins of the head; entire head with numerous scattered erect setae with setae on sides of head directed posteriorly away from the head and setae on central region of head directed toward midline of head; scapes with numerous erect setae. Pronotum with strong sculpture varying from rugulate to rugoreticulate; mesosoma with numerous short, semi erect curved setae that are directed posteriorly. Wings pale translucent hyaline with veins light brown; forewing venation of typical myrmicine type with pterostigma and costal, basal, subbasal, discal, and two submarginal cells closed; hindwing lacking jugal lobe and with costal, basal, and subbasal cells closed. Petiole about twice as long as wide (dorsal view), petiole pedunculate, node raised, conical in lateral view, almost rounded rectangular in dorsal view; sides of petiole foveolate, dorsum shiny. Postpetiole wider than long in dorsal view, almost twice as long as petiole, node elliptical; some foveolate sculpture present posterolaterally, remainder shiny. Scattered elongate, flexuous setae present on both waist segments. Gaster smooth and shiny, lacking obvious sculpture; with scattered elongate, flexuous setae that are directed posteriorly present.

Male: Measurements of MEM specimens: HW 0.59–0.60mm, HL 0.47–0.50mm, SL 0.12mm, EL 0.29–0.32mm, ML 1.12–1.16mm, PetW 0.15–0.16mm, PpW 0.20–0.23mm, PronW 0.65–0.68mm, FWL 2.80–3.04mm (n = 3). Overall, males are about 3.0 mm in total length. Head dark brown; mesosoma, waist and gaster light brown; antennae and legs pale yellow brown; and wings hyaline. In full face view head widest posteriorly measuring from outer edge of eye to eye, some hexagonal in shape (excluding eyes); mandibles present, reduced and with reduced dentition; eyes huge, more than half the length of head, placed on lower half of head; ocelli large and protruding; antennae beaded, scapes short and rectangular; clypeal area with some longitudinal carinae, remainder of head with strong, tightly woven rugoreticulation; numerous erect setae of varying lengths present on head; scapes with short, semi erect setae, funiculus dense pubescent; mesosoma, waist, and gaster mostly shiny, lacking sculpture, with numerous short, semi erect setae present. Wings pale translucent hyaline with veins light brown; forewing venation of typical myrmicine type with pterostigma and costal, basal, subbasal, discal, and two submarginal cells closed; hindwing lacking jugal lobe and with costal, basal, and subbasal cells closed.

This fairly small Pheidole species is very similar to P. floridana, especially the minors, however, the majors are much darker (a dark brown usually), have transverse striations on the pronotum (near the humeral area), have striations on the head extending more near the occiput, and have at least some rugoreticulation on the face between the eyes and frontal carina. Additionally, P. moerens seems to prefer nesting in rotting wood, whereas, P. floridana prefers nesting in sandy soil. Pheidole moerens is distinguished from Pheidole flavens by the broader smooth space of the occiput and feebler intercarinular foveolation on the head of the major, and especially by the darker color and more extensive sculpturing of the minor (Wilson 2003).

Biology and Economic Importance
This species is a common species in the Gulf Coast region being found from western Texas to eastern Georgia. We (MEM researchers) routinely find this species nesting in natural wooded habitats in rotting wood, especially logs found laying on the ground, or in the soil just under rotting wood, but also in suburban landscapes under boards, under bark of dead and live trees, at bases of oak trees and fence posts, along roots, under palm leaves, and inside wall crevices. The MEM has found this species in the following habitats and microhabitats: live oak and palmetto litter, slash pine litter, magnolia litter, leaf litter in hind dunes, chenier woodland, coastal savanna, mixed pine/hardwood forest near estuary, longleaf pine forest, pine oak forest near coastal dunes, longleaf pine/palmetto scrub, relic dune scrub, oak-pine sandhill, foredunes, sandy xeric scrub, longleaf pine/hardwood forest, a mixed oak/pine forest, hardwood forest, oak-hickory forest, riparian hardwood forest, open grassy area by highway, long roadside, under mulch at plant nursery, in house (swarming), along railroad tracks, and on palm trees at nursery. Similarly, Deyrup, et al. (2000) reported that this species occurs throughout Florida in a wide variety of habitats, and that it may have already partially replaced Pheidole dentigula and Pheidole floridana. Because colonies are often in rotten wood, in leaf litter, and in hollow twigs and nuts on the ground or occasionally arboreal, so P. moerens may compete for nest sites with native species in the genera Aphaenogaster, Camponotus, Nylanderia, SolenopsisHypoponeraStrumigenys, Brachymyrmex, and other species. It seems likely that dense populations of this species have some effect on native insects that serve as prey, but the diet of P. moerens has not been investigated in detail. However, in general, diet appears to be seeds, small arthropods, and scavenged human food (in urban areas).This species has been collected at hotdog bait, cookie bait, brown sugar/yeast bait, and peanut butter.

Colony sizes range range from small (a few hundred workers) to relatively large with thousands of workers with about five times as many minor workers as major workers. The individual chambers within a colony are small and usually are built with small soil or debris particles and have small openings. Colonies are monogynous, although several queens may start founding a nest. Before the first brood emerges, the dominant female typically kills the other queens. As with many other introduced species, P. moerens reproductives have a broad flight period, and the MEM has flight records from early May to late October. I have frequently collected P. moerens nesting side by side with the large introduced ponerine ant, Odontomachus haematodus. Unlike many of our native species of Pheidole, it is not unusual to see major workers of P. moerens foraging with minor workers.

According to Deyrup, et al. (2000), this species rarely enters homes. This statement likely reflects the activity of workers. The MEM has received numerous complaints of large numbers of winged reproductives swarming in homes causing a nuisance. Some homeowners were concerned that the dark colored females were swarming termites. As with other members of the genus, the sting is atrophied, and therefore this species does not pose a stinging threat to humans.

Distribution

Pheidole moerens is an exotic species native to the West Indies. It has become common both in natural wooded habitats and urban/suburban habitats along the Gulf Coast region in the US. At this time, the distribution appears to be limited to the southern part of the Coastal Plain.

Native range: West Indies (Wilson 2003)
Australian Region: Australia (Antweb.org data)
Eurasian Region: Saudi Arabia (Antweb.org data)
Nearctic Region
: Alabama, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Washington (MEM records and Antweb.org data)
Neotropical Region: Dominican Republic, Haiti, Honduras, Puerto Rico, Venezuela (Antweb.org data)
Pacific Islands Region: Hawaii (Antweb.org data)

Acknowledgments
Funding for the ant work being done by the MEM in Alabama and Mississippi is from several sources including the National Institute of Food and Agriculture, United States Department of Agriculture, under Project No. MIS-012040, the Mississippi Agricultural and Forestry Experiment Station at Mississippi State University, with support from State Project MIS-311080, NSF Grants BSR-9024810 and DFB-9200856, the Tombigbee National Forest (U.S. Forest Service), the Noxubee Wildlife Refuge, Mississippi Natural Heritage Program Research Grant, USDA Forest Service Agreement No. 08-99-07-CCS-010, the William H. Cross Expedition Fund, and primarily by the USDA-ARS Areawide Management of Imported Fire Ant Project. Additionally, special cooperation has been provided by State Parks, National Forests, National Wildlife Refuges, the Natchez Trace Parkway, and from various private landowners in both Alabama and Mississippi.

Literature Cited

Bolton, B. 2016.  Bolton World Catalog Ants. Available online: http://www.antweb.org/world.jsp. Accessed 9 February 2016.

Naves, M. A. 1985. A monograph of the genus Pheidole in Florida, USA (Hymenoptera: Formicidae). Insecta Mundi 1:53-90.

Wheeler, W. M. 1908. The ants of Porto Rico and the Virgin Islands. Bulletin of the American Museum of Natural History 24:117-158. 

Wheeler, G. C.; Wheeler, J. 1972. Ant larvae of the subfamily Myrmicinae: second supplement on the tribes Myrmicini and Pheidolini. Journal of the Georgia Entomological Society 7:233-246.

Wilson, E. O. 2003. Pheidole in the New World. A dominant, hyperdiverse ant genus. Cambridge, Mass.: Harvard University Press, [ix] + 794 pp.

Links

Antweb
Antcat
Antwiki