Neivamyrmex pilosus

In the United States males have been collected from June into August but most commonly during June and July.

Identification
Smith (1942) - The major worker is characterized by its color and sculpture; feebly produced, almost rounded posterior corners of the head; long, slender scape; strongly convex promesonotum; and the very distinctive ventral spine of the petiole. The male can easily be recognized by the shape of the mandibles and frontal carinae; large eyes and ocelli, the latter placed on a protuberance above the general surface of the head; length and form of the scape; smooth, concave area back of ocelli; pronounced occipital flange; the distinct longitudinal median groove where base and declivity of epinotum meet; the yellowish-brown body with yellowish wings and darker head, legs, and seventh gastric sternum.

Although all the specimens have most of the characters mentioned in the description, a number of the characters are very variable, these being the general robustness and shape of mandibles; length and shape of antennae; size and convexity of eye; width of space between frontal carinae; distance between inner border of eye and lateral ocellus; depth of body color; length of pilosity. The tooth on the superior border of the mandible may vary considerably in size and shape but is always prominent enough to attract immediate attention.

Distribution
United States: Arkansas and Mississippi west to southern Arizona; Mexico: border states south to Chiapas; south to Brazil and Paraguay.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Brazil, French Guiana, Guatemala, Guyana, Honduras, Paraguay, Peru, Suriname, Trinidad and Tobago, Venezuela.

Biology
Jack Longino: This is the most commonly encountered species of Neivamyrmex in Costa Rica. It is the only species routinely seen raiding during the day. The columns of black, shiny workers that are relatively uniform in size distinguish them from other diurnally raiding army ants. The workers have a strong foetid odor. I have often seen raiding columns ascending and descending canopy trees. Caches of prey brood may be found under bark flaps and under leaf litter along the columns. Prey brood are usually Crematogaster or Azteca. These observations suggest that N. pilosus is a specialist on arboreal ants.

While collecting in Venezuela, I once observed a column of N. pilosus raiding Azteca in a Cecropia peltata tree that had been pushed over by logging activity.

Males are common at lights. The ALAS project carried out an 18-month program of sampling using blacklight traps. Males of N. pilosus were only obtained in the months of March, April, and May. These are the months of late dry season to early wet season.

Nomenclature

 *  pilosus. Eciton pilosa Smith, F. 1858b: 151 (w.) BRAZIL. Reichensperger, 1939: 297 (q.); Smith, M.R. 1942c: 544 (m.); Wheeler, G.C. 1943: 331 (l.); Wheeler, G.C. & Wheeler, J. 1984: 273 (l.). Combination in E. (Acamatus): Emery, 1894c: 183 (in key); in E. (Neivamyrmex): Smith, M.R. 1942c: 544; in Neivamyrmex: Borgmeier, 1953: 8. Senior synonym of angustius, porrectognathum: Borgmeier, 1955: 361; of beebei: Snelling, G.C. & Snelling, R.R., 2007: 488.
 * angustius. Eciton pilosum var. angustius Forel, 1909a: 256 (w.) PARAGUAY. Combination in Neivamyrmex: Borgmeier, 1953: 8. Junior synonym of pilosus: Borgmeier, 1955: 361.
 * beebei. Eciton (Acamatus) pilosum var. beebei Wheeler, W.M. 1921d: 312, fig. 7 (w.m.) GUYANA. Combination in Neivamyrmex: Borgmeier, 1953: 19. Subspecies of pilosus: Borgmeier, 1953: 19; Borgmeier, 1955: 373. Junior synonym of pilosus: Snelling, G.C. & Snelling, R.R., 2007: 488.
 * porrectognathum. Eciton (Acamatus) porrectognathum Borgmeier, 1933d: 167 (m.) BRAZIL. Combination in Neivamyrmex: Borgmeier, 1953: 5. Subspecies of pilosus: Borgmeier, 1953: 5. Junior synonym of pilosus: Borgmeier, 1955: 361.

Worker
Smith (1942) - Major. Length 4.6 mm.

Head approximately as broad as long; with convex sides. Posterior border visible only from above, emarginate, forming weakly produced or very feebly angulate posterior corners. Eye ocellus like, flat, small but distinct. Mandible triangular; superior border without a basal booth; masticatory border with several small, irregular teeth on the upper half. Antennal scape extending at least its greatest width beyond posterior border of eye; funiculus not noticeably robust; segments 1 to 4 inclusive distinctly longer than broad. Frontal carina not forming a flange in front of antennal socket. Dorsal surface of promesonotum, in profile, forming a rather strong, continuous arch which occupies approximately two-thirds length of thorax; greatly elevated above epinotum and meeting epinotum in a distinct but shallow constriction. Basal and declivous surfaces of epinotum subequal in length and meeting in a bluntly rounded, obtuse angle. Pronotum without an apparent transverse carina. Thorax, from above, compressed and narrowest in region immediately posterior to front coxae. Mesothoracic spiracle appearing as a faint depression very slightly above most posterior extension of pronotum over mesonotum; meta thoracic spiracle appearing as a somewhat larger depression in meso-epinotal suture and anterior to the very large, slitlike epinotal spiracle. Petiole with a very characteristic, acute, ventral spine directed posteroventrad. Petiolar node approximately one-eighth longer than broad, with at least one-third of the dorsal surface sloping anteriorly; posterior half slightly wider than anterior half, and with subparallel sides. Postpetiolar node distinctly broader than petiolar node, broader posteriorly than anteriorly, with rounded sides and feebly rounded anterior and posterior ends.

Mandible subopaque, with longitudinal striae and scattered piligerous punctures; pronotal collar with delicate granulate shagreening which causes this area in some lights to appear slightly subopaque; meso- and metapleura, most of sides of epinotum, and meso-epinotal constriction granulate-rugulose, and subopaque; sides of petiole and postpetiole with faint granulate shagreening, subopaque. Remainder of body and appendages smooth and shining except funiculi and tarsi. Head with small, scattered, sparse, piligerous punctures; dorsum of thorax, petiole, and postpetiole with larger and coarser, but sparser punctures

Hairs yellowish to grayish, fairly abundant, variable in length.

Color highly variable, ranging from almost uniform brown through brownish black to almost black, with antennal sockets, funiculi, tibiae, tarsi, and tip of gaster lighter. Often there are traces of infuscation on the head and thorax.

Male
Smith (1942) - Length 12-13 mm.

Head one and three-fourths to one and nine-tenths times as broad as long. Eye large, convex, protuberant. Ocelli large, placed on prominent protuberance above general surface of head, the summit of protuberance concave. Space between inner border of eye and lateral ocellus less than one-half diameter of lateral ocellus. Frontal carinae converging posteriorly, with sharp lateral borders and a deep median groove. Antenna of variable length; scape not remarkably stout, approximately as long as combined length of first 4 funicular segments; funicular segments 3 to 5 inclusive broader than others, thus causing the funiculus to appear tapering from base toward apex. Clypeus distinctly excised. Mandible slender, median section of inferior border straight or faintly excised; superior border with gently convex to angular protuberance, anterior and posterior to which there is a distinct excision. The large eye occupies all of side of head except a small area between it and base of mandible, and a much larger area posterodorsad of eye. Region of head posterior to ocelli, in profile, smooth, concave, with well-defined, reflexed, occipital flange. Head, from above, with well-rounded posterior corners which merge into eyes without forming perceptible angles or protuberances. Thorax strongly projecting above head. Mesonotum with well-defined anteromedian and parapsidal lines. Epinotum with a distinct, longitudinal, median groove where base and declivity meet; declivity concave. Tarsal claws not toothed or faintly so. Dorsal surface of petiole, in profile. with convexity originating very far posteriorly. Gaster elongate, moderately slender. Intermediate tooth of seventh gastric sternum short and usually blunt. Paramere, in profile, roundly pointed at apex, ventral border angulate, dorsal border with a tooth-like lobe and a membranous plate extending between tooth and base of paramere.

Head, legs, and anterior border of each gastric segment smooth and shining; remainder of body somewhat less shining, especially funiculi and thorax. Hairs yellowish, short, dense, and rather appressed on parts of the body; longer and sub erect to erect on head, legs, and venter of petiole.

Head, legs, and seventh gastric sternum darker than remainder of body, which is yellowish brown to brown. Wings distinctly yellowish with light-brown or yellowish-brown veins and stigma.

Type Material
Smith (1942) - British Museum of Natural History. Villa Nova, Brazil.

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