Neivamyrmex graciellae

This species was only recently found to occur in the United States. Its discovery in southern Arizona raises the possibility that this species, rather than Neivamyrmex melanocephalus, might be the worker caste of Neivamyrmex mandibularis. (Snelling and Snelling 2007)

Distribution
UNITED STATES: Arizona. MEXICO: Jalisco, Oaxaca.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Biology
Watkins and Coody (1986) - The Estacion de Biologia Chamela is a field station of the Instituto de Biologia of the Universidad Nacional Autonoma de Mexico. It has an area of 1400 ha and is located about two km from the Pacific coast in the state of Jalisco, at km 59 on the highway from Barra de Navidad to Puerto Vallarta. The topography is low hills and canyons without permanent streams. Average annual rainfall is 733 mm, and the dry season is from November to mid-June. The dominant vegetation is deciduous tropical forest generally less than 8 m in height.

Army ant colonies are relatively abundant in this area and numerous columns may be seen crossing the station's roads and trails at night. During June. 1984. we observed 36 colonies (10 species) including three colonies of Neivamyrmex graciellae as follows:

Colony No. W-305. Dr. Stephen H. Bullock. resident Investigador Associado called my attention to a swarm of ants on the steps of a sidewalk near the headquarters weather station about 8:00 a.m. on 9 June 1984. Upon examining this “disorganized” swarm, the nonphysogastric queen was discovered running about among several hundred workers including newly eclosed callows. A gardener was watering nearby flower beds and this may have forced the colony to emerge from a subterranean cavity. A small sample of workers and the queen were removed from the swarm and preserved. Two mites were attached to the queen's alitrunk. Columns of workers were observed in this general area for the next two days. While collecting the queen, I (J. F. W.) was stung several times on the hands and arms by the aroused workers. Having previously experienced the very mild stings of several other species of Neivamyrmex, I was greatly surprised by the severity of these strings. I experienced a strong burning sensation similar to that resulting from a fire ant (Solenopsis) sting at each point of insertation around which a welt one to one and one-half centimeters in diameter arose almost immediately. Although the burning sensation disappeared after a few minutes. red patches of skin were still visible after two hours.

Colony No. W-306. A weak raiding column was observed on the station’s paved entrance road about 500 m from the headquarters about 11:00 p.m. on 8 June 1984. The column did not contain callow workers and extended from a small hole near the center of the road and disappeared into a cavity under the edge of the pavement. A few of the workers were carrying captured ant larvae.

Colony No. W-324. A migrating column of workers including numerous newly eclosed callows was discovered about 4:00 a.m. on 17 June 1984. The column, about one cm wide, was crossing the din EJE Central road near the 1.000 m marker. Some workers were carrying their own colony brood of small larvae (about 1.0 mm long), and other workers were carrying ant larvae and pupae captured from other colonies. At 5:20 a.m., a moving “swarm” of workers about one m long and ten cm wide with the nonphysogastric queen running unaided near the middle appeared along the column. The queen and several hundred workers were collected and preserved. Sixteen mites were removed from the queen’s body.

Worker
The male caste is unknown.

Nomenclature

 *  graciellae. Eciton gracellae Mann, 1926: 97 (w.) MEXICO. Watkins & Coody, 1986: 257 (q.). Combination in Neivamyrmex: Borgmeier, 1953: 10 (spelling emended to graciellae). See also note in Borgmeier, 1955: 389.

Worker
Length 2.75-4 mm.

Head a little longer than broad, broadest in front of middle, sides moderately convex, posterior corners narrowly rounded, border shallowly concave. Eyes very distinct, situated a little behind the middle of front of sides. Mandibular blades finely and bluntly denticulate. Antennal scapes extending a little beyond the eyes, all funicular joints longer than broad. Thorax rather slender, in profile evenly convex. Epinotum on a lower plane than the promesonotum, its surface shallowly impressed at basal half, very feebly convex behind, twice as long as broad and one and one half times as long as the declivity, into which it very broadly rounds. Petiole in profile a little longer than high, convex above, with the antero-ventral spine strong, elongate, curved and acute at apex, extending backward; from above longer than broad, with feebly convex sides, postpetiole in profile as long as high and convex above; from above a little longer than broad, with nearly straight sides. Legs long, rather slender, claws simple.

Shining. Mandibles rather coarsely striate. Head and body sparsely, moderately, coarsely punctate, except on the impressed anterior portion of epinotum and on the meso- and metapleurre which are densely punctate and subopaque.

Fine, elongate, erect yellowish hairs abundant on head, body and appendages, on the gaster mixed with shorter and subappressed hairs.

Gaster dark brown to black, remainder bright brownish red.

Queen


Nonphysogastric. Length 16.7 mm. Reddish brown gaster with slightly lighter head, alitrunk, and petiole. Yellowish brown legs. Body surface smooth, except for setae-bearing punctations. Setae abundant, short, appressed on gaster, erect on all other surfaces.

Head. Frontal view (Fig. 1C): median length 2.1 mm; width 2.3 mm; upper surface slightly concave in middle; upper corners broadly rounded; sides almost straight; frontal depression forms a narrow triangle from c1ypeus to head middle; lower border of clypeus broadly concave. Each eye consists of a small yellow pigment spot without a distinct convex cornea, located laterally on upper one-third of head. Antennal scape gradually thickened distally; proximal width 0.15 mm; distal width 0.3 mm; length 1.1 mm. Antennal flagellum not thickened apically; length 2.4 mm; width 0.15 mm; 11 segments. Mandible slender, weakly curved inward, and with a slight convexity on inner median border; length 1.2 mm. Dorsal view (Fig. 1B): sides of head rounded; frons indented; occipital margin about one-half head width, moderately concave, with district outer corners. Lateral view (Fig. 1A): anterodorsum of head rounded; posterior surface almost straight; occiput narrow, slightly extended.

Alitrunk. Dorsal view (Fig. 1B): length 4.8 mm; gradually widened from pronotum to propodeum; greatest width 2.0 mm; all sutures indistinct. Lateral view (Fig. 1A): height at propodeum 1.5 mm; dorsum of promesonotum gradually rounded to an almost level propodeal surface which bluntly rounds into a steeply declining posterior surface; pronotal-mesopleural suture distinct up to mesothoracic spiracle; a distinct lamella extends from the orifice of metapleural gland anteriorly along lower border of propodeum; meso- and metathoracic spiracles very small (0.1 mm); propodeal spiracle oval and relatively long (0.4 mm); oririces of meso- and metapleural glands distinct; bulla of metapleural gland large and distinct in undried specimens. Length of hind leg 7.5 mm (coxa 1.2 mm; trochanter 0.2 mm; femur 1.7 mm; tibia 1.6 mm; tarsus: seg. one 1.2 mm, seg. two 0.5 mm, seg. three 0.4 mm, seg. four 0.3 mm, seg. five 0.4 mm). Apices of meta tibia and metatarsal segments one-four with stout spines. Claws without teeth on inner borders.

Petiole. Dorsum transversely concave in middle. Dorsal view (Fig. 1B): broadly trapezoidal with rounded corners; median length 1.0 mm; greatest width 2.1 mm. Lateral view (Fig. 1A): height of node 1.0 mm; spiracle prominent; anteroventral tooth large, triangular with blunt apex.

Gaster. (nonphysogastric, Figs. 1A,B,D). Elongate with triangular notch in apex of fifth sternite; length 8.9 mm; greatest width 3.2 mm; greatest height 2.4 mm.

Type Material
Ototonilco, Jalisco, Mexico. Cotypes.-Cat. No. 29045 U. S. N. M. Described from nine workers taken from a file running through the grass in an orange grove.

Etymology
Named in honor of Senorita Graciella Mercedes Maderiaga, the child who found them.