Neivamyrmex nigrescens (Cresson)
Figures 36-39, 46, 48-50

     Labidus nigrescens Cresson, 1872:194; _. Cresson, 1887:250.
     Eciton nigrescens: Dalla Torre, 1893:5.
     Eciton sumichrasti: Mayr, 1886a:120. Mayr, 1886b:440 (in part, misident). Forel, 1899:27 (in part). Wheeler, 1900:563; fig. 1-3; o _. Wheeler and Long, 1901:160, note 2. Mann, 1926:99; _.
     Eciton (Acamatus) schmitti Emery, 1894:183; o. Emery, 1895:258; o. Forel, 1899:28. Wheeler and Long, 1901:161; fig. 1, 2b; _. Wheeler, 1908c:410; pl. 26 fig. 13; _. M. Smith,
1924:84. M. Smith, 1927:401-404. Borgmeier, 1936:59. G. Wheeler, 1943-331; pl. 2 fig. 29-33.
     Eciton (Labidus) nigrescens: Emery, 1895:261.
     Eciton (Acamatus) nigrescens: Emery, 1900:517, 525. Wheeler, 1908c:417; pl. 26 fig. 2; _ . Emery, 1910b:27. M. Smith, 1938:157; _.
     Eciton (Acamatus) sumichrasti: Leonard, 1911: ---
     Eciton (Neivamyrmex) nigrescens: M. Smith, 1942:551; fig. 4, 23; o _ _. Borgmeier, 1948:193. Creighton, 1950:66, 69, 73-74; pl. 12; o _ _.
     Neivamyrmex nigrescens: Borgmeier, 1955:293, 295, 297, 494-501; pl. 27 fig. 3; pl. 34 fig. 10; pl. 40 fig. 12; pl. 43 ig. 23-24; pl. 50 fig. 5, 13, 18; pl. 72 fig. 2; o _ _. Watkins, 1972:358-363; figs. 5-7, 12, 15, 20-22, 35-37, 50, 59, 62: o o o. Wheeler and Wheeler, 1973:37, 38-40; o _ _. Watkins, 1976:15, 22; pl. 6 fig. 12; pl. 9 fig 7-8; pl. 13 fig. 12; pl. 19 fig. 2-4; map 33; o _ _. Cokendolpher and Francke, 1990:12.

     RANGE: Coast to coast in southern United States; in the East, north to Virginia, Illinois, Iowa, Nebraska and Colorado; in the western United States, north to Utah, Nevada, and central California; Mexico.

     DESERT RECORDS. Map 11. Los Angles Co.: Barrel Springs Rd. & Pearblossom Hwy., 15 Aug. 1984 (G. C. Snelling; GCSCC, LACM, PSWC). Riverside Co.: Deep Cyn., 1300 ft., 20-27 June 1969 (S. Frommer, et al.; GJW); Red Cloud Cyn., ca. 8 mi SSW Desert Center (33.60°N 115.43°W, 2700 ft., 27 Aug. 1994 (G. C. Snelling, 94-085; GCSCC, LACM). Inyo Co.: Eureka Valley, 9 Apr. 1978 (DG et al; CDFA). Kern Co.: Lonetree Canyon, 6.8 mi S jct Hwy 14 & Randsburg Rd., 15 June 1970 (M. Wasbauer & F. Andrews; CDFA). San Bernardino Co..: Cima, 14 Apr. 1961 (CDFA).

     DISCUSSION. This common species evidently enters our area only marginally. It may be expected to occur in other areas, especially along stream courses running into the desert from chaparral habitats (such as Deep Creek, San Bernardino Co.; Big Rock Creek, Los Angeles Co.; Sentenac Canyon, San Diego Co.). The Deep Canyon habitat is described as Desert Riparian by Wheeler and Wheeler (1973).
      In Davis, California, Mallis (1938) noted nests in the cracks of sidewalks and in Texas nests were found under large flat stones (Wheeler and Long, 1901).
      Colonies which Wheeler (1900) studied consisted of "thousands" of individuals, while Schneirla (1958) estimated 150,000 to 250,000 workers per nest.
      Neivamyrmex nigrescens has a nomadic-statary cycle like Neotropical army ants such as Eciton. The nomadic phase of the cycle begins when pupae eclose to workers. The whole colony then moves along a trail, usually during night hours, capturing any insects they encounter and raiding the nests of other ant species encountered. Columns may be 90m long and are headed by scouts. The colony bivouacs before dawn, using natural cavities or nests of other species which they have pillaged. The following night they again move and raid. This nomadic cycle lasts for about three weeks or until the larvae in the colony (which they transport each night) begin to pupate. The statary phase then begins and the ants nest in subterranean cavities, either under stones or in abandoned ant nests for about 18 days (Schneirla, 1958). Raids continue but are less extensive than during the nomadic phase.
      New colonies of N. nigrescens are formed when "a daughter queen leaves the parental nest, accompanied by a number of workers. A mature colony is capable of producing a small number of females, some of which may be fertilized in the nest by their brothers, but this does not preclude mating outside the nest, or with males of other colonies. Since females are never winged, they can make no nuptial flight." (Smith, 1965). Watkins (1976) expressed the opinion that queens should not be collected from nests. Since colonies are monogynous, removal of the queen automatically means the death of the colony. He observed that "...less than one of every ten colonies produces new reproductives each year, and these reproductives from each colony form only one or two new colonies."
     Other ants form an important part of the diet of N. nigrescens. Mallis (1938) observed this species carrying larvae and pupae of Tetramorium caespitum (Linné), as well as click beetles, mayflies, water boatmen and crickets. Wheeler and Long (1901) found larvae of Solenopsis geminata (Fabr.) and three species of Pheidole, as well as dead carabid beetles, in nests they studied in Texas. Neece and Bartell (1982) noted the presence of an unidentified mites of the family Trachyaropodidae in colonies of N. nigrescens.The blind snake, Leptotyphlops dulcis, is able to follow the pheromone trails of N. nigrescens to locate columns and feed on the ant brood (Watkins et al., 1967). When the army ants attack the snake it forms a protective ball-like coil and smears a cloacal fluid on its body which discourages further ant attacks (Watkins et al., 1972).

      ASSOCIATED ARTHROPODS
     Several species of scuttle flies (Diptera: Phoridae) are known to parasitize adults of N. nigrescens. These include species in the genera Dacnophora, Cremersia (B. V. Brown, pers. comm.), and Xanionotum (Rettenmeyer and Akre 1968). The diapriid wasp, Ecitovagus gibbus Masner has been found as a parasitoid of N. nigrescens in southeastern Arizona (Masner 1977).
     Myrmecophilous Staphylinidae (Coleoptera) associated with this ant in areas other than California include: Microdonia laticollis Brues, M. nitidiventris Brues, M. occipitalis Casey, Ecitoxenidia brevicornis Seevers, E. brevipes Brues, Dinocoryna carolinensis Seevers, and Ecitonidia wheeleri Wasmann (Seevers 1965).
     Species in the carabid beetle genus Helluomorphoides are specialized predators on both the booty and brood of N. nigrescens in southeastern Arizona: "The beetles were observed running in army ant columns or standing off to the sides of the columns, behind rocks or beneath clusters of leaf litter. During their predatory activities, beetles ran along the trails in both directions, 'plowing' through the continuous two-way ant traffic. When a beetle of either species contacted a worker ant bringing booty back to her bivouac, the ant usually dropped the booty. On some occasions, if the booty was a larval or pubal individual of another ant species, the beetle immediately ate it and continued on the trail. On other occasions the betle picked up the dropped booty, left the raiding column, and proceeded to a nearby rock. There, the beetle quickly ate the larva or pupa, returned to the column, and resumed running along the trail." Beetles were observed to forcibly take booty from the ants. The beetles were also seen to feed on brood caches of the Neivamyrmex colony with which they became associated. Plsek, et al. (1969) reported their observations on behavior of another species of Hellomorphoides in the laboratory.

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