Neivamyrmex californicus

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Neivamyrmex californicus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Neivamyrmex
Species: N. californicus
Binomial name
Neivamyrmex californicus
(Mayr, 1870)

Neivamyrmex californicus casent0005330 profile 1.jpg

Neivamyrmex californicus casent0005330 dorsal 1.jpg

Specimen labels


Snelling and Snelling (2007) - This species appears to be primarily an ant of montane and foothill areas. Little is known about the feeding preferences of this species other than that it presumably attacks exclusively, or nearly so, other ant species. Ward (1999) lists the following as prey species of this ant: Veromessor andrei, Solenopsis molesta, Pheidole californica and Pheidole hyatti. One of us (GCS) observed a portion of a raid on a Solenopsis xyloni colony; the raid was well underway when it was discovered. It was apparently a violent one with S. xyloni vigorously defending its nest. Whether or not the raid was successful from the standpoint of N. californicus is unknown but the ground was littered with dead and dying of both species. The wingless phorid fly, Xanionotum hystrix Brues (Diptera: Phoridae), has been associated with a colony of N. californicus collected in San Diego County, California (J. H. Hunt, pers. comm.).


Smith (1942) - The worker of californicus can be distinguished by the slender petiole, which is distinctly longer than broad; the straight margin on the superior border of the mandible, lying between the basal tooth and the masticatory border; the rather small, somewhat indistinct eyes; the frontal carina not forming a distinct flange in front of the antennal socket; the shining head, promesonotum, propleura, postpetiole, and gaster; the reddish brown body with lighter gaster; and by the moderately abundant hairs of variable length, those on the scapes, dorsum of body, legs, and venter being unusually long and suberect to erect.

The worker can be distinguished from that of Neivamyrmex opacithorax by its more feebly sculptured and therefore more shining body, this being especially true of the promesonotum; generally longer and more erect hairs of the body; less distinct eyes; and usually lighter color. Eciton opacithorax was formerly considered a subspecies of californicus but was later raised to specific rank.

Watkins (1972) - Worker. Petiole distinctly longer than broad; head smooth or weakly reticulated; basal margin of mandible joining the cutting margin in a convex arc. Queen. Eyes distinct; petiole subquadrate, slightly broader than long, perpendicular anterior surface (in profile) forming a rounded corner with flat dorsal surface; posterodorsal corners of head rounded and not projecting; head and alitrunk very finely granulated; setae scattered over entire surface of gastric tergites; frontal carinae extending in front of antennal fossae.

Worker variation. Length (deflected head) 2.4-5.0 mm. Occipital corners vary from broadly rounded to slightly angular. Petioles vary from 1.3 to 1.8 times longer than wide. Although the petioles are usually similar in shape to those of Neivamyrmex nigrescens, one large worker (5.0 mm long) from La Jolla, Calif. (USNM) has an unusually broad petiole. The sculpture of the heads varies from smooth to thickly reticulated. The sides of the pronotum and mesonotum may be smooth, weakly reticulated, or deeply reticulated, with some granular areas; most of the reticular impressions are usually somewhat elongate oval. Some workers examined appear to be intermediate between calijornicus and nigrescens, but workers of both species can be separated from Neivamyrmex opacithorax by the shapes of the mandibles.

Keys including this Species


United States: California. Mexico: Baja California.

Distribution based on Regional Taxon Lists

Nearctic Region: United States (type locality).
Neotropical Region: Mexico.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb



The male caste is unknown.



The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • californicus. Eciton californicum Mayr, 1870b: 969 (w.) U.S.A. Watkins, 1972: 364 (q.). Combination in E. (Acamatus): Emery, 1894c: 182 (in text); in E. (Neivamyrmex): Smith, M.R. 1942c: 560; in Neivamyrmex: Borgmeier, 1953: 8. Senior synonym of obscura: Borgmeier, 1955: 517. See also: Ward, 1999a: 76; Snelling, G.C. & Snelling, R.R., 2007: 467.
  • obscura. Eciton (Acamatus) californicum var. obscura Forel, 1914d: 265 (w.) U.S.A. [Unresolved junior primary homonym of obscurum Forel, above.] Junior synonym of californicus: Borgmeier, 1955: 517.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.



Smith (1942) - Major. Length 3-4 mm.

Head scarcely longer than broad; narrowed posteriorly; posterior border emarginate, forming produced, but blunt, angular corners. Eye rather small, ocellus-like, not easily discernible. Mandible of same general shape as that of opacithorax. Scape moderately robust, approximately three and two-tenths times as long at broad; when fully extended backward noticeably surpassing posterior border of eye; funiculus not especially robust. Frontal carina not forming a distinct flange in front of antennal socket as in wheeleri and leonardi. Thorax,- from above, widest in region between fore coxae; promesonotum rather convex; a weak but distinct transverse carina on anterior part of prothorax. Epinotum clearly lower than mesonotum but not separated from it by a very distinct suture. Petiole, in profile, longer than high, convex above, with a blunt but definite anteroventral tooth. Postpetiole convex above, higher than long, highest posteriorly. Petiole, from above, slender, distinctly longer than broad, broadest posteriorly. Postpetiole subtrapezoidal, shorter but distinctly broader than petiole, and broader posteriorly than anteriorly.

Noticeably shining with the following exceptions: Mandibles, funiculi, meso- and meta pleura, epinotum, petiole, and tarsi, which are slightly subopaque.

Mandibles striate-punctate; meso- and metapleura, epinotum, and petiole with granulate shagreening. Head with sparse, scattered punctures. Dorsum of thorax and petiole with scattered, foveolate punctures, best seen only in certain lights.

Pilosity yellowish, moderately abundant, of variable length, suberect to erect. Antennal scapes, dorsum of body, ventral surface of gaster, and legs with sparse but very long, suberect to erect hairs.

Light to dark reddish brown, with distinctly lighter gaster.


Watkins (1972) - (Davis, Calif.). Nonphysogastric. Length (head not deflected) 11.1 mm. Head slightly wider than long, narrowed posteriorly; median length 1.6 mm; greatest width 1. 7 mm; sides convex; occipital corners rounded, and not projecting; occipital margin somewhat broadly “V” shaped, with concave middle. Eyes with distinct convex corneas, located near upper one-third of head. Inner margin of mandible strongly convex near middle, then gradually tapering to a sharp apex. Cutting margin of left mandible smooth, and of right mandible with irregular teeth. Frontal carinae rounded, with a deep median impression between them, and extending below antennal fossae. Scape thickened distally; length 0.9 mm. Flagellum not apically thickened; length 2.3 mm; segment 1 shortest, about as long as wide; 2-5 slightly longer than wide; 6-7 as long as wide; 8-10 slightly longer than wide; apical segment 3 times longer than wide, gradually tapering toward apex, and more than 2 times length of anteapical segment. Alitrunk length 3.2 mm; greatest width 1.2 mm at base of propodeum. Promesonotum rounded without a median impression from a dorsal view. Propodeum somewhat flattened, with a median longitudinal groove. Pronotum strongly narrowed anteriorly. Base of propodeum only slightly wider than mesonotum. Promesonotal and mesopropodeal sutures distinct. Promesonotum, in profile, convex and sloping anteriorly. Mesonotum and propodeum almost flat in profile. Dorsal surface of propodeum, in profile, more than 2 times length of sloping surface which forms a 45 degree angle with the dorsal surface at the mid-line. Petiole subquadrate, slightly wider than long, and elevated above the alinotum; length 0.85 mm; width 1.0 mm; height (including ventral projection) 1.1 mm; dorsal surface with a broad, shallow, longitudinal concavity; anterior, posterior and lateral borders, viewed dorsally, almost straight with rounded corners; flat dorsal surface, in profile, forming a rounded corner with perpendicular anterior surface; posterior surface of node perpendicular and forming a square corner with the dorsal surface; anteroventral projection large, somewhat conical with a broadly rounded apex. Gaster elongate; length 5.6 mm; greatest width 2.4 mm; apical segment gradually tapering with a deep, broad, triangular notch in apex of fifth gastric sternite. Length of metacoxa 0.7 mm, narrower and slightly longer than pro- and mesocoxae; length of metafemur 1.4 mm, meta tibia 1.4 mm, metatarsus 2.5 mm. Proximal tarsal segment 2 times length of segment 2; segment 4 shortest. Claws without teeth. Head, alitrunk and petiole very finely granulated between numerous coarse, shallow punctations which bear short, erect setae. Gaster smooth, except for scattered punctations bearing appressed setae which are more than two times length of setae on head and alitrunk. Color reddish brown with blackish mottling, especially on the gaster.

Type Material

Watkins (1972) - Syntype workers deposited in Natural History Museums of Vienna, Austria; Geneva, Switzerland; Genoa, Italy; London, England; and Borgmeier's Collection, Sao Paulo, Brazil (red label “cotype”).

Determination Clarifications

All previous out of state records (beyond California) believed to apply to this species have proven to refer to the recently recognized shiny headed form of Neivamyrmex nigrescens (Ward 1999). Watkins (1972) described what he believed was the queen of N. californicus, however recent reexamination of the specimen in question (Ward, 1999) has led to the conclusion that it too is a representative of the shiny form of N. nigrescens. (Snelling and Snelling 2007)


  • Borgmeier, T. 1953. Vorarbeiten zu einer Revision der neotropischen Wanderameisen. Stud. Entomol. 2: 1-51 (page 8, Combination in Neivamyrmex)
  • Borgmeier, T. 1955. Die Wanderameisen der neotropischen Region. Stud. Entomol. 3: 1-720 (page 517, Senior synonym of obscura)
  • Emery, C. 1894d. Studi sulle formiche della fauna neotropica. VI-XVI. Bull. Soc. Entomol. Ital. 26: 137-241 (page 182, Combination in E. (Acamatus) (in text))
  • Mayr, G. 1870b. Neue Formiciden. Verh. K-K. Zool.-Bot. Ges. Wien 20: 939-996 (page 969, worker described)
  • Smith, M. R. 1942c. The legionary ants of the United States belonging to Eciton subgenus Neivamyrmex Borgmeier. Am. Midl. Nat. 27: 537-590 (page 560, Combination in E. (Neivamyrmex))
  • Snelling, G. C.; Snelling, R. R. 2007. New synonymy, new species, new keys to Neivamyrmex army ants of the United States. In Snelling, R. R., B. L. Fisher, and P. S. Ward (eds). Advances in ant systematics (Hymenoptera: Formicidae): homage to E. O. Wilson - 50 years of contributions. Memoirs of the American Entomological Institute 80:459-550. PDF
  • Ward, P. S. 1999a. Deceptive similarity in army ants of the genus Neivamyrmex (Hymenoptera: Formicidae): taxonomy, distribution and biology of N. californicus (Mayr) and N. nigrescens (Cresson). J. Hym. Res. 8: 74-97 (page 76, see also)
  • Watkins, J. F., II. 1972. The taxonomy of Neivamyrmex texanus, n. sp., N. nigrescens and N. californicus (Formicidae: Dorylinae), with distribution map and keys to the species of Neivamyrmex of the United States. J. Kans. Entomol. Soc. 45: 347-372 (page 364, queen described)